Sulphazotinic Acid, H₆N₂S₄O₁₄

The potassium salt of Sulphazotinic Acid, H₆N₂S₄O₁₄, is obtained as in the preceding preparation by the action of sulphur dioxide on a solution of potassium nitrite, but in this case the solution is boiled. The salt consists of colourless, transparent, rhomboidal crystals, soluble in hot water, yielding an alkaline solution. Ammonia is evolved on heating the salt with soda-lime; concentrated acid liberates nitric oxide. The salt is decomposed by dilute acids with formation of sulphuric acid. On oxidation with lead dioxide or silver oxide at about 50° C. a solution of the salt becomes dark blue in colour, the potassium salt of dehydrosulphazotinic acid, K₄N₂S₄014, being formed:

K₅N₂HS₄O₁₄ + O = KOH + K₄N₂S₄O₁₄.