Potassium azodisulfonate

Potassium azodisulfonate, 4663 Potassium 4-nitrobenzeneazosulfonate, 2175 Potassium /V-nitrosohydroxy lam inc-/V-sul foliate. 4662 Potassium sulfmdiimidate, 4664... 

A suspension of 130 g. of dry hydrazine sulfate In 600 g. of dry pyridine is prepared. Chlorosulfonic acid (300 g.) is added in portions from an addition funnel with stirring and cooling. Finally, the mixture is heated to 90-100°C on a water bath. It is then allowed to cool, and alcohol Is added with shaking. The crystalline mass that separates Is suction-filtered. For purification the pyridine salt so obtained is redissolved in a small amount of water, some alcohol is added, and the mixture is evaporated in a desiccator until copious crystallization is induced. The crystals are then suction-filtered. This pyridine salt, in the form of needles with a silken sheen, can be used for the preparation of potassium azodisulfonate. The compound is readily soluble in water and very slightly soluble in alcohol. For the preparation of the potassium hydrazinedisulfonate, the crystals need not be isolated. Thus, Instead of alcohol, 300 g. of ice and as much potassium hydroxide solution (d 1.39) as needed to make the solution barely alkaline are added to the impure mixture after coolii. The precipitated salt is suction-filtered and washed with cold water. The yield is about 200 g. 

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