Reactive Groups properties.
1 Non-Oxidising Mineral Acids
2 Sulfuric Acid
3 Nitric Acid
4 Organic Acids
7 Aliphatic Amines
8 Alkanol Amines
9 Aromatic Amines
11 Organic Anhydrides
13 Vinyl Acetate
15 Substituted Allyls
16 Alkylene Oxides
20 Alcohols, Glycols
21 Phenols, Cresols
22 Caprolactam Solution
32 Aromatic Hydrocarbon Mixtures
33 Miscellaneous Hydrocarbon Mixtures
35 Vinyl Halides
36 Halogenated Hydrocarbons
38 Carbon Disulfide
40 Glycol Ethers
43 Miscellaneous Water Solutions
1 Acids, Inorganic Non-oxidizing
generally nonflammable. Generally soluble in water with the release of hydrogen ions. The resulting solutions has pH's of less than 7.0. Acids neutralize chemical bases to form salts. Neutralization occurs as the base accepts hydrogen ions that the acid donates. Neutralization can generate dangerously large amounts of heat in small spaces. Dilution in water may generate heat and sputtering. React with active metals to release hydrogen, a flammable gas. Can initiate the polymerization of certain classes of organic compounds. Reacts with cyanide compounds to release gaseous hydrogen cyanide. Generates flammable and/or toxic gases in contact with certain chemicals and strong reducing agents. Often catalyze (increase the rate) of chemical reactions. Corrosive to tissue. Acid fumes irritate sensitive tissues such the eyes and respiratory system especially severely. Have a sour taste .Turns blue litmus red EXAMPLES - Hydrochloric acid, hydroiodic acid, hydrobromic acid, hydrofluoric acid, phosphoric acid.
2 Acids Inorganic Oxidizing Same as non oxidizing. Have significant ability as oxidizing agents. but that ability varies (for example, from high for nitric acid to low for sulfuric acid and most sulfonic acids). They can react with active metals, and also many less active metals, to dissolve the metal and liberate hydrogen and/or toxic gases.. Flammable and/or toxic gases are also often generated by their reactions with certain chemicals and reducing agents. Often catalyze (increase the rate) of chemical reactions. EXAMPLES - nitric acid, perchloric acid, arsenic acid, chlorosulfonic acid, chromic acid, fluorosulfonic acid, chloric acid, nitrosulfuric acid, selenic acid, sulfurous acid.
3 Carboxylic Acids Reasonably wide flammability limits. A moderate fire hazard. Most are moderately soluble in water. Even "insoluble" carboxylic acids may absorb enough water from the air and dissolve sufficiently in it to corrode steel. Like other acids, carboxylic acids may initiate polymerization reactions. Corrosive to tissue. Most carboxylic acids are solids at room temperature; formic, acetic, propanoic, and butanoic acids are liquids. EXAMPLES - Formic acid, acetic acid, oxalic acid, propionic acid, trichlorophenoxyacetic acid, benzoic acid, citric acid, fumaric acid, the fatty acids.
4 Alcohols and Polyols Many alcohols are highly flammable . Especially dangerous are methanol and ethyl alcohol, because of their wide flammability limits. Polyols are generally combustible. Their general low volatility means that they are poorly flammable. Flammable and/or toxic gases are generated by the combination of these materials with alkali metals, nitrides, and strong reducing agents. They react with organic acids to form esters plus water. Oxidizing agents convert them to aldehydes or ketones. They exhibit both weak acid and weak base behavior. They may initiate the polymerization of isocyanates and epoxides. Alcohols and polyols vary widely in toxicity. Among the most toxic are methyl and allyl alcohol, which act as nervous system depressants. These materials are organic compounds. EXAMPLES - Ethyl alcohol, methanol, propanol, butanol, ethylene glycol, hexanol, allyl alcohol, amyl alcohol, benzyl alcohol, cyclopentanol, glycerol, isopropyl alcohol, isobutyl alcohol.
5 Aldehydes Aldehydes are volatile liquids, and are highly flammable. Dangerous ones are formaldehyde, acetaldehyde, acrolein, crotonaldehyde, and other aldehydes that have wide flammability limits. Aldehydes are frequently involved in self-condensation or polymerization reactions. These reactions are exothermic; they are often catalyzed by acid. Aldehydes are readily oxidized to give carboxylic acids. Flammable and/or toxic gases are generated by the combination of aldehydes with some chemicals and strong reducing agents. Aldehydes can react with air to give first peroxo acids, and ultimately carboxylic acids. These autoxidation reactions are activated by light, catalyzed by salts of transition metals, and are autocatalytic (catalyzed by the products of the reaction). The addition of stabilizers (anti-oxidants) to shipments of aldehydes retards autoxidation. Aldehydes act by inhalation, by ingestion, and by contact with the skin. Their exact metabolic effect depends upon the route of exposure. Among the most toxic are acrolein and crotonaldehyde, which are known carcinogens. Aldehydes are known sensitizers for small populations of humans and serve to cause chemically induced allergic reactions. The effects of these reactions can be dramatic at rather low concentrations. The effects of formaldehyde and acetaldehyde have been well documented because these aldehydes are found in many synthetic products, such as clothing, insulation, and building products. EXAMPLES - Formaldehyde, butyraldehyde, acetaldehyde, benzaldehyde, crotonaldehyde, acrolein, propionaldehyde, pentanal, valeraldehyde.
6 Amides and Imides, Organic Compounds in this group are combustible. The products of their combustion include noxious NOx. Organic amides react with azo and diazo compounds to generate toxic gases. Flammable gases are formed by the reaction of organic amides with strong reducing agents. Amides are very weak bases (weaker than water). Imides are less basic yet and in fact react with strong bases to form salts. That is, they can react as acids. Low to moderate toxicity. They act by ingestion and by contact with the skin. Most amides are solids at room temperature (exception: formamide). Amides containing five carbon atoms or fewer are soluble in water. Amides are versatile chemicals that enter into many useful reactions, especially in the fertilizer industry. Polyamides are polymers . Proteins in foods are naturally occurring polyamides; Nylon is a synthetic polymer.EXAMPLES - Urea, acetamide, acrylamide, benzamide, caprolactam, formamide, dimethylformamide, phenylurea.
7 Amines Amines are generally high-boiling liquids or solids at room temperature and are not highly flammable. Amines are combustible. The combustion of amines yields noxious NOx. Amines are chemical bases. They neutralize acids to form salts plus water. These acid-base reactions are exothermic. Flammable gaseous hydrogen is generated by amines in combination with strong reducing agents, such as hydrides. Some are very poisonous; others are only slightly toxic. Many amines are skin irritants. Some amines are known sensitizers for small populations of humans and serve to cause chemically induced allergic reactions. The effects of such reactions can be dramatic at rather low concentrations. Amines are organic compounds derived from ammonia . Many amines have unpleasantly fishy or putrid odors.EXAMPLES - Methylamine, aniline, triethanolamine, hexamethylenetetramine, cyclohexylamine, xylidine, ethylaniline, pyridine, anisidine, diphenylamine, ethylenediamine.
8 Azo, Diazo, and Azido Compounds and Organic Hydrazines, Organic Many Azo, Diazo, and Azido compounds are highly flammable/explosive (with flash points below 100 degrees F). Hydrazine and methylhydrazine are especially dangerous because of their low flash points and wide flammability limits. All compounds in this group give products that include noxious NOx. Many azides, especially the heavy metal azides, easily detonate by friction, shock, or heating. Some materials in this group can detonate. This applies in particular to organic azides that have been sensitized by the addition of metal salts or strong acids. Toxic gases are formed by mixing materials of this class with acids, aldehydes, amides, carbamates, cyanides, inorganic fluorides, halogenated organics, isocyanates, ketones, metals, nitrides, peroxides, phenols, epoxides, acyl halides, and strong oxidizing or reducing agents. Flammable gases are formed by mixing materials in this group with alkali metals. Explosive combination can occur with strong oxidizing agents, metal salts, peroxides, and sulfides. Acutely toxic by all routes of exposure. They are good oxidizing agents. EXAMPLES - Azidoacetaldehyde, azidoacetic acid, azidoacetone, aminophenylazobenzene, azobenzene, diazomethane, diazoacetonitrile, hydrazine, diazoacetaldehyde.
9 Carbamates and Esters Compounds in this group are high-boiling liquids . They are generally nonflammable, but are combustible. Combustion products include noxious NOx and carbon monoxide. Materials in this group are chemically similar to, but more reactive than amides. Like amides they form polymers such as polyurethane resins. Carbamates are incompatible with strong acids and bases, and especially incompatible with strong reducing agents such as hydrides. Flammable gaseous hydrogen is produced by the combination of active metals or nitrides with carbamates. Strongly oxidizing acids, peroxides, and hydroperoxides are incompatible with carbamates. Many carbamates are used as pesticides. These materials can be extremely toxic. They act by blocking the function of cholinesterase, an enzyme that is essential to the transmission of nerve impulses. Oral exposure is the principal concern. Absorption through the skin is slow, but dermal exposure must still be avoided because of the high toxicity. Compounds in this group are derivatives of carbamic acid (NH2COOH). The urethanes are alkyl carbamates, that is, esters of carbamic acid. EXAMPLES - Carbamic acid, ammonium carbamate, carbaryl, oxamyl, propoxur, urethane.
10Bases Materials in this group are mostly nonflammable and non-combustible. - Compounds in this group are chemically similar to sodium hydroxide (NaOH) or sodium oxide (Na2O). They neutralize acids exothermically to form salts plus water. When soluble in water they give solutions having a pH greater than 7.0. Mixing these materials with water can generate troublesome amounts of heat as the base is dissolved or diluted. Bases may initiate polymerization reactions in polymerizable organic compounds, especially epoxides). They may generate flammable and/or toxic gases with ammonium salts, nitrides, halogenated organics, various metals, peroxides, and hydroperoxides. Materials of this group often serve as catalysts. Corrosive to tissue. Solutions of bases have a bitter taste and a slippery feel; they turn red litmus blue.EXAMPLES - Sodium hydroxide, potassium hydroxide, ammonium hydroxide, barium hydroxide, barium oxide, beryllium hydroxide, calcium hydroxide, calcium oxide.
