Chemical History of Gun-Cotton and Xyloidine. 525 



dition it leaves a carbonaceous residue on combustion, is 

 dissolved by nitric acid, whether of sp. gr. 1'25 or 1*5, and 

 reprecipitated upon dilution. Strong sulphuric acid also 

 dissolves it in the cold, and chars it at a temperature below 

 180°. These two last properties show that the original pyr- 

 oxyline was perfectly free from admixture with this new sub- 

 stance. 



There occurs a considerable decrease of weight through 

 this transformation. In the first experiment 32 grs. of sub- 

 stance operated upon gave 25*82 grs. of the new product; in 

 the second 43*64 grs. of the one yielded 34*68 of the other. 

 Now assuming the increase in the preparation of pyroxyline 

 to be 75 per cent., the weight of the new product above that of 

 the original cotton would be, as calculated from these figures, 

 41*1 and 39*05 per cent. 



When this new product, whether in the fibrous or the pul- 

 verulent condition, was treated with a mixture of equal parts 

 of nitric and sulphuric acids, it increased considerably in 

 weight, and the resulting substance had all the properties of 

 pyroxyline as prepared in the usual manner, 11*16 grs. of 

 the one yielded 13*56 grs. of the other ; the quantity that 

 should theoretically have been obtained, calculating it from 

 the decrease in making the new product, is 13*84 or 14*04 

 grs. Again, 12*35 grs. of the substance as precipitated from 

 solution gave 15*75 grs., the theoretical amount would have 

 been 15*31 or 15*54 grs. This result proves the distinct- 

 ness of the new product from xyloidine, a fact that could not 

 have been ascertained from the action of the before-mentioned 

 solvents. 



Whilst engaged in obtaining these results, I also examined 

 the action of nitric acid of various degrees of strength upon 

 pure cotton. By treating it with nitric acid of sp. gr. 1*5 

 I obtained a product evidently different from gun-cotton, but 

 as it did not appear to be homogeneous throughout, I passed 

 on to investigate the action of a weaker acid. That of sp. gr. 

 1*45 gave a substance which proved to be identical with the 

 product of the action of the same acid upon pyroxyline. 

 Upon a repetition of the experiment 68*54 grs. increased in 

 weight 14*61 grs., or 21*31 per cent. — a smaller increase 

 than might have been anticipated, but which may easily be 

 accounted for by the fact that the whole cotton had not been 

 transformed, as was proved by a considerable portion being 

 left undissolved by a boiling solution of potash. Nitric acid 

 ofsp.gr. 1*414 produced the same alteration, but only to a 

 small extent, and after long standing. 23*75 grs. of cotton 

 soaked in nitric acid of sp. gr. 1*516 became a hard mass. 



