Absorption of nitric acid by cellulose and nitrocellulose

The absorption of nitric acid is a phenomenon preceding nitration. Afterwards nitric acid is also absorbed by the nitrocellulose formed. This phenomenon has been examined under various conditions e.g. the absorption of nitric acid in vapour form and the absorption of HN03 from pure nitric acid and from its solution respectively. 

Wilson and Miles [12] have measured the absorption of nitric acid by treating with it nitrocotton of 13.8% N. Under a pressure of 4 mm Hg as much as 15% of HN03, was absorbed by this nitrocotton. Nitric acid is absorbed better by a lowernitrated substance, just as the absorption of water vapour is easier in the case of lower-nitrated nitrocellulose. The maximum absorption has been established with nitrocellulose of 7% N. The amount of nitric acid absorbed by cellulose depends on its type. For native cellulose it amounts to about 25% by weight of the cellulose, and approaches 50% for mercerized cellulose. Such differences in the behaviour of different kinds of nitrocellulose indicates that swelling has an appreciable influence on absorption. Mercerized cotton which is more liable to swell simultaneously shows stronger absorption. 

In another investigation by the same authors [13] the absorption of HN03 from aqueous solutions of nitric acid has been investigated. The absorption proceed most effectively, attaining about 50% with nitrocellulose of 13% N, if the latter is immersed in acid containing 80% of HNOa, which has approximately the composition HN03.H20. 

The relevent data are shown in the chart (Fig. 117) which depicts the absorption of HN03 and of water in the presence of vapours produced from nitric acid, 78 to 80% of HN03 

The absorption of nitric acid from the nitrating mixtures is exceptionally interesting and important from the theoretical and practical point of view. It has long been known that nitric acid absorbed from a mixed acid is richer in HN03 than the nitrating acid itself. 

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Absorption of nitric acid by cellulose and nitrocellulose Nitration with mixtures of nitric and sulphuric acids... 

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