Certain combinations of chemicals are explosive, poisonous, or extremely hazardous in some way. Most chemicals are listed on the Material Safety Data Sheet (MSDS) in the following manner:

Chemicals which are listed in different chemical classes must NEVER be stored together. The following list is a sample of some of the more hazardous combinations.

Sodium (Na)

Water, oxidizers, acids, carbon dioxide, carbon tetrachloride, halogenated hydrocarbons, heavy metal oxides, methyl chloride, chloroform, haloids, nitrous oxide, tetrachloroethane, trichloroethylene

Calcium (Ca)

Water, acids, oxidizers, carbonates, dinitrogen tetroxide, halogenated hydrocarbons, lead chloride, halogens, alkaline hydroxides, oxygen, silicon, sulfur, chlorine, flourine, chlorine trifluoride

Potassium (K)

Water, oxidizers, organic material, acetylene

Acetic Acid (H₃C-COOH)

Chromic acid, phosphorus trichloride, perchloric acid, permanganates, ethylen diamine, ethyleneimine, phosphorus isocyanate, acetaldehyde, ammonia, ammonium nitrate, chlorosulfonic acid, xylene

Acetone (H₃C-CO-CH₃)

Concentrated Sulfuric Acid (H₂SO₄), Nitric Acid (HNO₃) Chloroform, strong acids, aliphatic amines, hcromic anhydride, chromyl chloride, hexachloromelamine, hydrogen peroxide, nitrosyl chloride, nitrosyl perchlorate, permonsulfuric acid, potassium tert-butoxide

Acetylene (C₂H₂)

Oxidizers, copper & copper salts, mercury & mercury salts, silver & silver salts, brass, bromine, cesium hydride, chlorine, cobalt, cuprous acetylise, fluorine, iodine, mercuric nitrate, nitric acid, potassium, rubidium hydride, trifluoromethyl hypofluorite, sodium hydroxide

Ammonia, Anhydrous (NH₃)

Oxidizers, acids, halogens, mercury oxide, silver oxide, trioxygen difluoride, selenium difluoride dioxide, mercury, iodine, hypochlorites, amides, isocyanates, alkylen oxides, aldehydes, trimethylammonium amide, 1-chloro-2,4,dinitrobenzene, o-chloronitrobenzene, platinum, boron halides, chlroine, bromine, chlroine bleach, organic anhydrides, vinyl acetate, epichlorohydrin

§    Attacks copper, brass, bronze, aluminum, steel and their alloys

§    Attacks some coatings, plastics and rubber

Ammonium Nitrate (NH₃NO₃)

Reducing agents, combustibles, organic materials, finely divided metals

Chlorate of Potash

Reducing agents, combustibles, ammonia gas, ammonium salt, organic matter, ammonium chloride, hydrogen iodide, organic acids, sulfuric acid, metallic powder, organic solids

Chlorate of Soda

Reducing agents, ammonia salts, oil, nitrobenzene, powdered metals, carbon, metal sulfides, sugar

Chromic Acid (CrCO₃)

Acetic acid, acetic anhydride, diethyl ether, dimethyl formamide, ethanol, methanol, camphor, potassium ferricyanide, organics, combustibles, turpentine, acetone, pyridine, anthracene, chromous sulfide, hydrogen sulfide, naphthalene, glycerol
Attacks metal in the presence of moisture

Hydrogen Peroxide (H₂O₂)

Potassium permanganate, organics, readily oxidizable materials, reducing agents, combustibles, iron, copper, brass, bronze, chromium, zinc, lead, manganese, silver and other catalytic metals and their salts

Hydrocarbons

Bromic Acid (HNO₃)
Sodium Peroxide (Na₂O₂)

Mercury (Hg)

Acetylene, acetylene products, ammonia gases, boron phosphodiiodide, chlorine, chlorine dioxide, methyl azide, copper and copper alloys

Nitric Acid (HNO₃)

Potassium permanganate, reducing agents, combustible materials, acrylates, aliphatic amines, alcohols, aldehydes, alkanolamines, alkylene oxides, cresols, cyanides, glycols, isocyanates, ketones, phenols, sulfuric acid, strong oxidizers, terpenes

Perchloric Acid (HClO₄)

Reducing agents, combustible materials, acetic acid, alcohol, glycol, hypophosphites, ketones, metal powders, strong acids, sulfoxides

Potassium Permanganate (KMnO₄)

Sulfuric acid, acetic anhydride, anhydrous ammonia, hydrogen peroxide, glycerol, hydroxylamine, organic matter, powdered sulfur, nitric acid

Sodium Peroxide (Na₂O₂)

Water; aqueous solution incompatible with: acids, organic anhydrides, isocyanates, alkylene oxides, epichlorohydrine, aldehydes, alcohols, glycols, phenols, cresols, cappolactam solution, reducing agents, combustible materials, organic substances, acids, metal powders

Sulfuric Acid (H₂SO₄)

Reducing agents, organic and combustible substances and bases, non-oxidizing mineral acids, organic acids, bases, acrylates, aldehydes, alcohols, alkylene oxides, ammonia, aliphatic amines, alkanolamines, aromatic amines, amides, chlorates