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Chemical Compatibility Guidelines

Separate and store chemicals by compatibility group.

Segregate incompatible chemicals

Perhaps the single most important rule of chemical storage is to segregate incompatible chemicals to prevent accidental mixing which could cause fire, explosion, or toxic gases.

Hazardous chemical reactions can occur from improper storage when incompatible materials mix because of:

  • Accidental breakage
  • Container failure
  • Fires and earthquakes
  • Mixing of gases or vapors from poorly closed containers
  • Mistakenly storing incompatibles together because of improperly labeled containers

Chemical compatibility groups

Store chemical groups below separately from one another, either in separate cabinets or in appropriate tubs or secondary containers. Clearly and legibly label each container and storage location to indicate its compatibility group.

  • Flammable liquids (flashpoint <100°F) — Examples: All alcohols, acetone, acetaldehyde, acetonitrile, amyl acetate, benzene, cyclohexane, dimethyldichlorosilane, dioxane, diethyl ether, ethyl acetate, histoclad, hexane, hydrazine, methyl butane, picolene, piperidine, pyridine, some scintillation liquids, all silanes, tetrahydrofuran, toluene, triethylamine, and xylene
  • Compressed gases — Examples: Oxygen, nitrogen, hydrogen, arsine, and acetylene
    • Store securely mounted.
    • Segregate oxygen from flammable gases.
    • Store acutely toxic and toxic gases in gas cabinets or fume hoods.
  • Volatile poisons — Examples: Poisons, toxics, and carcinogens, such as carbon tetrachloride, chloroform, dimethylformamide, dimethyl sulfate, formamide, formaldehyde, halothane, mercaptoethanol, methylene chloride, and phenol
    • Store in a ventilated cabinet.
    • May be stored with flammable liquids if bases are not present.
  • Acids  — Important: Segregate acids from chemicals which could generate toxic or flammable gases upon contact (e.g., cyanide salts, metal sulfides, calcium carbide) and reactive metals (e.g., sodium, potassium, magnesium).
    • Store in a ventilated corrosive storage cabinet if possible.
      • Corrosive to living tissue.
      • Corrosive to metal surfaces.
    • Store in non-corrosive secondary container (e.g., appropriate sized plastic tub).
    • Avoid contact with bases!
    • Mineral acids:
      • Oxidizing – Examples: Sulfuric, nitric, chromic, perchloric
        • Store separately from organic acids.
        • Highly reactive with most substances, these acids must be double contained (i.e., the primary container must be kept inside a non-corrosive canister, tray, or tub).
        • Perchloric acid presents special hazards. Carefully isolate it from acetic anhydride, bismuth and its alloys, alcohol, paper, wood, oil, ether, grease, and sulfuric acid.
        • Take special precautions to keep perchloric acid away from acetic acid.
      • Non-oxidizing – Examples: Hydrochloric, hydrofluoric, phosphoric, hydroiodic
        • Hydrofluoric acid (HF) is particularly hazardous and must be handled carefully. HF is a high hazard chemical. UCSD researchers working with HF must follow an approved hazard control plan obtained through the Chemical Hazard Use Application (CHUA).
    • Organic acids – Examples: Acetic, butyric, formic, propionic
      • Store separately from oxidizing mineral acids.
      • Corrosive to metal surfaces.
      • Store in a ventilated corrosive storage cabinet if possible.
      • Can be stored with organic solvents unless otherwise noted on the Safety Data Sheet.
      • Take special precautions to keep acetic acid away from perchloric acid.
  • Liquid bases — Examples: Sodium hydroxide, ammonium hydroxide, calcium hydroxide, glutaraldehyde
    • Store in tubs or trays in a normal cabinet.
    • Avoid contact with acids.
    • Liquid bases may be stored with flammables in the flammable cabinet if volatile poisons are not present.
  • Liquid oxidizers — Examples: Ammonium persulfate, hydrogen peroxide
    • Store in a ventilated corrosive storage cabinet.
    • Oxidizing liquids react with nearly everything. They may potentially cause explosions, and must be double contained (i.e., the primary container must be kept inside a canister, tray, or tub).
  • Non-volatile liquid poisons — Examples: Acrylamide solutions, coomassie blue stain, diethylpyrocarbonate, diisopropyl fluorophosphate, uncured epoxy resins, ethidium bromide, triethanolamine
    Note: This group contains carcinogens and highly toxic chemicals.
    • Store in a normal cabinet, preventing contact with other materials.
    • May be stored with non-hazardous liquids, such as buffer or salt solutions.
    • Double contain quantities greater than one liter.
    • If you are storing carcinogens, see Chemical Carcinogen Overview for more detailed information.
  • Metal hydrides and pyrophorics (air or water reactive) — Examples: Sodium borohydride, calcium hydride, lithium aluminum hydride.
    • Most metal hydrides react violently with water.
    • Make sure a Type D fire extinguisher is available.
    • Store in a waterproof double container in a normal cabinet.
    • May be stored with dry solids.
  • Dry solids — Examples: All hazardous and non-hazardous powders, such as cyanogen bromide, ethylmaleimide, oxalic acid, potassium cyanide, and sodium cyanide
    • Store dry solids above liquids in a normal cabinet or on open shelves. It is particularly important to keep liquid poisons below cyanide- or sulfide-containing poisons (solids). A spill of aqueous liquid onto cyanide- or sulfide-containing poisons would cause a reaction that would release poisonous gas.
    • If properly double contained, dry solids can be stored with metal hydrides.
    • Solid picric acid or picric sulfonic acid may be stored with dry solids, but should be checked regularly for dryness. When completely dry, picric acid is explosive and may detonate upon shock or friction.

Read Chemical Storage and Inventory for more information.