11Cyanides, Inorganic Materials in this group are generally noncombustible. Cyanides are often flammable by chemical reaction with moisture or acid; they react readily to evolve flammable HCN. Heating inorganic cyanides to decomposition liberates toxic gases and flammable gases that include HCN if traces of moisture are present. Materials in this group react slowly with water to evolve gaseous hydrogen cyanide (HCN). Acids cause the rapid evolution of HCN; carbon dioxide from the air is sufficiently acidic to liberate HCN from solutions of cyanides. Cyanides have been known to initiate polymerization reactions of epoxides. Cyanides form compounds with metal salts; heat and hydrogen production may accompany these reactions. Some cyanides can detonate when exposed to shock, heat, or friction. Many of these materials are corrosive to tissue and are extremely toxic by all routes of exposure. Cyanides bind hemoglobin in the blood, and many enzymes are inactivated in the presence of cyanide. Cyanogen chloride and bromide are lachrymators. Cyanides are used as pesticides and in chemical synthesis.EXAMPLES - Barium cyanide, calcium cyanide, copper cyanide, cyanogen chloride, hydrogen cyanide, lead cyanide, potassium cyanide, silver cyanide.
12Thiocarbamate Esters and Salt/Dithiocarbamate Esters and Salts Materials in this group are combustible. Poisonous gases are generated by the thermal decomposition of compounds of this class, including carbon disulfide, oxides of sulfur, oxides of nitrogen, hydrogen sulfide, ammonia, and methylamine. Many materials in this group slowly decompose in aqueous solution to form carbon disulfide and methylamine or other amines. Such decompositions are accelerated by acids. TOXICITY - The slow release of poisonous gases from hydrolysis of many compounds in this group requires the use of respirators during handling. Poisoning can also occur by ingestion and absorption through the skin. These chemicals are used in the synthesis of polymers and in agriculture as pesticides, soil fumigants, and seed disinfectants.EXAMPLES - Cycloate, ethyl dithiocarbamate, ferbam, maneb, ethylenebisdithiocarbamate, metham sodium, nabam, thiram, sodium dimethyldithiocarbamate, thiobencarb, zineb, zinc diethyldithiocarbamate.
13Esters Many esters are flammable or highly flammable. All are capable of being combustible and yield toxic gases such as carbon monoxide when burned. Some may spontaneously heat and ignite if stored wet and hot. Materials in this group react with acids to liberate heat along with alcohols and acids. Strong oxidizing acids may cause a vigorous reaction that is sufficiently exothermic to ignite the reaction products. Heat is also generated by the interaction of esters with caustic solutions. Flammable hydrogen is generated by mixing esters with alkali metals and hydrides. Inhalation of the fumes from some esters irritates the mucous membranes. Esters have low to moderate toxicity via dermal and oral exposure. Some esters are used as flavoring agents in foodstuffs. Their names are derived from the names of the acid and alcohol from which they are synthesized. Esters include the edible fats and oils, which are mixed esters between the triol glycerol and fatty acids. Esters are prominent in the perfumery and flavoring industry. They are used to manufacture synthetic fibers such as polyester and plastics.EXAMPLES - Ethyl acetate, methyl acrylate, cyclohexyl acrylate, butyl propionate, butyl lactate, butyl formate, butyl acetate, benzyl acetate, amyl butyrate, amyl acetate, allyl acetate.
14Ethers Low-molecular-weight ethers are flammable gases (methyl ether) or liquids (methyl ethyl ether or ethyl ether) that can produce explosive mixtures when they evaporate and mix with air. Ethers form peroxides if exposed to oxygen or air during storage; the ether peroxides can detonate with friction, shock, or heat, releasing enough energy to start a secondary fire in the unperoxidized ether.- Ethers tend to form unstable peroxides when exposed to oxygen. Ethyl, isobutyl, ethyl tert-butyl, and ethyl tert-pentyl ether are particularly hazardous in this respect. Ether peroxides can sometimes be observed as clear crystals deposited on containers or along the surface of the liquid. Ethers can act as bases. They form salts with strong acids . Ethers may react violently with strong oxidizing agents. Ethers are moderately toxic. The lower-molecular weight ethers are powerful rapid-acting narcotics by inhalation. Toxic effects from these compounds are usually acute not chronic. The swallowing of one ounce of a liquid ether may be fatal. EXAMPLES - Phenyl ether, ethyl ether, allyl ethyl ether, anisidine, anisole, butyl methyl ether, butyl vinyl ether, diallyl ether, isopropyl ether, divinyl ether, methyl ether, isobutyl.
16Hydrocarbons, Aromatics Aromatic hydrocarbons are all combustible. The lightest members of this class, benzene and substituted benzenes, have high enough vapor pressures and low enough flash points to be vapor explosion hazards. Vigorous reactions, sometimes amounting to explosions, can result from the contact between these materials and strong oxidizing agents. They can react exothermically with bases . Many aromatic hydrocarbons are poisons by inhalation and irritants to the skin and eyes. Some are poisons by skin contact. Aromatic hydrocarbons are very often carcinogenic (benzene is an example). Compounds in this group contain the benzene nucleus. In benzene six carbon atoms form a ring maintained by alternating single and double bonds; each carbon atom is also bonded to a hydrogen atom. Aromatic hydrocarbons possess a single benzene nucleus with side-groups replacing one or more of the hydrogen atoms or in fused sets of two or more rings. They are common air contaminants.EXAMPLES - Benzene, toluene, naphthalene, pyrene, anthracene, chrysene, acenaphthylene, xylene, benzo[a]pyrene, biphenyl, cumene, fluorene, phenanthrene.
17Halogenated Organic Compounds The flammability of these materials is variable. The low-molecular-weight materials (gases and liquids) are generally dangerously flammable. Simple aromatic halogenated organic compounds are very unreactive; halogenated aliphatic compounds are moderately or very reactive. Halogenated acetylene compounds are unstable and should be treated as explosives. Low molecular weight haloalkanes are highly flammable and can react with some metals to form dangerously products. Low molecular weight haloalkenes are highly flammable, peroxidizable and may polymerize violently. They may react violently with aluminum. Materials in this group are incompatible with strong oxidizing and reducing agents. Also, they are incompatible with many amines, nitrides, azo/diazo compounds, alkali metals, and epoxides. Many halogenated hydrocarbons have moderate to high toxicity by inhalation. The brominated materials tend to be particularly toxic. Much of the toxicity is due to the fact that these substances are not metabolized, but persist and accumulate in fatty tissues (they tend to be fat-soluble). The combustion of chlorinated organic compounds may produce poisonous phosgene gas . Other materials formed by incomplete combustion are classes of chlorinated organic compounds, chlorodibenzodioxins and chlorodibenzofurans. These compounds cause cancer in laboratory tests. This class of compounds is extremely important in industry in the production of polymers, pesticides, and fire retardants.EXAMPLES - Vinyl chloride, vinylidene chloride, chlorobenzene, trichlorobenzene, polychlorinated biphenyls (PCBs), methylene chloride, chloroform, chloroisoprene, trichlorobenzene.
18Isocyanates and Isothiocyanates, Organic These materials usually have low vapor pressures and are non-flammable. All are combustible. They evolve poisonous gases such as HCN, NOx, SOx, and CO when they burn. Isocyanates and thioisocyanates are incompatible with many classes of compounds, reacting exothermically to release toxic gases. Reactions with amines, aldehydes, alcohols, alkali metals, ketones, mercaptans, strong oxidizers, hydrides, phenols, and peroxides can cause vigorous releases of heat. Acids and bases initiate polymerization reactions in these materials. Some isocyanates react with water to form amines and liberate carbon dioxide. Polyurethanes are formed by the condensation reaction of diisocyanates with, for example, ethyl glycol. Upon direct exposure members of this chemical class have moderate toxicity. Vapors irritate mucous membranes. Organic isocyanates and isothiocyanates are known sensitizers for a small percentage of people, causing chemically induced allergic reactions. The effects of these reactions can be dramatic at rather low concentrations. No organic cyanates exist in the monomeric state. EXAMPLES - Phenylene diisocyanate, cyclohexane diisocyanate, naphthalene diisocyanate, cyclohexyl isocyanate, ethyl isocyanate, isobutyl isocyanate, isopropyl isocyanate, methyl isocyanate, n-butyl isocyanate, phenyl isocyanate, propyl isocyanate.
19Ketones Many low-molecular-weight ketones (such as acetone and methyl ethyl ketone) are highly flammable. Most ketones are liquids with relatively high vapor pressures, capable of forming explosive mixtures with air. Materials in this group are reactive with many acids and bases liberating heat and flammable gases (e.g., H2). The amount of heat may be sufficient to start a fire in the unreacted portion of the ketone. Ketones react with reducing agents such as hydrides, alkali metals, and nitrides to produce flammable gas (H2) and heat. They react violently with aldehydes n HNO3. Some ketones are highly volatile and may have narcotic or anesthetic effects. Entry into the body occurs by absorption through the skin as well as inhalation and ingestion. These materials are generally used as solvents in the paint, textiles, plastics, and lacquer industries.EXAMPLES - Acetone, acetophenone, cyclohexanone, diethylketone, diisobutylketone, dipropylketone, isophorone, methyl acetone, methyl amyl ketone, methyl butanone, methyl ethyl ketone.
