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(about 4 liters), and allowed to crystallize by standing over night. Yield 300-310 grams, about of the theory.

The rapid cooling of a solution of a-nitroguanidino produces small needles, which dry out to a fluffy mass but which are still too coarse to be incorporated properly in colloided powder. An

Ftouu 89. a-Nitroguanidine (25X). Small crystals from the rapid cooling of a hot aqueous solution.

Ftouu 89. a-Nitroguanidine (25X). Small crystals from the rapid cooling of a hot aqueous solution.

extremely fine powder may be procured by the rapid cooling of a mist or spray of hot nitroguanidine solution, either by spraying it against a cooled surface from which the material is removed continuously, or by allowing the spray to drop through a tower up which a counter current of cold air is passing.

Preparation of ^-Nitroguanidine. Twenty-five cc. of 61% aqueous sulfuric acid is poured upon 20 grams of dicyandiamide contained in a 300-cc. round-bottom flask equipped with a reflux condenser. The mixture warms up and froths considerably. After the first vigorous reaction has subsided, the material is heated for 2 hours in an oil hath at 140° (thermometer in the oil). The reaction mass, chilled in a freezing

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