GUN-COTTON. 287 



Several compounds may in this way be formed, distinguished 

 from each other by the amount of nitric acid which they contain. 

 For the sake of simplicity they are generally classified under 

 three heads 



Mononitrocellulose C 6 H 8 4 (HN0 3 ) 



Dinitrocellulose C 6 H 6 3 (HN0 3 ) 2 



Trinitrocellulose C 6 H 4 2 (HN0 3 ) 3 



but these proportions are not always strictly observed. As 

 a matter of fact, the formula for cotton is higher than C 6 H 10 5 ; 

 it is a multiple of this quantity. Moreover, the quantity of 

 nitric acid indicated by the third formula is somewhat higher 

 than the maximum quantity that is ever united to the cotton ; 

 in fact, the latter falls appreciably below this value, according 

 to most exact analyses and syntheses. As no other thermal 

 experiments have as yet been made with gun-cotton, we pro- 

 pose to discuss this compound in detail. 



Admitting the formula of cellulose to be 241140020, the for- 

 mulae of gun-cotton that best represent that formed in the 

 experiments are the following: 



C 24 H 20 10 (HN0 3 ) 10) or C 21 H 18 9 (HN0 3 ) U . 



The slight difference between the two formulae is owing to 

 the small quantity of carbon retained in the ashes under the 

 form of carbonate, which is disregarded in the second formula. 

 The latter, however, seems, on the whole, preferable. 



2. Gun-cotton was prepared in a calorimeter by means of 

 nitrosulphuric acid, and under the same conditions as those in 

 the preparation of nitrobenzene (p. 270). 1*188 and 1-241 grm. 

 of dry cotton were used. The reaction being prolonged, the 

 experiment was each time stopped at the end of twenty minutes. 

 The gun-cotton was then washed, dried, and weighed, which 

 gave the proportion of acid fixed. This proportion was found to 

 be somewhat below that corresponding to complete nitration, 

 but the experiment had not lasted long enough for this. In 

 each case 9 equivalents of nitric acid, instead of 10 or 11, were 

 fixed on to C24H 40 20 . 



From the results obtained, we calculate the heat given off to 

 be 102 Cal. for 9HN0 3 ; or, + 11*4 Gal. for each equivalent of 

 fixed nitric acid. We may, therefore, admit that the fixing of 

 11HN0 3 , according to the formula 



CU^A,, + 11HN0 3 - 11H 2 0, 



would disengage 4-125*4 Cal. ; or + 114 Cal. for the formula 

 QJ^Oao 4- 10HN0 3 - 10H 2 0, 



which represents the conventional composition of gun-cotton. 



3. The value + 11 '4 is very near that of + 124 found for 

 nitrostarch, which justifies us to a certain extent in assuming 