20Sulfides, Organic The low-molecular-weight gaseous and liquid sulfides (such as methyl mercaptan or ethyl mercaptan) are extremely flammable, but flammability diminishes with increasing molecular weight. The products of combustion include sulfur dioxide. Materials in this group are incompatible with acids, diazo and azo compounds, halocarbons, isocyanates, aldehydes, alkali metals, nitrides, hydrides, and other strong reducing agents. Reactions with these materials generate heat and in many cases hydrogen gas. Many of these compounds may liberate hydrogen sulfide upon decomposition or reaction with an acid. Most organic sulfides are toxic by inhalation. In general, they are stenches. Thus methyl mercaptan is added to natural gas (which is odorless) to assist in the detection of leaks. These chemicals are used in industrial synthesis of chemicals, and are important as catalysts, as additives in petroleum and natural gas, and as pesticides.EXAMPLES - Amyl mercaptan, butyl mercaptan, carbon disulfide, diamyl sulfide, dimethyl sulfide, ethyl mercaptan, propyl mercaptan, methyl mercaptan.
21Metals, Alkali, Very Active The alkali metals are nonflammable, but they are combustible. They may also burn in carbon dioxide and in nitrogen. Their reaction with water is violently rapid and quite exothermic. It produces gaseous hydrogen and other products. The heat that is generated is sufficient to melt the unreacted metal, ignite the liberated hydrogen and ignite the metal itself. Materials in this group react, usually vigorously, with any substance having active hydrogen atoms to liberate gaseous hydrogen. This includes alcohols and acids, and most importantly, water. They corrode rapidly on contact with the air, becoming coated with white oxides and peroxides. As a practical matter, most other organic compounds, including ethers, are wet enough (carry enough water as an impurity) to cause heating and liberation of gases in contact with alkali metals. Alkali metals and alloys containing alkali metals are all powerful reducing agents. All the materials in this group react with moisture to generate caustic products. Contact with these metals with the skin can cause chemical burns by the action of these products and thermal burns from the heat of the reaction.EXAMPLES - Cesium, lithium, potassium, sodium.
22Metals, Elemental & Powder, Active Materials in this group are combustible, especially as finely divided powders. Powdered iron has exploded in the presence of air, moisture, and small amounts of organic impurities. All of these materials are reducing agents and tend to react with oxidizing agents. Their reactivity is strongly influenced by their state of subdivision: in bulk they often resist chemical combination; in powdered form they may react very rapidly. Thus, bulk aluminum is used as a structural metal, but finely divided aluminum is pyrophoric. Many of these materials react exothermically with compounds have active hydrogen atoms (such as acids and water) to form flammable hydrogen gas and caustic products. Materials in this group may react with azo/diazo compounds to form explosive products. These metals and the products of their corrosion by air and water can catalyze polymerization reactions in several classes of organic compounds; these polymerizations sometimes proceed rapidly or even explosively. Some metals in this group form explosive products with halogenated hydrocarbons. Caustic products formed from the corrosion of some of these metals by air or water can cause chemical burns. Inhalation of metal powders, dusts and fumes can cause serious symptoms. Even metals that are less toxic by inhalation (such as zinc) often contain toxic impurities (cadmium, antimony, arsenic, and lead). Iron dust causes conjunctivitis and lodges in the lungs to induce cancers. The metals are used chemically as reducing agents. EXAMPLES - Aluminum, aluminum ferrosilicon, antimony, beryllium, calcium silicon, cerium, cobalt, gallium, hafnium, iron, magnesium alloy, nickel catalyst, selenium, silicon, silver, strontium, titanium, zinc, zirconium.
23Metals, Less Reactive Nonflammable. Not reactive enough to burn in air, even if finely divided. Metals in this group can react exothermically with oxidizing acids to form noxious gases. Many catalyze polymerization and other reactions, particularly when finely divided Metals in this group have been known to react with halogenated hydrocarbons, sometimes forming explosive compounds (for example, copper dissolves when heated in carbon tetrachloride). They are less reactive in massive form (sheet, rod, or drop) than when finely divided. Fumes from the hot metals are toxic by inhalation. EXAMPLES - Copper, lead, silver, gold.
26Nitriles Many of the compounds of this group are highly flammable, especially substances such as acrylonitrile and acetonitrile that have low flash points and relatively wide flammability concentration limits. All are combustible. The incomplete combustion of these materials produces significant amounts of gaseous hydrogen cyanide. When heated to decomposition, nitriles emit highly toxic fumes. Nitriles may polymerize in the presence of metals and some metal compounds. They are incompatible with acids; mixing nitriles with strong oxidizing acids can lead to extremely violent reactions. Nitriles are generally incompatible with other oxidizing agents such as peroxides and epoxides. The combination of bases and nitriles can produce hydrogen cyanide. Nitriles are hydrolyzed in both aqueous acid and base to give carboxylic acids (or salts of carboxylic acids). These reactions generate heat. Nitriles can react vigorously with reducing agents. Acetonitrile and propionitrile are soluble in water. They are absorbed by inhalation, ingestion and by contact with the skin. Other nitriles vary in toxicity, with some approaching the cyanides in toxicity.The most important use of these materials is in the production of nitrile rubber, which is a copolymer of acetonitrile with butadiene. Nitriles such as cyanogen are used in organic synthesis, fumigants, and rocket propellant materials.EXAMPLES - Pentenenitrile, acetonitrile, acrylonitrile, benzonitrile, butyronitrile, cyanoacetic acid, isobutyronitrile, lactonitrile, methacrylonitrile, propionitrile.
27Nitrites, Nitrates, and Nitro Compounds, Organic Most materials in this group are technically of low flammability. However, they are often chemically unstable and subject, in widely varying degree, to explosive decomposition. As oxidizing agents, they are often used in combination with reducing agents in explosive mixtures. Or, as in the primary explosive nitroglycerine, the oxidizing and reducing behavior is present internally in the same molecule. Because many of these substances are extremely sensitive to shock, friction, and heat, they are mixed with unreactive material to make them less dangerous. Materials in this group range from slight to strong oxidizing agents. If mixed with reducing agents, including hydrides, sulfides and nitrides, they may begin a vigorous reaction that culminates in a detonation. The aromatic nitro compounds may explode in the presence of a base such as sodium hydroxide or potassium hydroxide even in the presence of water or organic solvents. Nitroalkanes are milder oxidizing agents, but still react violently with reducing agents at higher temperature and pressures. Nitroalkanes react with inorganic bases to form explosive salts. The presence of metal oxides increases the thermal sensitivity of nitroalkanes. Many of the compounds in this group are extremely toxic. Chronic dermal and inhalation exposure causes hepatitis.The biggest use of compounds in this group is in military and commercial explosives. EXAMPLES - Nitropyrene, nitroglycerine, dinitrophenol, trinitrotoluene, dinitrotoluene, nitropropane, amyl nitrate, nitrobenzene, dinitrocresol, dinitroaniline, ethyl nitrate, glyceryl trinitrate, dinitrobenzene, nitrocellulose, nitroanisole, nitrocyclohexane, nitroethane.
28Hydrocarbons, Aliphatic Unsaturated The lightest-molecular weight substances in this group are highly flammable and pose significant vapor cloud explosion hazards (examples are ethylene and propylene). All are combustible. The unsaturated aliphatic hydrocarbons are generally much more reactive than the alkanes, which are saturated aliphatic hydrocarbons. Reducing agents can react exothermically to release gaseous hydrogen gas. In the presence of various catalysts (such as acids) or initiators, compounds in this class can undergo very exothermic addition polymerization reactions. Many of these compounds undergo autoxidation upon exposure to the air to form explosive peroxides (this process generally occurs slowly). These peroxide and polyperoxide substances are usually extremely unstable and liable to detonation. The peroxidation of butadiene has been involved in several serious industrial explosion accidents. Unsaturated aliphatic hydrocarbons are characterized by straight or branched carbon chains containing double and triple bonds between the carbon atoms. They are also known as alkenes (or olefins) and alkynes. Their physical state at room conditions changes with increasing molecular weight from gaseous to waxy solid. They are used in making rubber and plastics and in organic synthesis.EXAMPLES - Butadiene, pentadiene, butyne, butene, pentene, acetylene, amylene, cycloheptatriene, cycloheptane, cyclohexane, cyclooctadiene, isobutylene, dipentene, ethylene, hexene, isohexene, isoprene, methyl pentadiene.
29Hydrocarbons, Aliphatic Saturated The lowest-molecular-weight compounds pose significant vapor cloud explosion hazards. Ethane, propane, and butane are gases that have been involved in many explosions. All aliphatic saturated hydrocarbons are combustible. Materials in this group may be incompatible with strong oxidizing agents like nitric acid. Charring of the hydrocarbon may occur followed by ignition of unreacted hydrocarbon and other nearby combustibles. When heated sufficiently or when ignited in the presence of air, oxygen or strong oxidizing agents, they burn exothermically to produce carbon dioxide and water. Compounds in this group have low toxicity. They act as asphixiants. Compounds in this group are characterized by straight or branched carbon chains with the generic formula C(n)H(2n+2). They also known as alkanes or paraffins. Their physical form varies with increasing molecular weight from gaseous (methane) to solid. The solids are waxy and soft.EXAMPLES - Propane, butane, pentane, cyclobutane, cycloheptane, hexane, cyclohexane, isopentane, cyclopentane, decane, dimethylpropane, ethane, heptane, isobutane, dodecane, isohexane, methane, isododecane.
