Nitrocellulose, Cellulose nitrate, Nitrocotton

A white powder which is very easily scattered in a dry state, or a cottonwool-like matter. Molecular weight 426.4 594.3. In practice the nitrogen content varies from 9.0% to 13.4% and 11-12% is the most popular commercially for firework use. Nitrocellulose is soluble in acetone, ethyl acetate, amyl acetate etc. Nitrocellulose which contains less than 12% nitrogen dissolves in a mixture of ether and ethanol in a ratio 2 1 by volume. This solution can produce a stronger film of nitrocellulose than one in acetone. 

It is important to keep it in a wet state with water or ethanol during storage. Never scatter it because it becomes a dangerous inflammable dust floating in the air. It is used as a solution in acetone or amyl acetate and is known as NC paste , for the consolidation of compositions which contain magnesium. 

Manufacture. Linter or cotton waste is purified by boiling it in a dilute NaOH solution and well dried. It is dipped into a mixed acid which consists of sulphuric and nitric acids in a weight ratio about 7 3. The ratio of the cotton linter to the mixed acid is about 1 50 by weight. 

It is kept at room temperature for 2.5 hours and the linter is then nitrated to the nitrocellulose. The required nitrogen content is obtained by adjusting the water content in the mixed acid for example, about 17.5% H2O is adequate to obtain 12% N. The nitrated linter is separated from the mixed acid. It is washed with water and boiled in a 0.01% Na2COj solution in water for about two days renewing the solution several times in order to remove traces of acid. Lastly it is beaten in water with a beater to form fine particles and finally washed with hot water until it passes a heat resistance test. 

Quality. JIS standard (K 6703) shows two grades of nitrogen content, L 10.7-11.5% N and H 11.5-12,2% N which are easily obtained on the market. They are further classified by viscosity into various kinds and 

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Certain differences in numerical data reported in various publications can be justified to some extent by differences in the analytical methods used. On the other hand, the values given by Lhoste seem to show that the sulphuric acid in nitrocotton could be combined with nitrocellulose molecules less firmly than in an ester group. For instance, it is not out of the question that sulphuric add may be bound with nitrocellulose as an inclusion (clathrate) compound. (Attention was also drawn to this point by Miles [15] in his monograph on cellulose nitrate.)... 

CAS 9004-70-0 EINECS/ELINCS 239-069-9 UN 2059 (DOT) UN 2555 (DOT) UN 2556 (DOT) UN 2557 (DOT) Synonyms Celloidin Celluloid Cellulose nitrate Cellulose tetranitrate Collodion Collodion cotton Collodion wool Colloxylin Flexible collodion Guncotton Nitrocellulose, dry Nitrocellulose sol n. Nitrocellulose, wetted Nitrocotton Nitron Fyor lin Pyroxylin plastic Pyroxylin rods Soluble guncotton Xyloidin Classification Cellulose deriv. 

As shown experimentally by Piest [75], cotton which was subjected to various operations, e.g. bleaching, treatment with alkalis or acids, strong heating prior to nitration furnishes nitrocellulose solutions of low viscosity. At the same time an increase in the solubility of the nitrocotton was also observed. This is evidence that the cellulose molecules are shortened and their content of terminal group is increased. A certain proportion of hydrocellulose and oxycellulose may result. The total effect is to bring about an increase in the reductive properties of the cellulose, i.e. an increase of the copper number. 

The absorption spectrum of nitrocellulose solutions has been examined (Rassow and Aehnelt [135]). It has been established that the capacity to absorb light differs with the origin of the nitrated cellulose. Thus nitrocellulose made from wood pulp gives a slightly different absorption spectrum from that of nitrocotton. 

An interesting observation has been made while attempting to purify nitrocotton by dissolving it in acetone followed by predpitation with water. Guncotton (sample 1) was fairly well purified and stabilized by this method, but collodion cotton (sample 4) retained almost the whole amount of add present in it before purification and it was just as unstable as before, because the sulphuric esters were dissolved and reprecipitated with the nitrocellulose. Inddentally this is convincing chemical evidence confirming the existence of sulphuric acid cellulose esters in lower nitrated cellulose. 

Similar observations were also published earlier by Tribot and Marsaudon [16]. Recently, however, Lhoste [17] has questioned the validity of the hypothesis of the formation of sulphuric acid esters during the nitration of cellulose. On the basis of analytical data the author has arrived at the idea that sulphuric acid is bound with nitrocellulose solely by occlusion. He found no evidence to confirm the existence of cellulose sulphates in nitrocotton. 

According to the classical work of Abel [3] the instability of nitrocotton samples is caused not so much by the tendency of nitrocellulose to decompose, as by the presence of certain impurities. Abel showed that the purest nitrocellulose was so resistant to decomposition by heating that it could withstand the action of a temperature between 65 and 100°C even for several months. He also demonstrated that low-nitrated cellulose added to guncotton does not exert an adverse effect on the latter s stability and its capacity to withstand the heat test. 

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. 

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