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salts of picric acid, or 2,4,6-trinitrophenol. Metal picrates are crystals ranging from yellow to red in color; Li and Na salts are moderately soluble in water, whereas salts of K and heavy metals, such as Pb, Cu, and Ca, are poorly soluble. Pi-crates are obtained by the action of metal hydroxides or carbonates on picric acid solutions, as well as by exchange reactions between barium or lithium picrates and the sulfates or nitrates of some metals, most often Pb.
Picrates are highly sensitive to mechanical effects and are readily inflammable and quick-burning explosives (the combustion rates for magnesium, potassium, and lead picrates at a pressure of 5 meganewtons per sq m, or 50 kilograms-force per sq cm, are 1.2, 3.5, and 21 cm sec, respectively). They have high thermal stability (particularly potassium and magnesium salts).
Organic bases are often isolated from mixtures and identified in picrate form. The term “picrates” is also used to designate complexes formed for aromatic hydrocarbons and picric acid.