30Peroxides, Organic Generally, materials in this group are readily combustible. They behave as strong oxidants and therefore accelerate the combustion of other materials by providing molecular oxygen to the combustion site. Many peroxides are unstable and subject to explosive decomposition when shocked, heated, or rubbed. Explosions of peroxides have caused many fatal accidents. Peroxides are good oxidizing agents. Organic compounds can ignite on contact with concentrated peroxides. Strongly reduced material such as sulfides, nitrides, and hydrides may react explosively with peroxides. There are few chemical classes that do not at least produce heat when mixed with peroxides. Many produce explosions or generate gases (toxic and nontoxic). Generally, dilute solutions of peroxides (<70%) are safe, but the presence of a catalyst (often a transition metal such as cobalt, iron, manganese, nickel, or vanadium) as an impurity may even then cause rapid decomposition, a build-up of heat, and even an explosion. Solutions of peroxides often become explosive when evaporated to dryness or near-dryness. Often highly toxic and irritating to the skin, eyes, and mucous membranes. Some organic compounds form dangerous levels of explosive peroxides by autoxidation when exposed to the air during storage. These peroxides generally form slowly and are explosive when taken to dryness. Many peroxide solutions are inhibited to prevent, decomposition to give oxygen and other products. Such reactions are often catalyzed by impurities in the absence of inhibition. peroxides are widely used as polymerization initiators. Peroxides are used in the paper industry (for bleaching), in making textiles (for bleaching), as oxidizers in organic synthesis reactions, as blowing agents, and in propellant formulations.EXAMPLES - Benzoyl peroxide, peroxybenzoic acid, acetyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, octanyl peroxide, diacetone alcohol peroxide.
31Phenols, Cresols Materials in this group are combustible. These materials are incompatible with strong reducing substances such as hydrides, nitrides, alkali metals, and sulfides. Flammable gas (H2) is often generated, and the heat of the reaction may ignite the gas. Heat is also generated by the acid-base reaction between phenols and bases. Such heating may initiate polymerization of the organic compound. Phenols are sulfonated very readily (for example, by concentrated sulfuric acid at room temperature). The reactions generate heat. Phenols are also nitrated very rapidly, even by dilute nitric acid. Nitrated phenols often explode when heated. Many of them form metal salts that tend toward detonation by rather mild shock.Moderate to high toxicity. Some of the more toxic members of this class of compounds are the chlorinated and nitro-substituted phenols that are used as pesticides and antibacterials (dinoseb, creosote, chlorinated phenol, p-nitrophenol). Phenol is strongly irritating to the skin. Phenols are used in many organic syntheses, and the making of phenol/formaldehyde resins and polycarbonate resins. EXAMPLES - phenol, cresol, dinitrophenol, phenylphenol, dinitrocresol, alkyl phenol, aminochlorophenol, aminophenol, amyl phenol, butyl phenol, catechol, creosote, picric acid, resorcinol, trichlorophenol, dichlorocresol.
32Phosphates and Thiophosphates, Organic
These materials are combustible. Burning them generates highly toxic fumes of phosphorus oxides and (in the case of the thiophosphates) sulfur oxides. Many fire-retardant foams are organophosphate-based and act to lay down a protective layer that excludes oxygen. Materials in this group are susceptible to formation of highly toxic and flammable phosphine gas in the presence of strong reducing agents such as hydrides. Partial oxidation by oxidizing agents may result in the release of toxic phosphorus oxides. The pyrophosphate esters (such as tetraethyl pyrophosphate) are highly toxic. These derivatives form the basis of a group of insecticides. They interfere with normal nerve transmission by inhibiting cholinesterase. These pesticides should be handled with great care (when released to the environment they are rapidly degraded). Other organophosphates behave similarly.used as plasticizers, insecticides, resin ingredients, flame retardants, fertilizer EXAMPLES - Acephate, chlormephos, chlorfenvinfos, coumaphos, demeton, diazinon, dimefox, dimethoate, ethoprophos, fenamiphos, fonofos, hexaethyl tetraphosphate, isofenphos, isofluorphate, leptophos, merphos, mevinphos, monocrotophos, profenofos, propetamphos.
33Sulfides, Inorganic The only highly flammable member of this group is hydrogen sulfide. It poses a particular danger because of its relatively wide flammability limits. However, some other inorganic sulfides can heat spontaneously and even ignite if exposed to moisture. Materials in this group are generally basic and therefore incompatible with acids. Many of these compounds are reducing agents and therefore react vigorously with oxidizing agents, including inorganic oxoacids, organic peroxides and epoxides. Simple salts of sulfides (such as sodium, potassium, and ammonium sulfide) react vigorously with acids to release hydrogen sulfide gas. Many of the members of this group behave as strong bases. Therefore, direct dermal exposure by these materials may cause severe burns. Hydrogen sulfide is a toxic gas that irritates the eyes and mucous membranes at concentrations of around 50 ppm (sensitivity varies considerably from person to person). Most of the symptoms of hydrogen sulfide poisoning are reversible if the victim is quickly exposed to fresh air. The gas causes death at concentrations of around 1,000 ppm. Compounds in this group tend to have very unpleasant odors.EXAMPLES - Ammonium hydrosulfide, sodium hydrosulfide, ammonium sulfide, antimony sulfide, arsenic sulfide, arsenic trisulfide, lead sulfide, hydrogen sulfide, mercuric sulfide, phosphorus heptasulfide, potassium hydrosulfite, potassium sulfide, selenium disulfide, sodium sulfide.
34Epoxides Epoxides present serious fire and explosion hazards. Vapors are heavier than air, so flashback to source is a danger, along with rupture of a closed container. Materials in this group are highly reactive. They polymerize in the presence of catalysts or when heated. These polymerization reactions can be violent. Compounds in this group react with acids, bases, and oxidizing and reducing agents. They react, possibly violently with water in the presence of acid and other catalysts. Corrosive and irritating to mucous membranes, eyes, respiratory tract. Upon direct contact with skin will cause irritation. Toxic when absorbed through the skin. Fumes are serious inhalation hazard. Certain people have a particular sensitivity to epoxides and the resins they form. They are used in organic synthesis and are polymerized to form epoxy resins. Also used as solvents in synthetic reactions such as gums, cellulose esters, paints, varnishes, enamels, and lacquers. EXAMPLES - Butylene oxide, ethylene oxide, propylene oxide, diepoxy butane, endrin, epibromohydrin, styrene oxide, heptachlor epoxide.
35Metal Hydrides, Alkyls and Aryls Many of these compounds are pyrophoric (flammable by spontaneous chemical reaction in air). They produce highly flammable gases in the presence of acid. The metal hydrides are combustible. Combustion of all compounds in this class produces irritating and toxic gases. Materials in this group are reducing agents and react rapidly and dangerously with oxygen and with other oxidizing agents, even weak ones. Thus, they are likely to ignite on contact with alcohols. Hydrides are incompatible with acids, alcohols, amines, and aldehydes.TOXICITY - Extremely corrosive and irritating to mucous membranes, eyes, and the respiratory tract. Fumes are a serious inhalation hazard. Some of these materials are gases and are extremely poisonous by inhalation. Compounds in this group are generally used as reducing agents in industrial chemical synthesis and may act as catalysts.EXAMPLES - Aluminum borohydride, aluminum hydride, amyl trichlorosilane, calcium hydride, diborane, lithium aluminum hydride, lithium hydride, magnesium hydride, potassium borohydride, sodium borohydride, sodium hydride.
37Anhydrides Except for acetic anhydride, these materials are not flammable but are combustible. The products of combustion are noxious. Organic anhydrides react exothermically with water. The reactions are sometimes slow, but can become violent when local heating accelerates their rate. The rate of reaction with water is also accelerated by acids. Compounds from this group are incompatible with acids, strong oxidizing agents, alcohols, amines, and bases. Extremely corrosive and irritating to mucous membranes, eyes, respiratory tract. Burns the skin. Fumes are serious inhalation hazard. Compounds in this group are used in organic synthesis and as dehydrating agents in nitration, sulfonation, and other reactions. EXAMPLES - Acetic anhydride, butyric anhydride, isobutyric anhydride, maleic anhydride, methacrylic anhydride, phthalic anhydride, propionic anhydride
38Salts, Acidic Inorganic/Organic None of these materials are highly flammable. Inorganic salts are generally noncombustible as well. Salts containing organic groups are in principle combustible, although they may burn with difficulty. Materials in this group are generally soluble in water. The resulting solutions contain moderate concentrations of hydrogen ions and have pH's of less than 7.0. They react as acids to neutralize bases. These neutralizations generate heat, but less or far less than is generated by neutralization of inorganic acids, inorganic oxoacids, and carboxylic acid. They usually do not react as either oxidizing agents or reducing agents but such behavior is not impossible. Many of these compounds catalyze organic reactions. Solutions of these materials are generally corrosive to skin and irritating to mucous membranes.EXAMPLES - Ferric chloride, aluminum sulfate, ammonium bromide, antimony tribromide, cupric oxalate, ferric sulfate.
39Salts, Basic Inorganic/Organic None of these materials are highly flammable. Inorganic salts are generally noncombustible as well. Salts containing organic groups are in principle combustible, although they may burn with difficulty. Materials in this group are generally soluble in water. The resulting solutions contain moderate concentrations of hydroxide ions and have pH's greater than 7.0. They react as bases to neutralize acids. Solutions of these materials can be corrosive to skin and irritating to mucous membranes.EXAMPLES - Aluminum phosphate, aluminum carbonate, ammonium citrate, ammonium formate, ammonium oxalate, cadmium stearate, calcium phosphate, copper formate, lead phosphate, mercurous acetate, nickel acetate, nickel formate, potassium oxalate.
40Acid Halides These materials are flammable and pose a vapor cloud explosion threat. Vapors may flashback to source and cause a violent rupture of a closed container. Combustion of acid chlorides produces hydrochloric acid and phosgene; toxic and irritating gases are also generated from the combustion of acid bromides and iodides. Materials in this group are water reactive; some are violently reactive. They are incompatible with strong oxidizing agents, alcohols, amines, alkali. Extremely corrosive and irritating to mucous membranes, eyes, and the respiratory tract. Upon direct contact with skin, they will cause severe burns. Fumes are a serious inhalation hazard. These compounds are used in industrial synthesis of organic compounds, especially acetyl compounds, and to eliminate all traces of water from organic liquids.EXAMPLES - Acetyl bromide, acetyl chloride, acetyl iodide, benzoyl chloride, fumaryl chloride, isobutyrl chloride, methacryloyl chloride, phenacetyl chloride.
