PREPARATIONS 183 When an aqueous solution of benzenediazonium chloride is added to a cold concentrated solution of potassium hydroxide, the unstable potassium diazo-tate, C 6 H 6 NiNOK, is formed, and this when heated with alkali to 130° changes to the isomeric but far more stable potassium isodiazotate: it is probable that these compounds have the structures (A) and (B) respectively. C 6 H 6 N C,H S N (A) I] —> I (B) KON NOK In preparing an aqueous solution of a diazonium salt, such as benzene-diazonium chloride, it is usual to dissolve the amine in a slight excess (about 2-2 molecular equivalents) of dilute hydrochloric acid (or alterna-tively to dissolve the crystalline amine hydrochloride in 1*2 equivalents of the acid) and then add an aqueous solution of a metallic nitrite. Nitrous acid is thus generated in situ, and reacts with the amine salt to give the diazonium compound. For a successful preparation of an aqueous solution of the diazonium salt, however, two conditions must
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