Nitrostarch preparation

Differences in heats of formation of the two kinds of Nitrostarch are regarded by these authors as related to the presence of sulfuric esters in the Nitrostarches prepared by means of mixed acids... 

Soluble starch was nitrated by Syniewskl (Ref 9). The most extensive published researches devoted to the preparation, purification and properties of nitrostarch are those of Hackel and T. Urbanski (Ref 12) ... 

Nitrostarch can be prepared by dissolving starch in an excess of nitric acid and pouring this solution into an excess of sulfuric acid to precipitate NS as an amorphous powder. This method is uneconomical and hard to control. Consequently it is not used commercially... 

Nitrostarch can also be prepared via nitration with nitric and phosphoric acids (Ref 12) N20s dissolved in nitric acid (Ref 14) N205 dissolved in chloroform (Ref 18) or nitric acid withP205 (Ref 23)... 

The most important of the carbohydrate esters of nitric acid are the polysaccharide nitrates, particularly cellulose nitrate or nitrocellulose (NC) and starch nitrate ( nitrostarch ) which is much less used. Nitric esters prepared from other sugars such as saccharose and lactose are not of any importance as explosives. 

Experimenting with a still stronger nitric add, sp. gr. 1.52, Will and Lenze [1] prepared nitrostarch characterized by a nitrogen content of 14.04%. They established that it is possible to produce nitrostarch of high nitrogen percentage and adequate stability providing it is subjected to a stabilization boil in ethyl alcohol. 

On account of such strong degradation, the viscosity of nitrostarch solutions is low whatever the preparative method applied. Likewise large differences in the viscosities of starch before nitration exert practically no influence on the viscosity of the nitrated product. Experiments carried out by T. Urbanski and Golofit [34] provided the data needed to determine the viscosity of starch (in Parlow degrees) and the viscosity of nitrostarch obtained by nitration with nitric acid, sp. gr. 1.50, followed by precipitation with water. The results are collected in Table 105. 

Nitrostarch of 12.6% N can be prepared, if starch dissolved in ten-fold quantity of nitric acid is poured into 40 times its volume of 94% sulphuric acid, at a temperature not exceeding 20°C. Such nitrostarch includes 11.4% of substance soluble in alcohol, and 95.7% of substance soluble in ether-alcohol. 

In all experiments with nitrating acid prepared by mixing nitric and sulphuric add at a weight ratio higher than 6, the nitrostarch was separated by drowning the whole in water. 

Nitrostarch, with various nitrogen contents (12-13.3%), is prepared by nitration of starch with nitric acid or nitrating mixtures. The resulting crude product is washed in cold water and is then dried at 35-40 °C (95-100 °F). 

Nitrostarch resembles nitrocellulose in several respects, but, owing to its poor stability, difficulty in preparation and hygroscopicity, it is not used anywhere outside the USA. Fleadache-free industrial explosives are based on nitrostarch. 

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