42Organometallics Many organometallic compounds are flammable or highly flammable; sometimes they are pyrophoric. They are generally combustible. Strongly reactive with many other groups. Incompatible with acids and bases. Organometallics are good reducing agents and therefore incompatible with oxidizing agents. Often reactive with water to generate toxic or flammable gases. Organometallics containing halogens (fluorine, chlorine, bromine, iodine) bonded to the metal typically will generate gaseous hydrohalic acids (HF, HCl, HBr, HI) with water, with heat released. Generally highly toxic. Often react on contact with tissues to give toxic products. Irritating to skin, eyes, and mucous membranes. Can damage lung tissue and the liver.EXAMPLES - Bis(1,5-cyclooctadiene)nickel, bis(cyclopentadienyl)chromium, bis(cyclopentadienyl)vanadium chloride, bis(cyclopentadienyl)vanadium dichloride, bis(tributyltin)oxide, chromium carbonyl, cobalt carbonyl, cobaltocene, dibutyltin diacetate, ethyl aluminum chloride.
44Inorganic Oxidizing Agents Materials in this group do not burn in themselves, but enhance the combustion of other substances. Inorganic oxidizing agents can react with reducing agents to generate heat and products that may be gaseous (causing pressurization of closed containers). The products may themselves be capable of further reactions (such as combustion in the air). The chemical reduction of materials in this group can be rapid or even explosive, but often requires initiation (heat, spark, catalyst, addition of a solvent). Explosive mixtures of inorganic oxidizing agents with reducing agents often persist unchanged for long periods if initiation is prevented. Such systems are typically mixtures of solids, but may involve any combination of physical states. Some inorganic oxidizing agents are salts of metals that are soluble in water; dissolution dilutes but does not nullify the oxidizing power of such materials. Organic compounds in general are have some reducing power and can in principle react with compounds in this class. Actual reactivity varies greatly with the identity of the organic compound. Inorganic oxidizing agents can react violently with active metals, cyanides, esters, and thiocyanates. Explosives often consist of an inorganic oxidizing agent mixed in intimate contact with a reducing agent. Gunpowder is such a mixture. Other examples are a mixture of sugar (an organic compound) plus sodium chlorate and magnesium (an inorganic reducing agent) plus barium peroxide. The strongly oxidizing elements oxygen and fluorine are classified here. Inorganic oxidizing agents that are also acids (such as nitric and perchloric acids) are not included in this group. Most are toxic by ingestion; degree varies widely. Inorganic oxidizing agents include nitrates, nitrites, permanganates chromates, bromates, iodates, chlorates, perchlorates, chlorites, hypochlorites, inorganic peroxides, and certain oxides. The most dangerous oxidizing agents are the chlorites, chlorates, and perchlorates, in that order. Acidic media favor reactions in which these substances act as oxidizing agents.EXAMPLES - Ammonium dichromate, ammonium nitrate, ammonium perchlorate, ammonium permanganate, barium bromate, barium chlorate, barium peroxide, cadmium chlorate, calcium chlorate, calcium chromate, calcium perchlorate, chromium nitrate, cobalt nitrate.
45Inorganic Reducing Agents Nonflammable. Compounds in this class react with oxidizing agents to generate heat and products that may be flammable, combustible, or otherwise reactive. Their reactions with oxidizing agents may be violent. Sulfites and hydrosulfites (dithionites) can react explosively with strong oxidizing agents. Sulfites generate gaseous sulfur dioxide in contact with oxidizing acids and non-oxidizing acids. Most are toxic by ingestion; degree varies widely.Sulfur and other non-metallic, elemental reducing agents appear here.EXAMPLES - Ammonium bisulfite, ammonium sulfite, ammonium thiosulfate, arsenic sulfide, arsenic trisulfide, calcium dithionite, chromous chloride, ferrous chloride, ferrous oxalate.
46Inorganic Compounds/Neither Reducing nor Oxidizing These compounds are nearly all nonflammable. Some are combustible; the majority are not. Those that are combustible are usually only poorly combustible. These materials have weak oxidizing or reducing powers. . The majority of compounds in this class are slightly soluble or insoluble in water. Most are toxic by ingestion; degree varies widely. Arsenates and arsenites are often quite toxic by skin contact, and inhalation of dust.EXAMPLES - Iron(III) oxide, sodium chloride, lead sulfate, lead arsenate, aluminum fluoride, aluminum oxide, asbestos, barium chloride, beryllium sulfate, cadmium bromide, cadmium stearate, calcium chloride.
47CFCs and HCFCs (chlorofluorocarbons and chlorofluorohydrocarbons) These compounds are generally not flammable; some are combustible, but usually only poorly. These materials are chemically inert in many situations, but can react violently with strong reducing agents such as the very active metals and the active metals. They suffer oxidation with strong oxidizing agents and under extremes of temperature. Low toxicity. In these compounds chlorine and fluorine replaces some hydrogen in a hydrocarbon. The presence of fluorine lowers the reactivity relative to unfluorinated compounds. This category also includes compounds in which bromine replaces some of the chlorine atoms. All compounds are gases under standard conditions. EXAMPLES - 1,1,2-trichloro-1,2,2-trifluoroethane, 1,2-dichloro-1,1,2,3,3-pentafluoropropane. 1-chloro-1,1-difluoroethane, 1-chloro-1,1,2,2-tetrafluoroethane, 1-chloro-2,2,2-trifluoroethane, 1,1-dichloro-1,2,2-trifluoroethane.
Nitrides, Phosphides, Carbides, and Silicides, Inorganic These compounds react readily with oxygen or air. They are often pyrophoric, especially if finely divided. The transition metal nitrides are often explosively unstable. Materials in this group are reducing agents. They generate flammable or noxious gases in contact with water. Many nitrides react with moisture to evolve gaseous ammonia, which is toxic and combustible. Phosphides react quickly upon contact with moisture or acids to give the very toxic gas phosphine; phosphides also can react vigorously with oxidizing materials. Inorganic amides react with moisture to evolve ammonia. Inorganic carbides react with water to generate flammable gases. The transition metal nitrides react violently with water forming the metal hydroxides and ammonia. In general, materials in this group are incompatible with oxidizers such as atmospheric oxygen. They are violently incompatible with acids, particularly oxidizing acids. Tend to react with water to give corrosive or toxic products. Corrosive to skin and mucous membranes.EXAMPLES - Sodium amide, calcium carbide, magnesium silicide, lithium nitride, calcium nitride, chromium nitride. aluminum carbide, aluminum phosphide, calcium phosphide, calcium silicide, magnesium aluminum phosphide, magnesium phosphide, potassium phosphide.
55 Chlorosilanes Flammable or pyrophoric. Chlorosilanes react with water, moist air, or steam to produce heat and toxic, corrosive fumes of hydrogen chloride. They may also produce flammable gaseous H2. They can serve as chlorination agents. Chlorosilanes react vigorously both organic and inorganic acids and with bases to generate toxic or flammable gases. Poisonous by ingestion and inhalation and a poisonous irritant to the skin, eyes, and mucous membranes. The toxicity is based on that of HCl, which forms by the reaction of chlorosilanes with water.EXAMPLES - Allyltrichlorosilane, methyldichlorosilane, silicon tetrachloride, vinyl trichlorosilane, trimethylchlorosilane, trichlorosilane, propyltrichlorosilane, phenyltrichlorosilane, methyl trichlorosilane.
59 Halogenating Agents, Strong These compounds are technically nonflammable, but are combustible. They can support the combustion of other materials. Fluorinating agents can react violently with halide salts. Many of these compounds are water-reactive and air-reactive. Generally toxic.EXAMPLES - Antimony pentafluoride, molybdenum pentachloride, nitrogen fluoride oxide, antimony pentachloride, tungsten hexafluoride, tellurium hexafluoride, sulfur tetrafluoride, sulfur monochloride, silicon tetrafluoride, phosphorus pentafluoride.
CHEMICAL DEFNITIONS :--
INABILITY TO UNDERSTAND MSDS SHEETS / MFAG /EmS WHEN HANDLING TOXIC / CARCINOGENIC IS AN OFFENCE.
Acid A substance that donates hydrogen ions that can be accepted by a base.
Aerobic Living, growing, and reproducing in an environment with air or oxygen present. E.g., aerobic bacteria.
Air-reactive Likely to react rapidly or violently with dry or moist air. May apply to the toxic and corrosive fumes generated when a chemical is exposed to air.
Alkali A general description given to strong bases, including the hydroxides and carbonates of the "alkali metal" or group 1A of the Periodic Table. Examples include sodium hydroxide, potassium hydroxide, etc. A synonym for the strong alkalis is caustics.
Alkaline Having a high concentration of hydroxide ions in aqueous solution (i.e., a high pH). Strongly alkaline aqueous solutions are very corrosive to skin, metal, and other materials.
Alkane An organic compound that contains only hydrogen and carbon and has only single bonds
Alkene A hydrocarbon that contains at least one carbon-carbon double bond.
Alkyne Hydrocarbons that contain at least one carbon-carbon triple bond.
Amorphous Lit. "without shape." A substance that lacks structure. Generally, amorphous solids lack three-dimensional crystal structure. Most liquids are amorphous, with exceptions such as liquid water, which is highly structured.
Anaerobic Living, growing, and reproducing in an environment without air or oxygen. E.g., anaerobic bacteria.
Anhydrous Lit. "without water." A substance that has no water associated with it in the form of hydrate or water of crystallization. Examples include anhydrous ammonia and aluminum chloride.
Anion An atom or group of atoms having a negative net charge.
Antioxidant A chemical substance that reduces the tendency of oxygen to chemically combine with hydrocarbons in commercial products such as vegetable oils, rubber, petroleum products, and animal fats. These antioxidants are organic compounds added to mixtures in low concentrations.
Aqueous Consisting largely of water or dissolved in water.
