Nitrocotton Nitrogen

Fig. 92. Absorption of acetone by nitrocottons of various nitrogen content, at the acetone activity of 0.64 according to Rubenstein [43].

An increase of the nitrogen content is also accompanied by an increase of viscosity, providing that the nitrocotton is prepared under accurately uniform conditions. This relationship is described by Berl and Klaye [77] as tabulated below (Table 51). 

Duclaux et al. [101] came to other conclusions for he established that particular fractions differed only in the viscosity of solutions the nitrogen content being the same. In order to precipitate nitrocotton from its acetone solutions the authors added acetone-water mixtures, richer and richer in water until finally pure water was added. A range of fractions was separated from nitrocellulose acetone solution of viscosity 0.1 P (poises). The viscosity of the first fraction was 0.603 P, and that of the last 0.007 P (2% solutions). 

A range of nitrocotton samples containing from 11.3 to 13.1% N, and nitro-ramie of 10% N prepared by denitrating nitroramie of 13% N by acting with nitric acid 80%, have been fractionated by G. G. Jones and Miles [HO] by a method of successive extraction with aqueous acetone every subsequent solvent was richer in acetone than the preceding one. They demonstrated that particular fractions differed in nitrogen content and viscosity. 

Kruger [113] tried fractionating nitrocellulose by diffusion. The principle of the method was that a nitrocellulose solution in acetone, methyl alcohol or amyl acetate diffused into a pure solvent layer on the surface of the solution. Clearly molecules of smaller size penetrate more rapidly. A nitrocellulose solution of 12.8% N was separated into two layers in this way after 42 days diffusion. The lower fraction comprised nitrocotton with a nitrogen content of 13.1% N, the upper layer one of 12.1% N. 

Lhoste has also drawn attention to the fact that the rate of removal of sulphuric acid from nitrocellulose depends on its nitrogen content. The more highly nitrated the nitrocotton, the more slowly sulphuric add is eliminated from it. Thu s in the instance of nitrocellulose of 13.40% N, a 100 hours boiling is necessary to attain the same sulphuric add content as that of nitrocellulose with 12.19% N-content boiled for lOhr. 

Insufficiently purified, non-stabilized nitrocotton demonstrates a variable value of An/At. The evolution of nitrogen as a function of time is illustrated in the diagram (Fig. 112). The curves I-IV relate to nitrocellulose of a high nitrogen content (13% N) boiled in water for different periods from 30 to 100 hr. The longer the time of boiling, the more the curve approaches a straight-line. Finally, after 100 hr... 

Will and other contemporary workers assumed that nitrogen evolved during the thermal decomposition of nitrocotton occurred chiefly as nitrogen oxide. On the... 

According to Goujon [10] heating nitrocotton in a carbon dioxide medium causes the nitrogen to evolve chiefly in the form of N02 and NO. In addition some N2 and N20 are produced. Hydrogen is evolved mainly as H20, carbon as C02 and to a smaller extent as CO. Traces of hydrocarbons are also formed. 

Desmaroux [73a] followed the decomposition of nitrocotton kept at a temperature of 132°C and established that the reaction types (1) and (3) predominated. Only j-j of the substance broke down by the hydrolysis of ester groups. Desmaroux also determined the loss of weight of the sample so as to compare it with the loss of nitrogen. The weight loss of the nitrocellulose calculated on the basis of the nitrogen lost is 3-12 times smaller than the total weight loss, as seen from the data in Table 66. 

P — the loss in weight of 1 g of nitrocotton, N — the nitrogen content (in per cent). R — the PfcN0—N) ratio, where N0—N is the loss in weight of 1 g substance calculated from the loss of nitrogen. 

Lower nitrated types of nitrocotton lose their nitrogen to a smaller degree than higher nitrated types, as would be expected. 

In addition to the three main types of reaction involved in nitrocellulose decomposition, the author assumes that secondary reactions also occur originating in the chemical combination between oxides of nitrogen and water vapour to produce nitric and nitrous acids, which in turn react with the nitrocellulose. By heating nitrocotton with dilute nitric acid at 40°C, Desmaroux found in this instance that hydrolytic and oxidation reactions predominate, causing a weight loss of +-J of the total loss (see Table 67). 

Tn one of the experiments, a denitration of the nitrocotton without any perceptible loss of weight was observed. This showed that nitrocellulose of low nitrogen content (12.13%), was denitrated with ease, and is in good agreement with Vieille s observation (mentioned above), that lower nitrated nitrocellulose was more easily decomposed when boiled with an acid. Gelernter et al. [96] examined the decomposition of nitrocellulose (10.8-11.8% N) labelled with 15N at 157°C and found the secondary 0N02 groups less stable than those of C6. 

T. Urbanski and Malendowicz [76] have examined the rate of decomposition of nitrocellulose by ultra-violet light. The results showed (T. Urbanski [77]) that nitrocellulose of 13.3% N undergoes decomposition expressed by an exponential equation, whereas lower nitrated nitrocotton, 11.9% of N, decomposes approximately in accordance with a linear function. Somewhat discordant results were published by Oguri, Takei and Fujita [78] who reported the fall in nitrogen content of nitrocellulose to be 1.0% N, after 3 hours irradiation, and 1.95% N after 8 hr. 

Milus [84] investigated the explosive decomposition of nitrocotton with different nitrogen content and obtained experimental data which he used to calculate the values tabulated below (Table 68). 

Jessup and Prosen deduced for nitrocotton an equation that expresses the heat of combustion and the heat of formation as functions of the nitrogen content ... 

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