ME. ABEL'S RESEAECHES ON GUN-COTTON. 807 



than with the requirements of the formula 



€24H36 0i8, SNgGj, 



recently adopted for gun-cotton by PfiLOUZE and Maury. 



3. If cotton-wool of great purity is digested for a period of about twenty-four hours 

 with a considerable proportion of the prescribed acid-mixture (about 50 parts to 1 of 

 cotton), it sustains an increase of weight ranging between 81-8 and 82-6 upon 100 of 

 cotton. Lower results (between 78 and 80 per cent, increase) are obtained by digesting 

 the cotton for a short period only, or for very considerable periods, by using a limited 

 proportion of the acid (from 10 to 14 parts to 1 of cotton), by employment of acids of 

 slightly lower specific gravities than those specified, and by operating upon cotton of 

 somewhat lower quality. The digestion, for a second or third time, of products which 

 have exhibited a comparatively low increase of weight, in an acid-mixture of the kind 

 first used, or of greater strength, has the efiect of raising the weight of the product to 

 within the higher limits above named. 



The increase in weight which 100 parts of pure cellulose should sustain, theoretically, 

 by complete conversion into a substance of the composition Cg H7 N3 On, is 83'.S, while, 

 if converted into a substance of the formula 



^24^36^18' 5N2G5, 



the increase sustained by it only amounts to 77'8 upon 100 parts. 



4. Cotton-wool always contains, even after careful purification, small proportions 

 of foreign organic substances, the presence of which, in the material submitted to 

 treatment with the acids, must afiect to some extent the quantity of the product 

 obtained. 



5. It is extremely difficult, indeed apparently impossible, even in operating under 

 most favourable conditions upon small quantities of cotton-wool, to convert this sub- 

 stance completely into the highest nitric product — the perfectly insoluble gun-cotton. 

 Small quantities of gun-cotton soluble in ether and alcohol can always be extracted 

 from the products ; the quantities are only minute in the highest laboratory-products, 

 but they are always very appreciable in the most perfect manufacturing products. 

 Their invariable formation must unquestionably cause the increase of weight sustained 

 by cotton to be somewhat less than that which theory would demand. 



6. The long-continued digestion of the gun-cotton in the acid-mixture, the several 

 mechanical operations to which it is submitted in the course of its purification, and 

 above all, the solvent action exerted not only upon certain bye-products, but also upon 

 the gun-cotton itself by the alkaline liquid, in which it is boiled for a short time, are 

 all sources of loss which, in examining into the results of a system of manufacture, must 

 not be disregarded, and the existence of which explains satisfactorily the difference 

 observed between the weights of laboratory-products and those of manufacturing opera- 

 tions. 



7. In accepting the formula proposed by P^louze and Maury for gun-cotton, it 