Aromatic compound An unsaturated organic compound containing one or more rings of carbon atoms in which single and double bonds alternate.
Asphixiant A gas that is non-toxic but may kill if it accumulates in a confined space and is breathed at high concentrations, because it drives out oxygen-containing air.
Autoignition temperature Or ignition point. At some minimum temperature, a substance will catch fire in the absence of an ignition source such as a flame or spark. That temperature is the substance's autoignition temperature.
Autoxidation The tendency of oxygen to chemically combine with hydrocarbons in commercial products such as vegetable oils, rubber, petroleum products, and animal fats.
Base A substance that accepts hydrogen ions donated by an acid.
Boiling point The maximum temperature at which the liquid phase of a substance exists in equilibrium with its vapor phase. Above the boiling point, a liquid vaporizes completely. At its boiling point, the vapor pressure of a liquid is equal to the atmospheric pressure on it.
Carbon black An amorphous form of carbon.
Carcinogen Capable of causing cancer.
CAS number (CAS #) Chemical Abstract Service Registry number. This chemical identification number, in the format XXX-XX-X, is assigned by the American Chemical Society.
Catalyst A substance that speeds up (catalyzes) a chemical reaction between other substances without itself being chemically changed or consumed. Catalysts are widely used in the chemical industry. For example, an iron/aluminum catalyst is used to synthesize ammonia and a platinum catalyst is used to manufacture nitric acid. Compare with Initiator.
Catalyze To act as a catalyst.
Cation An atom or group of atoms having a positive net charge..
Caustic Strongly basic, with high pH. Very corrosive.
Cellulose A carbohydrate polymer that is the abundant cellular matrix found in all plant tissues. Cellulose is a complex polysaccharide.
Chronic Of long duration, or frequently recurring. Chronic health effects become apparent and/or continue for some time after exposure to hazardous chemicals.
Combustible Having a flash point above 143° F (62°C). Substances are considered combustible unless they are stated to be non-combustible.
Combustion Also burning. A chemical reaction between oxygen and another element or compound that is rapid and exothermic enough to generate heat and light.
Compound The combination of two or more elements into a distinct chemical material.
Concentration The amount of any substance present in a specified weight or volume of a mixture. concentrations usually relate to the amount of a substance mixed in air or water.
Condensation A reaction in which two molecules combine to form a larger molecule as a small molecule is split out. The condensation polymerization of amino acids into proteins occurs with the splitting out of water. Also, the change of water or other substances from vapor to liquid phase.
Contaminant The presence of a foreign and perhaps deleterious material in an otherwise pure material. Often synonymous with pollutant. In small quantities, may raise the rates of normal chemical reactions very rapidly, sometimes causing harmful effects.
Copolymer Or polyblend. A polymer generated when two or more different monomers join to form a macromolecule. The copolymerization process is often employed to produce elastomers with very specific physical properties.
Corrosive Having the quality of eating away or consuming by chemical action.
Covalent bond A chemical bond in which atoms of either like or unlike elements link by sharing electrons.
Cryogenic Matter at extremely low temperatures, usually approaching absolute zero (obtainable only by employing the liquefied gases hydrogen, helium, oxygen, and nitrogen).
Deflagration Rapid, sharp combustion with sudden evolution of flame.
Delayed A hazard category that includes carcinogens and other hazardous chemicals that adversely affect a target organ. Such effects generally result from long-term exposure and are of long duration.
Deliquescent The property of becoming liquid by absorbing moisture from the air.
Denature The addition of a toxic material such as benzene or methyl alcohol (a denaturant) to ethyl alcohol to inhibit or prevent its use for human consumption.
Density The ratio of weight to volume of any substance
Detergent A natural or synthetic agent that suspends emulsified oils, greases, and fats in solution and, by doing this, acts as a cleaning agent. Examples of detergents include soaps and various alcohols, sulfonated organics like dodecylbenzene, and various alkylates.
Detonation The very rapid decomposition of an explosive material, which produces a rapidly-propagating, high-pressure wave traveling at supersonic speeds.
Dew point The temperature at which air is saturated with water.
Dispersion The movement of molecules or finely divided particles through a gaseous or liquid medium. For example, the distribution of a toxic chemical cloud in the atmosphere.
Distillation The process of separating a mixture of materials by heating and then condensing the resulting vapors. The separation is made possible by the inherent differences in boiling point among the individual mixture components (each can be distilled out of the mixture at a particular temperature).
Efflorescent Tending to lose moisture to the air as shown by the formation of a powder on the surface.
Elastomer Any of a group of rubber-like polymers that have essentially the same properties as natural rubbers.
Electrolyte In a battery, the material that acts as a conductor of electric current between the dissimilar metal electrodes. These are ionically-bonded, inorganic salts that form ions in solution and thus increase electrical conductivity.
Electrons Negatively-charged elementary particles that have a very small mass. Electrons are components of all atoms; they are readily lost or gained by atoms. (See Ion.) The transfer and sharing (redistribution) of electrons among atoms is the basis of chemical change.
Electrophile A chemical reactant that tends to react at centers of negative charge.
Electroplating For corrosion protection or decorative purposes, an electrodeposition process that coats a surface with a thin film of metal (or plastic), by creating an electrolytic cell in which metal atoms are deposited on the cathode and the anode acts as the reservoir of ions in solution.
Emulsification Generally, either the dispersion of oil particles in water or water in oil. The emulsification process is relatively permanent, and may proceed with the help of an emulsification agent.
Endothermic A chemical reaction that must absorb heat from its surroundings in order to proceed. Contrast with exothermic, in which heat is produced by the forward reaction.
Enzyme Any of a number of complex proteins that act in extremely specific chemical reactions to accelerate reactions or catalyze a specific reaction. The rates of reaction are often many orders of magnitude faster than the rates for the same reaction at standard temperature and pressure conditions. All metabolic processes in living organisms are governed by enzymes.
EPA U. S. Environmental Protection Agency.
Exothermic A term used to describe the generation of heat from a chemical reaction. Contrast with endothermic, in which heat is taken in from the surroundings.
Explosion A chemical or physical process in which the rate at which energy is being generated exceeds its ability to escape to its surrounding environment. The hazards of an explosion can include a shock wave, especially near the point of explosion, and projectiles generated by the shock wave.
Explosive A material synthesized or mixed deliberately to allow the very rapid release of chemical energy. Also, a chemical substance that is intrinsically unstable and liable to detonate under conditions that might reasonably be encountered.
Extremely Hazardous Substances EHS) EHS chemicals have been identified by the U.S. Environmental Protection Agency as particular toxic threats. They are listed under EPCRA in the appendices to 40 CFR § 355, Emergency Planning and Notification.
Fermentation An energy-yielding reaction carried out in an anaerobic environment (without oxygen), catalyzed by enzymes (biochemical catalysts) and involving the decomposition of carbohydrates (sugars and starch) to form alcohols, carboxylic acids, and carbon dioxide.
Fire hazard A hazard category that includes chemicals described as flammable, combustible liquid, pyrophoric, or oxidizers
Flammability A substance's tendency to ignite or take flame. Flammability is closely related to the volatility of a substance (and is not its relative ability to burn in the presence of oxygen with the evolution of heat).
Flammability limits Or explosive limits. The lower flammability limit is the lowest concentration of a vapor in air that catches fire when exposed to a source of ignition. The upper flammability limit is the highest concentration of the vapor in air that catches fire when exposed to a source of ignition. The flash point and lower and upper flammability limits of a substance are often used as measures of its flammability hazard in a given situation.
Flammable Having a flash point lower than 143° F (62°C) and greater than 100°F (38°C).
Flash point The lowest temperature to which a substance must be heated before the vapor-air mixture above it will be ignited by a free flame in the open air.
Fluorescence A luminescent (light-emitting) quality of an organic dye or inorganic substance. In fluorescent substances, light emission continues only as long as the excitation energy lasts. Differs from phosphorescence, in which light emission lasts for many seconds or even hours after excitation occurs. Also, in fluorescence, excitation generally is immediately followed by emission of energy, while in phosphorescence, energy emission may be delayed.
Free radical A molecule in which a portion is highly reactive because chemical bonds have been ruptured by thermal radiation from combustion or ionizing radiation. Conceptually, a free radical molecule contains sites with an unpaired electron available to attack other molecules. Free radicals often are involved in chain reaction-type mechanisms, such as combustion processes and the industrial processes used to make polymers.
Fuming Describes the release of fumes by highly active inorganic liquids such as nitric acid; the fumes form a noxious vapor cloud. Nitric, sulfuric, and hydrofluoric acids and similar acids produce very dangerous levels of fumes when they are in their pure state. The presence of water somewhat reduces the production of fumes.
Glacial A term used for certain acids, such as acetic or phosphoric acid, indicating a very pure form of the acid with a freezing point just below room temperature.
Hazardous chemical Any chemical that is a physical or health hazard
Hazardous material Any substance or material in a quantity or form that may be harmful to humans, animals, crops, water systems, or other elements of the environment, if accidentally released. Hazardous materials include: explosives, gases (compressed, liquefied, or dissolved), flammable and combustible liquids, flammable solids or substances, oxidizing substances, poisonous and infectious substances, radioactive materials, and corrosives.
Heat of combustion The heat generated when a substance is completely oxidized to product gases such as sulfur dioxide, carbon dioxide, and nitrogen dioxide.
Heat of crystallization The heat evolved when a crystal is formed from a saturated solution of a substance.
Heat of dilution The heat evolved when a solution is diluted from one concentration to a lower concentration.
Heat of hydration The heat evolved when ions in solution are hydrated. That is, the heat produced when the hydrate of a substance is formed..
Heat of reaction The heat evolved during a chemical reaction.
Hemoglobin An iron-containing protein molecule. Hemoglobin is a characteristic component of red blood cells, which carries oxygen to the tissues of the body.
