Nitration with mixtures of nitric and phosphoric acids

NITRATION WITH MIXTURES OF NITRIC AND PHOSPHORIC ACIDS 

The attempt to substitute phosphoric acid for sulphuric acid was first made by Hoitsema [32] and was also investigated independently at the same time by Lunge and Weintraub [15]. Work in this field has been revived by Krauz and Blechta [33], Berl and Ruff [34], Bouchonnet, Trombe, Petitpas [35], Staudinger and Mohr [35a] and Wannow [36]. 

Increasing the content of phosphoric acid above 75% of the total mixture is accompanied by a significant reduction in the reaction rate. The nitrogen content of a product prepared by nitrating with mixtures of HNQ3 and H3P04 is higher 

The recent systematic investigations carried out by Newman et al. [37] were devoted to the viscosity, sedimentation, diffusion and osmotic pressure of nitro-celluloses prepared by nitrating non-purified cotton, purified cotton, and viscose fibres with mixed add containing phosphoric acid and phosphoric anhydride. 

Wannow [36] has stated that the nitration of cellulose by means of mixed nitric and phosphoric acid does not reduce the degree of polymerization of the nitrated substance. The stability of nitrocellulose obtained by treatment with H3P04 and HN03 is 

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Nitration with mixtures of nitric and phosphoric acids Nitration with mixtures of nitric and acetic acid (or acetic anhydride) Nitration in mixtures and solutions including inactive substances Nitration with nitric acid in the presence of inorganic salts Nitration with nitrogen oxides Celluronic acid nitrates (carboxycelluloses nitrates)... 

Nitrocellulose of 14.04% nitrogen was obtained by Berl and Ruff [2], when they nitrated cellulose with a mixture of nitric and phosphoric acid. Later Dalmon [3] has prepared nitrocellulose containing 14.12% of nitrogen by treating cellulose with gaseous N2Os. 

The degradation of nitrostarch is also considerable, if starch is nitrated by means of a mixed acid composed of nitric and sulphuric acid. On the contrary, application of nitrating mixture consisting of nitric acid and ortho-phosphoric acid makes it possible to obtain a product nearly twice as viscous as that obtained by treatment with a mixture of nitric and sulphuric acid (T. Urbanski and Kapu-Scihski [36]). This shows that the mixture of nitric and phosphoric acid causes less degradation of starch than nitric acid alone or mixed with sulphuric acid. Previously, Berl and Kunze [37] had come to the same conclusion. They found the product of... 

Nitration occurs when xylan is treated with nitric acid or mixtures of nitric acid and sulfuric or phosphoric acids.94-108 116 11 The dinitrate prepared by esterification of xylan with a mixture of nitric and phosphoric acids117 is insoluble in most solvents.94... 

When nitric add and sulphuric acid mixed in a 1 2 ratio were used a product containing 8.45% N was obtained with a yield of 55%. O-nitro groups make up 7.1% N whereas the contribution of C-nitro groups was only 1.35%. An approximately equal relationship between the C-nitro and O-nitro groups was reported by these investigators on nitrating by means of mixtures consisting of nitric and phosphoric acid or nitric acid, acetic acid and acetic anhydride. 

One of the arguments against the existence of micelles in solutions of cellulose derivatives is the fact that when cellulose is converted into its derivative, e.g. an ester, the degree of polymerization remains almost unchanged. This however only occurs when ester fonnation is carried out under strictly controlled conditions (nitration at low temperature with nitric and phosphoric acids mixture — p. 341, or with nitric, acetic acids and acetic anhydride mixtures — p. 344). The relevent data found by Staudinger and Mohr [32] are collected in Table 40. 

Experiments on the use of mixtures of nitric add with phosphoric anhydride showed this to be impracticable, since separate layers were formed with the phosphoric acid at the bottom and nitroglycerine remaining dissolved in the nitric add layer from which it had to be separated by adding water. Nor was replacement of sulphuric acid by anhydrous calcium nitrate of any practical value, as predpitation of nitroglycerine by the addition of water was necessary. The yield attained by application of both these methods does not exceed 2 parts of nitroglycerine from 1 part of glycerol. At the time when concentrated nitric add was very expensive, attempts were made to nitrate glycerine with a mixture of sulphuric acid and sodium nitrate (Huntley and Kessel [1]). However, this method found no practical use. 

H. Braconnot showed that an alcoholic soln. of nitric acid is often less active than the aq. soln. He said that the alcoholic soln. acts feebly on bismuth, zinc, and copper because of the low solubility of the nitrates of these metals in alcohol and that it does not attack mercury because of the insolubility of the nitrate in alcohol. P. Pascal discussed the action of mixtures of sulphuric and nitric acids on aluminium, steel, and lead. The addition of sulphuric or nitric acid to a manganic salt or manganese dioxide, in the presence of hydrofluoric, phosphoric, or arsenic acid, may convert the whole of the manganese into the corresponding manganic salt. J. Jannek and J. Meyer found that cone, nitric acid distilled with platinum apparatus contains impurities not found when vessels of fused-quartz are employed. G. P. Baxter and F. L. Grover said that if clean, well-seasoned platinum is used, the results are as good as with quartz provided the acid is free from traces of hydrochloric acid. 

Nitration. As pointed out in Vol. II (p. 321) the only industrial method ol nitrating cellulose consists in using a nitric acid -sulphuric acid nitrating mixture. The other nitrating mixtures, such as nitric acid/phosphoric anhydride, nitric acid/acctic anhydride, nitric acid/chlorinated hydrocarbons were in use occasionally on a laboratory scale to solve some problems connected with the nitration of cellulose. Thus Bennett and Timell (10 confirmed the work of Bouchonnet, Trombe and Petitpas (Vol. II, p. 344) that the nitration of cotton dust with a mixture of nitric acid-acetic acid acelic anhydride (in proportion 43 32 25) at 0 C can yield fully nitrated cellulose, that is, cellulose trinitrate of 14.14% N... 

The most commonly used nitrating medium is mixed acid, i.e., nitric and sulfuric acid mixtures, although mixtures of nitric with phosphoric acid, with acetic anhydride, and 100 per cent nitric acid are also used. The reaction usually proceeds readily at room temperature, and external cooling is frequently necessary to remove the heat of the reaction. 

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