Nitratability of three different polymeric dextrans with predominantly α‐1,6‐linked anhydro‐D‐glucopyranose units was studied in different nitrating agents. The degree of substitution (D. S.) increases with increase of the absolute nitric acid/dextran ratio. Due to gelatinization of dextrans in this medium, this nitrating agent is comparatively less effective for dextran nitration than for starch with predominantly α‐1,4‐D‐glycosidic linkages; the latter has great affinity to dissolution in this medium. Nearly complete nitrations (D. S., 2.96) were readily obtained from dextrans by nitration in presence of 25% each of acetic acid and acetic anhydride.
In nitric‐sulphuric acids mixtures the nitratability of dextran is mainly a function of acids composition. Gelatinization occurred in mixed acids containing up to 20% H2SO4. Successful nitrations (D. S., ca. 2.6) were always obtained, however, from mixed acids containing 38% or more sulphuric acid, but the use of 62% sulphuric acid is more economic for industry. The sulphate content is greatly dependent on the acids composition and it is, as well, affected by the chemical nature of the corresponding dextran.
Whole starch, an~ylose, amylopectin, and glycogen (polymeric carbohydrates of the a-D-glycosidic linkage type) were nitrated by nitric acid in the presence of phosphoric anhydride and stability properties of the nitrated products were studied. Crude amylose nitrate is more stable than a~nylopectin nitrate and the latter is less stable than the whole-starch nitrate a s judged by the Bergmann-Junk test. The stability of glycogen nitrate is closely similar to that of amylopectin nitrate.Appreciable stabilization of the crude nitrates mas brought about by boiling with slightly allcaline water for long periods (60-70 hours). All stabilized samples were found to possess closely si~uilar stability properties. The Bergmann-Junk values of all examined nitrates ranged from 2.2 to 1.7 mg of nitrogen per gram sample; the latter value seems to represent the maximum stabilization which could be attained for the polymeric carbohydrate nitrates of the a-D-glycosidic linkage type. In the case of cellulose nitrate (6-D-glycosidic linkage type) Bergmann-Junk values of 1 to 1.25 mg of nitrogen were obtained.
Oxidative decomposition of cellulose nitrate into a completely watersoluble material is accomplished by an aqueous digestion method that involves boiling it with water under pressure. Sulphate is quantitatively liberated, and most of the nitrate groups are decomposed, thus minimising errors from co-precipitation of the nitrate ions. The digests, which are completely free from inorganic additions, allow rapid sulphate determination by direct titrimetric procedures.
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