Highly flammable Designation applying to (a) substances with flash points below 100°F, and (b) mixtures that include substances with flash points below 100°F. Materials designated as highly flammable include pyrophoric solids and substances that present an exceptional flammability hazard, in that they may suddenly and dangerously increase the intensity of a fire.
Humidity The ratio of the amount of water vapor being held in the air at any given temperature to the maximum that can be held in the air at that temperature.
Hydration Or solvation. The association of molecules of water with inorganic substances, usually salts, to form hydrates. Also refers to the strong affinity of water molecules for ions in aqueous solution.
Hydrocarbon An organic compound containing only hydrogen and carbon.
Hydrogen ion A hydrogen atom that has lost its single electron and consequently has a positive charge. Water (H2O) can be thought of as a combination of hydrogen ion (H+) and hydroxide ion (OH-).
Hydrolysis A chemical reaction in which a bond is broken by the agency of water. A hydrogen ion and hydroxide ion from the water become independently attached to the two atoms previously linked.
Hydrolyze To break down by means of reaction with water.
Hydrophilic Lit. "Water-loving." Refers to substances that attract and retain water, and to wettable solids whose surfaces readily attract water.
Hydrophobic Lit. "Water hating." Refers to substances that repel water and are not easily wetted or emulsified (fats, waxes, oils, metal powders, and many inorganic compounds).
Hydroxide ion An ion with an overall negative charge, composed of a single oxygen and a single hydrogen atom. Water (H2O) can be thought of as a combination of hydrogen ion (H+) and hydroxide ion (OH-).
Hygroscopic Capable of readily absorbing moisture from the air, so as to swell up, contract in length, or change form or consistency.
Hypergolic Igniting spontaneously on contact with another substance, which is typically an oxidizing agent.
IDLH The Immediately Dangerous to Life or Health (IDLH) value represents the maximum airborne concentration of a chemical to which a healthy adult worker can be exposed and escape without suffering irreversible health effects or symptoms that impair escape (ranging from runny eyes that temporarily impair eyesight to a coma). IDLH values are derived primarily from mammalian toxicity studies.
Immediate (acute) hazard A hazard category that includes highly toxic, toxic, irritant, sensitizer, corrosive (as defined by 29 CFR § 1910.1200), and other hazardous chemicals that cause an adverse effect to a target organ. Such effects usually develop rapidly, result from short-term exposure, and are of short duration.
Immiscible Substances of the same phase (liquid or solid) that cannot be mixed in any proportion with one another..
Impurity Usually, a very small amount of a foreign or extraneous substance that naturally or by accident exists in a substance. Many cases have been documented in which unintended impurities caused severe consequences during a chemical reaction process (often, processes such as polymerization reactions in which a small amount of impurity acted as a catalyst to initiate a runaway reaction)..
Inert Non-reactive in nature. Refers to substances that have little or no chemical activity or affinity. Some of the best-known inert substances are the noble gases such as helium and neon.
Inert gas A vapor or gas containing sufficient oxygen to support combustion. Used to control cargo tank atmospheres and to prevent the formation of flammable mixtures.
Ingestion A route of chemical exposure in which a toxic material is brought into the bloodstream by entering the digestive tract.
Inhalation A route of chemical exposure in which a toxic material is brought into the bloodstream as particles or volatile compounds breathed into the lungs and nasal passages.
Inhibitor Substance that acts to retard or slow the rate of a chemical reaction. Probably the most important inhibitors are the antioxidants, which slow the oxidation of many types of materials such as rubber and food products..
Initiator A substance that, because of its unusual chemical activity, may induce chemical reaction in other substances. Reactions such as polymerization, oxidation (formation of peroxides), and detonation (rapid combustion) are aided by initiators.
Inorganic Compounds that do not contain the element carbon, as well as the following carbon-containing compounds: the carbon oxides, the carbides, carbon disulfide, phosgene, cyanides of metals, and carbonyl sulfide.
Ion An atom or group of atoms that has an overall non-zero electric charge (which may be either negative or positive).
Irradiation The impingement of radiation of a specific wavelength on a substance to initiate a chemical change.
Isomer Compounds sharing the same molecular weight and molecular formula, but having different chemical structures. The difference in structure often causes differences in chemical and physical properties such as boiling point, melting point, and water solubility. Property differences among isomers produce differences in their reactivity and toxicity.
Isotope Elements that are otherwise identical but that have different weights because they have different numbers of neutrons in their nuclei. The simplest example is the isotopes of hydrogen, including H1, normal hydrogen, and H2, or deuterium, which has an additional neutron.
Lachrymator Irritating to the eyes in a way that induces tears. Tear gas is a lachrymator.
Lacquer A fast-drying, organic coating material.
Lignin An amorphous organic polymer that helps bind cellulose fibers together in plant tissue.
Liquor Any one or more compound mixtures in aqueous phase.
Litmus A substance or material that, on contact with another substance, indicates that substance's pH or hydrogen ion concentration. Examples include litmus paper and pH indicator solutions.
Lower explosive limit (LEL) Or lower flammability limit. The lowest concentration of a flammable vapor in air at which explosion or combustion can occur. See also Upper Explosive Limit (UEL).
Luminescence The phenomenon in which a substance that has absorbed radiant excitation energy emits radiation on return from some excitation state to its ground state energy.
Material Safety Data Sheet (MSDS) A worksheet containing information about a hazardous chemical in the workplace. MSDSs are submitted by facility owner/operators to meet the chemical inventory reporting requirements of EPCRA. Under 29 CFR 1910.1200, facilities must develop an MSDS for each hazardous chemical present on site.
Melting point Also freezing point. The temperature at which the solid and liquid phases of a substance exist in equilibrium. Depends on chemical composition and applied pressure.
Mineral The inorganic constituents of the earth's crust. Most minerals have a definite internal structure and chemical composition.
Miscible The degree to which one substance can be mixed with another (usually, related to the degree to which a solute may mix in a particular solvent). Some materials, such as gases generally as well as ethyl alcohol in water, are completely miscible with one another in any proportion.
Mist Extremely small liquid particles which are suspended in a gas phase.
Mixture A uniform or nonuniform blend of two or more substances. Examples include blood, milk, petroleum products, and alloys.
Molar A concentration expressed as the number of gram molecular weights of a solute mixed into one liter of solvent, usually water. A 1-molar solution of sodium hydroxide contains 40 grams of sodium hydroxide in each liter of water.
Molecular Weight The sum of the weights of all the atoms in a molecule.
Molecule A chemical entity composed of one or more elements in the form of atoms.
Monomer One of the molecules that link together to make a polymer. For example, the monomer of natural rubber is isoprene. Monomers may be naturally occurring or synthetic.
Mucous membranes those surfaces of the respiratory system lined with secretion like the nose , throat, windpipe and lungs.
Mutagen A chemical or radiation source that alters an organism's DNA, affecting transmission of inherited characteristics from one generation to the next.
National Institute for Occupational Safety and Health (NIOSH The Federal agency responsible for conducting research and making recommendations for the prevention of work-related disease and injury. NIOSH is part of the Centers for Disease Control and Prevention (CDC).
National Response Center (NRC) The central Federal clearinghouse for information on hazardous chemical spills and other oil or hazardous substance releases. Responsible parties should contact the NRC in order to fulfill reporting requirements for spills of oil and hazardous substances (hotline: 1-800-424-8802) NRC is the OSRO.
National Response Team (NRT) A planning, policy, and coordinating body consisting of representatives from 16 federal agencies with interest and expertise in aspects of emergency response to pollution incidents. The NRT provides national level policy guidance prior to an incident and can provide assistance during an incident.
Neutralization/Neutralize The reaction between an acid and base to form a salt and water. Neutralization is often rapid, vigorous, and exothermic (heat-producing).
Noble gases A group of six elements (helium, neon, argon, krypton, xenon, and radon) exhibiting little or no chemical reactivity. Non-combustible Non-reactive with air, even at very high temperatures.
Nonoxidizing Completely or nearly lacking the ability to oxidize (to transfer oxygen to other groups or lose electrons to other groups).
NOx The oxides of nitrogen, taken as a group. Nitrogen forms several distinct compounds with oxygen; some of these compounds convert back and forth readily under ordinary conditions.
Nucleophile A chemical reactant that tends to react at centers of positive charge.
Occupational Safety and Health Administration (OSHA). Federal agency within the U. S. Department of Labor with the responsibility of ensuring worker safety and health.
Olefin An alkene.
Organic Generally, compounds that contain the element carbon, except for some carbon-containing compounds that are considered to be inorganic (carbon oxides, carbides, carbon disulfide, phosgene, the cyanides of the metals, and carbonyl sulfide).
Oxidation A chemical reaction in which oxygen bonds to an element or compound. By extension, a reaction in which one element or compound rises to a higher oxidation state while another drops to a lower oxidation state (the term is used in this sense even when no oxygen whatever is present).
Oxidation number An arbitrary number assigned to an atom in a compound. Oxidation increases the total oxidation number of the atoms in a compound; reduction reduces it.
Oxidizing agent A material capable of bringing about oxidation (the loss of electrons) in other materials, while it is itself reduced (gains electrons).
Peroxidizable Apt to react spontaneously with oxygen at room temperature, to form peroxides and other products. Most such autooxidations are accelerated by light or by trace impurities. Because many peroxides are explosive, peroxidizable compounds are especially hazardous. Ethers and aldehydes are particularly peroxidizable.
pH A number indicating the acidity or alkalinity of an aqueous solution, defined as the negative logarithm of the hydrogen ion concentration in moles per liter. At room temperature, a solution having a pH of 7 is neutral (neither acidic nor basic). Solutions with pHs greater than 7 are basic (alkaline); solutions with pHs below 7 are acidic.
Pitting a form of corrosion as little holes on the steel surface.
Polymer The product of polymerization. Proteins, starches, cellulose and natural rubber are naturally occurring polymers; polystyrene, nylon, Teflon, and synthetic rubber are synthetic polymers.
