High Purity Anhydrous Hydrazine

Methods heretofore known for the preparation of hydrazine in anhydrous condition were both tedious and uneconomic. It is the object of the present invention to provide a simple process for obtaining anhydrous hydrazine in high yield. 

The process of this invention is based upon the discovery that phthalyl hydrazides, sparingly soluble and relatively nonvolatile acids of high melting point, combine with hydrazine to form well-defined nonhydrated salts. 

The present invention, therefore, comprises a process for the isolation of anhydrous hydrazine which consists in dissociating an anhydrous phthalyl hydrazide salt of hydrazine, by distillation, preferably under reduced pressure, and collecting the hydrazine thus liberated. 

The phthalyl hydrazide salts of hydrazine may be prepared by various methods, e.g. by direct combination of a phthalyl hydrazide and hydrazine. 

An important feature of this invention consists in the preparation of anhydrous hydrazine by dissociating the anhydrous hydrazine salt of phthalyl hydrazide itself. This salt can be prepared in anhydrous condition by the addition of ethyl alcohol to an aqueous solution of phthalylhydrazide in excess hydrazine hydrate and drying the resultant precipitate. Heat treatment of the anhydrous salt up to 180°C. under a pressure of 0.05 mm. of mercury in a vacuum distillation apparatus connected to a receiver cooled to about -40°C. gives a 92% 3deld of anhydrous hydrazine. 

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