other nitration, as from the nitration of glyccrin. The product resembled the xyloidine of Braconnot, ¡showed a very poor stability, and could not be stored or handled safely in the dry condition. The pulverulent, dusty form of the dry material probably also contributed to the disrepute into which it fell in Europe. In this country starch' is nitrated with mixed acid in which it does not dissolve, and the product retains the. appearance of ordinary starch, as guncotton retains the appcarance of cotton.
Cassava or tapioca starch was preferred at first, for it was «claimed that it contained less fat than corn starch and that the
Figure 69. Nitrostarch Granules (about 30X).
granules, being smaller than those of corn and potato starch, permitted a more uniform nitration and a more efficient purification. Since 1917 corn starch has been used in this country. The starch is first freed from fats and from pectic acid by washing with dilute caustic soda or ammonia solution and then with water, and it is dried until it contains less than 0.5% of moisture. In one process which produced a nitrostarch containing 12.75% nitrogen, a mixed acid containing 38% of nitric acid and 62% of sulfuric acid was used, 800 pounds of the acid in a single nitrator for 200 pounds of starch. The initial temperature of the acid was 32°, the mixture was agitated by a mechanical stirrer having a downward pitch, and the temperature during the nitration was kept between 38° and 40°. At the end of the nitration
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