of preparing and employing Gun-cotton. 537 



manufacture by reactions between the elements of the com- 

 pound. 



General von Lenk does not deny the reactions which may cause 

 the inflammation of the gun-cotton when they disengage a suf- 

 ficient heat ; but he thinks they may be avoided by taking the 

 precautions which he has recently made known. 



His method depends on the same reactions as those used in 

 the powder works at Bouchet seventeen years ago, and which 

 are described in a memoir of the 17th of February 1849. The 

 Austrian, like the French gun-cotton, is a compound pro- 

 duced by the immersion of cotton in a mixture of nitric and 

 sulphuric acids. Their proportions may be varied within toler- 

 ably wide limits without modifying the quality of the product. 

 Yet as the most successful the author of the memoir of 1849 

 mentions a mixture of 3 volumes of nitric acid with 7 of sul- 

 phuric acid, equal in weight to 1 of nitric to 2*86 of sulphuric 

 acid. This is almost the ratio of 1 to 3 adopted by General von 

 Lenk. At Hirtenberg each acid is admitted into the mixing- 

 vessel by a small orifice, in order to moderate the increase of 

 temperature. At Bouchet, where this precaution was not taken, 

 an increase of about 20° was observed ; but the mixture was pre- 

 pared sufficiently long beforehand to allow it to sink to the 

 temperature of the surrounding air before the immersion of the 

 cotton. 



Moreover differences of this kind could have no influence on 

 the qualities of gun-cotton. We shall describe those to which 

 General von Lenk attaches most importance. According to 

 him, the Bouchet method, in which 200 grammes of cotton are 

 immersed in a litre of the mixture, would not give the same pro- 

 duct as that obtained by working with a much larger propor- 

 tion of the mixture and by means of a special apparatus. This 

 apparatus is a rectangular trough, divided longitudinally into 

 three compartments, and kept at the temperature of a current 

 of water which circulates between double sides. The first is a 

 reservoir which supplies the second with the mixture, so as to 

 have constantly a bath of 30 kilogs. for 100 grammes of cotton. 

 The cotton is thus immersed in 300 times its weight of acids. 

 It is stirred, and as soon as it appears completely soaked with 

 acid, which only requires about a minute, it is placed on a small 

 strainer over the bath and subjected to a regulated pressure, so 

 as always to leave the same weight of acids. With a little skill 

 1*150 kilog. is obtained as the weight of the pressed mass; 

 hence 100 grammes of cotton take 1*050 kilog. from the bath. 

 These operations are constantly repeated on the same bath, re- 

 placing each time by 1*050 kilog. of the new mixture that which 

 the cotton has removed. 



Phil. Mag. S. 4. No. 192. Supph Vol. 28. 2 N 



