Chemical History of Gun-Cotton and Xyloidine. 521 



upon employing two measures of sulphuric acid to one of 

 nitric acid, 1 obtained a product resembling in all respects 

 ordinary pyroxyline, yet 42*77 grs. gave an increase of only 

 24-31 grs., or 56*84 per cent. Upon a repetition of this ex- 

 periment I found the increase to be 59*93 per cent., and again 

 70*6 per cent. Suspecting from the disparity of these results 

 that something might be dissolved in the acid liquor, I im- 

 mersed 6*7 grs. of cotton in a large quantity of the mixed 

 acids, but it increased 4*9 grs., or 73*1 per cent. Perceiving 

 that I had obtained an opposite effect to that anticipated, I 

 treated 12*64 grs. of cotton with just sufficient of the mixture 

 to wet it thoroughly : the fibre was evidently somewhat de- 

 stroyed ; the increase in weight was only 6*54 grs., or 51 '74 

 per cent., and the acid liquor squeezed from the cotton, neu- 

 tralized with ammonia, evaporated to dryness, and heated, 

 gave abundant evidence of organic matter being present. 

 Lest however it might be supposed that the whole had 

 not been converted into pyroxyline, it was treated again with 

 the mixed acids, but that produced an increase of only 0*12 

 gr. The action of various solvents confirmed its identity 

 with ordinary pyroxyline, while its solubility in potash proved 

 that the transformation had been very nearly complete. A 

 repetition of the experiment gave similar results. It thus 

 appears that the small increase in weight in the preparation 

 of pyroxyline takes place when there is not sufficient nitric 

 acid present to prevent the peculiar action of the sulphuric 

 acid, namely, that of dissolving and altering it. When how- 

 ever the increase amounted to about 74 per cent., I was never 

 able to detect the presence of oxalic acid or other organic 

 matter in the acid liquor ; and as no gas is evolved during 

 the'preparation of pyroxyline, it may be concluded that there 

 is no secondary product containing carbon. 



Subsequently, when Dr. Schcinbein had specified his me- 

 thod of making gun-cotton, I treated 18*78 grs. of cotton 

 with a mixture of three parts of sulphuric acid and one of 

 nitric acid, sp, gr. 1*5, following his directions. The result 

 was 32*92 grs. of a substance similar to that produced in 

 former experiments, being an increase of 75*20 per cent. On 

 another occasion SO* 95 grs. of cotton gave an increase of 

 61*10 grs., or 75*47 per cent. The action of solvents and re- 

 agents confirmed the identity of this pyroxyline with that 

 obtained in my previous experiments, and I was equally able 

 to establish the absence of any secondary product containing 

 carbon. 



In determining the ultimate composition of pyroxyline 

 several precautions were found to be necessary. In the ana- 



