Volume 1
Watts' dictionary of chemistry / revised and entirely rewritten by H. Forster Morley and M.M. Pattison Muir ; assisted by eminent contributors.
- Date:
- 1888-1894
Licence: Public Domain Mark
Credit: Watts' dictionary of chemistry / revised and entirely rewritten by H. Forster Morley and M.M. Pattison Muir ; assisted by eminent contributors. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
742/796 (page 716)
![acid and nitrate of potash and soda, which they found to have the same effect. Although gun- cottons or pyroxylines are generally spoken of as nitro-ceiluloses, they are more correctly de- scribed as cellulose nitrates, since they have not been found to yield amido- bodies on reduction with nascent hydrogen. The following are the general properties of these compounds (Eder): (1) When warmed with alkaline solutions, nitric acid is removed in varying quantities, dependent upon the strength of the solution employed. (2) Treatment with cold concentrated sulphuric acid expels almost the whole of the nitric acid. (3) On boiling with ferrous sulphate and hydro- chloric acid, the nitrogen is expelled as nitric oxide; this reaction is used as a method of nitrogen estimation in these bodies. (4) Po- tassium sulphydrate, ferrous acetate, and many other substances, reconvert the nitrates into cellulose. Several well-characterised nitrates have been obtained, but it is a matter of difficulty to pre- pare any one in a state of purity and without admixture of a higher or lower nitrated body. The following have been described under a no- menclature having reference to a C12 formula : Hexa-nitrate.—C12H14(N03)604 (gun-cotton). Prepared by treating cotton with a mixture of HN03 (S.G. 1-5) 3 parts, and H2S04 (S.G. 1-84) 1 part, for 24 hours, at a temperature not exceed- ing 10°; 100 parts of cellulose yield about 175 of the compound (calc. 183). Insoluble in alco- hol, ether, or mixtures of both, and glacial acetic acid ; with acetone it forms a jelly and is slowly dissolved. It is the most explosive of the series igniting at 160°-170°. Mixtures of sul- phuric acid and nitre do not give this nitrate (Eder). Ordinary gun-cotton may contain as much as 12 p.c. of nitrates soluble in ether- alcohol ; the hexa-nitrate seems to be the only Dne quite insoluble in this menstruum. // - Penta-nitrate.—C,2H15(N03)505. This com- position has been very commonly ascribed to gun-cotton. It is impossible to prepare it in a state of purity by the direct action of the acid on cellulose. It is prepared by dissolving the hexa-nitrate in nitric acid at 80°-90°, cooling to 0°, and adding concentrated sulphuric acid, by svbich the penta-nitrate is precipitated; after mixing with a large volume of water and wash- ing the precipitate with water and alcohol, it is dissolved in ether-alcohol and finally re-pre- cipitated by water. This nitrate is slightly soluble in acetic acid, nearly insoluble in alco- hol containing only a small proportion of ether. Strong potash solution converts it into the di- nitrate. Tetra- and tri- nitrates (collodion pyroxyline) are generally formed together when cellulose is treated with a more dilute acid at a higher tem- perature and for a shorter time than in the case of the hexa-nitrate, e.g. 4 vols. HN03 (1'38), 5 vols. H2S04 (1-84) at 65°-70° for 5-10 minutes. They are freely and equally soluble in ether- alcohol, acetic ether, and mixtures of acetic acid and wood spirit, or alcohol, and are therefore inseparable. They are insoluble in pure alcohol, ether, or acetic acid. On treatment with con- centrated nitric and sulphuric acids they are converted into the higher nitrates. Potash and ammonia convert them into the dinitrate. Di-nitrate C12H18(N03)208is formed as already indicated, and also by the action of hot dilute nitric acid on cellulose. Freely soluble in ether- alcohol, acetic ether, acetic acid, wood spirit, acetone, and absolute alcohol. The further action of alkalis on the dinitrate results in a complete resolution of the molecule. The cellulose nitrates have generally much stronger absorption-affinities for colouring mat- ters than the celluloses. They are much less susceptible of attack by acid oxidants than cellulose itself, and are therefore used in the filtration of solutions containing e.g. chro- mic acid, permanganates, and, of course, nitric acid of any degree of concentration. Nitric acid of S.G. 1*42 has a remarkable toughening ac- tion upon filter paper: the modification is effec- ted by simple immersion, and the paper so treated is increased in strength tenfold, under- going at the same time a contraction amounting, in circles, to about ^0 diameter. The cellulose so treated contains no nitrogen (Francis, C. J. 47, 183). Cellulose and sulphuric acid.—Cellulose is disintegrated and dissolved by the concentrated acid to a colourless solution. The products are sulphates of a series of compounds of which the celluloses and the dextrins may be regarded as the extreme terms. They are easily isolated in the form of Ba salts. The composition of the sulphates may be expressed by the general for- mula C6nII10nOr)n_r(SO1)a.. The variations in composition and in physical properties are func- tions of the temperature (5°-33°) and duration of the action. The limits of specific rotation of these sulphates are [a]j = —3-65 and+ 72-99. These ethereal salts are entirely decomposed by boiling with alcohol: the resulting carbo- hydrates may be regarded as the corresponding alcohols. In composition and properties (e.g. their reactions with iodine) they constitute an extended series, beginning with soluble cellu- loses and terminating in achrodextrin (Honig a. Schubert, M. 7, 455). While it is impossible to determine the mechanism of these successive resolutions of the cellulose molecule with the precision attainable where such changes may be reversed, and therefore completely studied, they certainly establish the typical connection of the celluloses with the simpler carbohydrates, and in a much more complete way than the coinci- dence of empirical formula. Prior to the researches above detailed the initial terms of the transition series had been similarly obtained and described under the term Amyloid, a term selected to indicate their resem- blance to starch. A practical application of the reaction of cellulose with sulphuric acid is found in the manufacture of parchment paper. The process consists in the rapid passage of the paper through the strong acid (S.G. P5-P6) followed by copious washing. The result may be de- scribed as a superficial conversion of the cellulose into amyloid, whereby it acquires the properties which have obtained for it the designation in question (c/. Hofmann, A. 112, 243). Cellulose and chlorine.—Dry chlorine has no action upon cellulose ; the presence of water determines an indirect oxidising action, but there is no direct combination of cellulose with](https://iiif.wellcomecollection.org/image/b21995990_0001_0742.jp2/full/800%2C/0/default.jpg)
