The Chemistry of Powder and Explosives - Sciencemadness Dot Org

274
NITRIC ESTERS
other nitration, as from the nitration, of glycerin. 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 m which it docs not
dissolve, and the product retains the appearance of ordinary
starch, as guncotton retains the appearance 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). (Courtesy Trojan Powder
Company )
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