Part 4 (1/2)
NITRATION OF CELLULOSE, HYDROCELLULOSE, AND OXYCELLULOSE.
LEO VIGNON (Compt. rend., 1898, 126, 1658-1661).
(p. 38) Repeated treatment of cellulose, hydrocellulose, and oxycellulose with a mixture of sulphuric and nitric acids in large excess, together with successive a.n.a.lyses of the compounds produced, showed that the final product of the reaction corresponded, in each case, with the fixation of 11 NO groups by a molecule containing 24 atoms of carbon. On exposure to air, nitrohydrocellulose becomes yellow and decomposes; nitro-oxycellulose is rather more stable, whilst nitrocellulose is unaffected. The behaviour of these nitro-derivatives with Schiff's reagent, Fehling's solution, and potash show that all three possess aldehydic characters, which are most marked in the case of nitro-oxycellulose. The latter also, when distilled with hydrochloric acid, yields a larger proportion of furfuraldehyde than is obtained from nitrocellulose and nitrohydrocellulose.
~CELLULOSE NITRATES-EXPLOSIVES.~
(p. 38) The uses of the cellulose nitrates as a basis for explosives are limited by their fibrous character. The conversion of these products into the structureless h.o.m.ogeneous solid or semi-solid form has the effect of controlling their combustion. The use of nitroglycerin as an agent for this purpose gives the curious result of the admixture of two high or blasting explosives to produce a new explosive capable of extended use for military purposes. The leading representatives of this cla.s.s of propulsive explosives, or 'smokeless powders' are ballist.i.te and cordite, the technology of which will be found fully discussed in special manuals of the subject. Since the contribution of these inventions to the development of cellulose chemistry does not go beyond the broad, general facts above mentioned, we must refer the reader for technical details to the manuals in question.
There are, however, other means of arriving at structureless cellulose nitrates. One of these has been recently disclosed, and as the results involve chemical and technical points of novelty, which are dealt with in a scientific communication, we reproduce the paper in question, viz.:--
A RE-INVESTIGATION OF THE CELLULOSE NITRATES.
A. LUCK and C. F. CROSS (J. Soc. Chem. Ind., 1900).
The starting-point of these investigations was a study of the nitrates obtained from the structureless cellulose obtained from the sulphocarbonate (viscose). This cellulose in the form of a fine meal was treated under identical conditions with a sample of pure cotton cellulose, viz. digested for 24 hours in an acid mixture containing in 100 parts HNO_{3}--24 : H_{2}SO_{4}--70 : H_{2}O--6: the proportion of acid to cellulose being 60 : 1--. After careful purification the products were a.n.a.lysed with the following results:
Soluble in Nitrogen Ether alcohol
Fibrous nitrate 13.31 4.3 p.ct.
Structureless nitrate 13.35 5.6 ”
Examined by the 'heat test' (at 80) and the 'stability test' (at 135) they exhibited the usual instability, and in equal degrees. Nor were the tests affected by exhaustive treatment with ether, benzene, and alcohol.
From this it appears that the process of solution as sulphocarbonate and regeneration of the cellulose, though it eliminates certain const.i.tuents of an ordinary bleached cellulose, which might be expected to cause instability, has really no effect in this direction. It also appears that instability may be due to by-products of the esterification process derived from the cellulose itself.
The investigation was then extended to liquids having a direct solvent action on these higher nitrates, more especially acetone. It was necessary, however, to avoid this solvent action proper, and having observed that dilution with water in increasing proportions produced a graduated succession of physical changes in the fibrous ester, we carried out a series of treatments with such diluted acetones.
Quant.i.ties of the sample (A), purified as described, but still unstable, were treated each with five successive changes of the particular liquid, afterwards carefully freed from the acetone and dried at 40C. The products, which were found to be more or less disintegrated, were then tested by the ordinary heat test, stability test, and explosion test, with the results shown in the table on next page.
In this series of trials the sample 'A' was used in the condition of pulp, viz. as reduced by the process of wet-beating in a Hollander. A similar series was carried out with the guncotton in the condition in which it was directly obtained from the ester reaction. The results were similar to above, fully confirming the progressive character of the stabilisation with increasing proportions of acetone. These results prove that was.h.i.+ng with the diluted acetone not only rendered the nitrate perfectly stable, but that the product was more stable than that obtained by the ordinary process of purification, viz. long-continued boiling and was.h.i.+ng in water. We shall revert to this point after briefly dealing with the a.s.sociated phenomenon of structural disintegration. This begins to be well marked when the proportion of acetone exceeds 80 p.ct. The optimum effect is obtained with mixtures of 90 to 93 acetone and 10 to 7 water (by volume). In a slightly diluted acetone of such composition, the guncotton is instantly attacked, the action being quite different from the gelatinisation which precedes solution in the undiluted solvent. The fibrous character disappears, and the product a.s.sumes the form of a free, bulky, still opaque ma.s.s, which rapidly sinks to the bottom of the containing vessel. The disintegration of the bulk of the nitrate is a.s.sociated with
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Proportions by volume
________________________
Temperature
Heat
Heat
of
Test
Test
Acetone
Water
Explosion
80
134
___________________
______________
_________
_____________
_______
_______
__
Deg.
Mins.
Mins.
20
80
137
3
4
30
70
160
3
4
40
60
180
7
18
No
fumes
after
From 'A' sample.
50
50
187.5
55
100
60
40
187
45
100
70
30
185
45
100
80
20
50
100
__