Materials in this group are mostly nonflammable and non-combustible. Exceptions include the alcoholic solutions of sodium methylate (in which the solvent is flammable) and other mixtures that contain organic components. Also, ammonia, which is considered to be nonflammable, actually can burn (although it is difficult) and in confined spaces has exploded.

Compounds in this group neutralize acids exothermically to form salts plus water. When soluble in water they give solutions having a pH value between 7 and 12. Mixing these materials with water can generate troublesome amounts of heat as the base is dissolved or diluted. Bases react with certain metals (such as aluminum and zinc) to form oxides or hydroxides of the metal and generate gaseous hydrogen. 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. Bases are considered weak if they possess a pKa value less than 12 or a pH value between 7 and 12.

Ammonium hydroxide, disodium trioxosilicate, dithiazanine iodide, potassium cyanide solution, triethylamine.