^74 MR. ABEL'S RESEARCHES ON GUN-COTTON. 



features of novelty, when compared with the methods of operation prescribed by ScilON- 

 BEIN, BoTTGEB, Otto and others, and pursued upon an extensive scale, for a short time, 

 at Messrs. Hall's gunpowder works, and at Bouchet. Acids of the specific gravity pre- 

 scribed by Von Lenk and mixed in very similar proportions to those which he indicates, 

 were employed ; in some instances the cotton was submitted to a preliminary purifica- 

 tion, as directed by him, and the product, after being washed in water, was also sub- 

 mitted to treatment with an alkaline bath, the mode only of carrying out this process 

 of purification differing somewhat from that which Von Lenk adopts. But the appli- 

 cation, upon a manufacturing scale, of the system which has been pursued under Lenk's 

 direction at the manufactory at Hirtenberg, brings to light several details of considerable 

 value, the adoption of which unquestionably ensures the attainment of greater uniformity 

 and purity of the product of manufacture than could be secured by the earlier modes of 

 operation. • 



The important steps in Von Lenk's system of manufacture are briefly as follows : — 



1. The carded cotton is spun into a loose yarn, varying in size and strength according 

 to the applications it is to receive ; and the yam is made up into hanks of convenient 

 size (weighing about three ounces). 



2. The cotton is submitted to preliminary purification by boiling it for a few minutes 

 in a solution of potassic carbonate, of specific gravity 1'02, separating the alkaline 

 liquid by means of a centrifugal extractor, and washing the cotton thoroughly in water. 



3. The cotton is perfectly dried by artificial heat, immediately before its treatment 

 with acid. 



4. The acid used for the production of the gun-cotton is prepared by mixing one 

 part by weight of nitric acid, of specific gravity 1"52, with three parts of sulphuric acid 

 of specific gravity 1'84. This mixture is allowed to become perfectly cold before use. 



5. The dry cotton is immersed by small quantities (about six ounces, or two hanks, 

 at one time) in a bath of the mixed acids, which is kept as cool as possible. When the 

 cotton has become thoroughly saturated and has been moved about in the acids for a 

 few minutes, it is removed from the bath to a ledge placed over it, where a portion of 

 the acid absorbed is separated by gentle pressure ; the hanks are then transferred to 

 small covered stoneware vessels, in which they are preserved for forty-eight hours, the 

 proportion of acid with which they are allowed to remain saturated for that period 

 being IU'5 parts by weight to 1 of the original cotton. The vessels containing the 

 gun-cotton and acid are kept as cool as possible by being surrounded with water. 



6. The acid removed from the bath by each successive quantity of cotton immersed, 

 is replaced by the addition of a corresponding quantity of the fresh mixtui-e, before 

 another quantity of cotton is treated. 



7. After the lapse of forty-eight hours, the acid is separated from the gun-cotton as 

 completely as possible by mechanical means {i. e. by means of the centrifugal extractors). 

 The expressed acids are not employed again. 



8. The hanks are then drenched with water, singly, as rapidly as possible ; they are 