Polymerizable Capable of undergoing polymerization, an energy-releasing self-reaction. The products of polymerization reactions are generally less reactive than the starting materials.
Polymerization A chemical reaction in which a large number of smaller molecules (monomer units) join together by chemically linking into chains or networks (polymers). Energy is released during polymerization reactions
ppb Parts per billion. Units used to express the concentration of a gas or vapor in air (as molecules of chemical per billion molecules of air).
ppm Parts per million. Units used to express the concentration of a gas or vapor in air (as molecules of chemical per million molecules of air).
Prill Small spherical or cylindrical pellets used in the fertilizer and explosive industry, because they are convenient to handle. An example is ammonium nitrate prills, which are often coated with a wax because this salt has a tendency to cake when hydrated.
Pyrophoric Any substance that ignites in the presence of air at or below ambient temperatures. Many pyrophoric materials react with moisture in the air to generate flammable hydrogen gas and enough heat to ignite the hydrogen. These are extremely dangerous fire hazards that are generally stored under an inert atmosphere or in a solvent like ether or kerosene that excludes air.
Pyrotechnics The manufacture of fireworks, signal flares, and so on, involving the mixture of different chemicals to achieve various visual and auditory effects. Chemicals used in pyrotechnics include many explosive inorganic compounds such as potassium nitrate, metal perchlorates, dichromate, powdered metals, and phosphorus.
Radiation Electromagnetic energy or light, depending on the wavelength, which imparts energy to molecules and atoms. Radiation absorption causes ionization and bond-breaking.
Radical In inorganic chemistry, refers to an aqueous, dissociated ionized group. In organic chemistry, refers to an uncharged alkyl, aryl, or other group that acts as a fragmented, highly reactive, short-lived substance. Free radical generation is a very important reaction that can initiate polymerization and other kinds of reactions.
Rapid reaction A reaction in which chemical change becomes evident within minutes to hours after the mixing of incompatible chemicals. That evidence can be dramatic change such as fire or explosion, or more subtle effects, such as chemical heat production, evolution of gases, or deposition/disappearance of solids.
Rare Can refer either to the noble gases (helium, neon, and argon), the rare-earth elements (or lanthanide series, starting with lantanum), or rare metals such as gold, silver, cadmium, and platinum.
Reactive A hazard category that includes chemicals described as unstable, reactive, organic peroxide, or water-reactive
Reactive group Reactive groups are categories of chemicals that react in similar ways because they are similar in their chemical structure. For purposes of predicting reactivity between mixed chemicals, each substance in the Chemical Library has been assigned to one or more reactive groups, based on the known chemistry of that substance
Reactive hazard Some chemicals pose special or acute reactivity-related hazards that are intrinsic to those chemicals because of their structures and known physical characteristics. special reactive hazards include a chemical's tendency to be flammable, explosive (either by itself or when mixed with other materials), peroxidizable, polymerizable, air- and or water- reactive, radioactive, or a strong oxidizer or reducer.
Reactivity The tendency of a substance to take part in chemical change. The reactivity of most kinds of substances depends on the temperature and pressure of the surroundings, and on the identity and physical form of other chemicals with which a given substance is in contact. In contrast, innately reactive substances include those that react rapidly with water, air, and other common components of the environment under ordinary conditions, as well as substances that self-react (decompose or polymerize) under ordinary conditions.
Reagent Any chemical substance used in chemical analysis.
Redox A contraction for "oxidation-reduction." Redox reactions, in which electrons are transferred from a reducing agent to an oxidizing agent, are a major category of chemical change.
Reducing agent A substance that can bring about reduction (gaining of electrons) in other substances, while it is itself oxidized (loses electrons).
Reduction A reaction in which either oxygen is removed from a substance or, in a more general sense, one or more electrons is accepted from another substance. (Can also mean a process in metallurgy by which materials are separated into their wanted and unwanted components from an ore body.) Contrast with Oxidation.
Resins Naturally-occurring "essential oils" that are water-insoluble and extracted from natural sources, such as trees and shrubs. Also, synthetic polymers such as polystyrene or polyethylene, even though such materials are not complex mixtures of compounds like other resins, but instead are long, complex polymers.
Risk analysis A systematic method of assessing the damage that could be caused to a community by a hazardous substance release.
Salt An ionic compound derived from the combination of cations (positively-charged ions) with anions (negatively-charged ions). Sodium chloride (common table salt) is an example.
Saturated Refers to organic compounds that contain the maximum possible number of hydrogen atoms per carbon atom. Also used to describe a solution of a solute that is at its solubility limit in a given solvent system at a specified temperature.
Skin absorption Chemical exposure through the skin. Because the skin does not act as a reliable barrier to hazardous chemicals, it can be a route of acute poisoning. Compounds such as dimethyl sulfoxide are known to be directly absorbed into the bloodstream through the skin.
Sludge A thick or viscous mixture of solids in aqueous solution, such as sewage sludge.
Slurry A dilute mixture or suspension of solid particles in water, such as clay, fiber, or metal powders.
Soda ash Sodium carbonate.
Solute/Solvent A solute is a gas, liquid, or solid substance that is uniformly dispersed in a liquid solvent substance, forming a solution. The solvent molecules act to break the solute molecules' attraction for one another, and also the solvent's natural structure. For instance, water is a highly-structured substance, in the absence of any solutes.
Solution A molecularly uniform mixture of one or more solutes in a solvent. Sometimes, one or more of the solutes are ionized in solution.
Specific gravity The ratio of the density of a substance at a given temperature to the density of water at the same temperature. A substance with a specific gravity greater than 1.0 will sink rather than float in water.
Spectroscopy The qualitative and quantitative analysis of emitted and absorbed energy, done by subjecting a substance to electromagnetic energy. The wavelength of this excitation energy can vary from gamma and x-ray to radio frequency.
Stabilizer Any substance that, when added to another, acts to prevent or retard chemical or physical change in the latter. Examples include antioxidants, inhibitors, and emulsifying agents.
Starch A carbohydrate or polysaccharide polymer composed of amylose and amylpectin. Starch occurs in plant tissues such as potatoes, tapioca, and rice, and is used as a thickening agent in foods.
Static accumulator A liquid with an electrical continuity of less than 50 pico Siemens / metre , so that it is capable of retaining a significant electrostatic charge.
Strong oxidizing agent Oxidizing agents gain electrons from other substances and are themselves thereby chemically reduced. Strong oxidizing agents accept electrons particularly readily from many other substances. The ensuing redox reactions may be vigorous or violent and may release new substances that may take part in further additional reactions. Keep strong oxidizing agents well separated from strong reducing agents.
Strong reducing agent Reducing agents give up electrons to other substances, and are themselves thereby oxidized. Strong reducing agents donate electrons particularly readily to many other substances. The ensuing redox reactions may be vigorous or violent and may generate new substances that take part in further additional reactions. Keep strong reducing agents well away from strong oxidizing agents.
Sublime The change of a substance from the solid state to the vapor state, without passing through the liquid intermediate state. Substances that sublime include solid carbon dioxide, sulfur, camphor, and naphthalene.
Surfactant A substance that reduces surface tension of liquids. Nearly synonymous with detergent (which reduces the surface tension of water), wetting agent, and emulsifier.
Suspension A uniformly-dispersed mixture of fine particles in a liquid.
Synonyms A single chemical may have many names. The synonyms by which a chemical is named can include common names in different languages, trade names, and other names.
Technical grade Term applied to substances that are unrefined, impure, and/or less than 100% pure grade.
Thermoplastic Any substance that is solid or semisolid at room temperature, but becomes liquid when heated. Thermoplastic substances can be molded or shaped and hold their shape until heated. Examples include butter, waxes, and certain polymers.
Threat zone A threat zone encloses the area around the location of a hazardous chemical release, within which concentrations of the chemical could reach or exceed a specified LOC (level of concern).
TLV threshold limit value. Allowed exposure dose. STEL: short term exposure limit. TWA: time weighted average (longer period exposure limit).
UN/NA number Or UN number. A chemical identification number, assigned under a numbering system developed by the U.S. Department of Transportation. This system has since become the United Nations standard system for classifying hazardous materials.
Unsaturated Refers to organic compounds that contain fewer than the maximum possible number of hydrogen atoms per carbon atom.
Upper Explosive Limit (UEL) The highest concentration of a flammable vapor in air at which explosion or combustion can occur. Above this concentration, the vapor-air mixture is too rich to combust. See also Lower explosive limit (LEL).
UV Abbreviation for Ultraviolet radiation.
Vapor density The ratio of the density of a gas to the density of air at the same temperature. A gas with a vapor density greater than 1.0 is heavier than air and will sink in the atmosphere.
Vapor pressure In a closed system containing an evaporating liquid and its vapor, the equilibrium at which the number of vapor molecules reentering the liquid equals the number going from the liquid to the vapor phase. Vapor pressure is commonly expressed in pressure units of either millimeters of mercury (mm Hg), pounds per square inch (psi), or atmospheres (atm).
Viscosity The tendency of a liquid substance to resist movement or flow due to an external force applied to it.
Volatile/Volatility Refers to the ease with which a substance goes from liquid or solid phase to the vapor phase (via evaporation or sublimation). The volatility of a given substance increases with temperature.
Water of crystallization Water chemically combined within a crystalline substance.
Water-reactive Substances that may react rapidly or violently with liquid water and steam, typically forming toxic and/or flammable products and heat.
Water solubility Mixing of gas, liquid, or solid materials in water. The highest amount of a particular material that can be mixed in water is its water solubility. Water solubility ranges shown in Chemical Library records are as follows: Water insoluble: <1 mg/ml; Slightly water soluble: 1-10mg/ml; Water soluble: >10 mg/ml.
Wettable powder A solid material whose surface is hydrophilic, and therefore attracts water.
CAPT AJIT VADAKAYIL
-------CAPT AJIT VADAKAYIL