ON PYltOXYLIN. 
25 
possible from foreign bodies, particularly from cotton seeds. Before being used, it was 
carefully dried in a Gay-Lussac stove, between 100° and 115°. 
The sulphuric acid marked 6G° on the Baume areometer. The nitric acid had a den¬ 
sity of 1*500 at 9°; it was yellow and slightly nitrous. 
The relative proportions of the sulphuric and nitric acids were varied so as to present, 
1. The composition of Lenk’s mixture; 2. That of the unequal volumes of Bouchet; 
3. Various intermediary proportions between 2 and 3 of sulphuric acid for 1 of nitric 
acid. 
The relative proportions of acid mixture and the weight of cotton were also varied, in¬ 
cluding those formerly used at Bouchet, and those indicated by General Lenk, until the 
weight of the acids was 500 times that of the cotton. 
The duration of the immersion of the cotton in the acids varied from 1 to G6 hours. 
In all these experiments the yields differed very little, never exceeding 178 per cent, 
of cotton. 
The yield in manufactories whether at Hirtenberg or Bouchet is far from being so 
large as that obtained with small quantities in the laboratory. In fact, General Lenk 
says, that it requires 64*500 kils. of undried cotton to produce 100 kilogrammes of pyroxy¬ 
lin, which corresponds to a yield of 155. Supposing the cotton to contain 6 or 7 per 
cent, of moisture, the yield of dry cotton at Hirtenberg would have been from 165 to 
167 per cent. 
The yield at Bouchet, after the working had become regular, was 165*25 per cent. 
Though unable to draw from these numbers any conclusion as to the theory of the 
formation of pyroxylin, we cannot pass over in silence a circumstance as important as 
the yield,—so to speak, identical with it,—obtained on a large scale in the two factories. 
Composition of Pyroxylin .—In 1847 we determined the composition of pyroxylin, and 
represented it by the following formula—C o 4 H 17 0 i; ,5N0 5 . 
We must first find out whether we operated on a product different to Lenk’s pyroxylin, 
and, if the two are chemically identical, whether this formula is correct. 
We have conducted these researches with the greatest possible care, and believe we 
have surmounted the difficulties of the combustion of pyroxylin. We found the py¬ 
roxylin of Hirtenberg and Bouchet chemically identical, and found for them a formula 
differing from the previous one by only one equivalent of water. 
This formula is C 24 H 1S 0 18 ,5N0.-. 
It is so like the previous formula—C 24 II l7 0 l7 ,5N0 5 —that analysis alone would not be 
sufficient to justify the alteration without being supported by the amount of the yield. 
In fact, the new formula supposes a yield of 177*78 of pyroxylin for 100 of cotton, while 
the old formula corresponds to a yield of only 175. The direct experiments described 
above gave the figure 178. 
All the gun-cottons we analysed were previously washed in a mixture of alcohol and 
ether, to remove some milliemes of fatty and soluble matters, then dried for several hours 
in a stove at a temperature between 40° and 50°. 
All were of the composition above described, and gave the following figures:— 
Carbon.25*00 
Hydrogen.3*13 
Oxygen.59*72 
Nitrogen.12*15 
100*00 
The action of Heat on Pyroxylin .—General Lenk ascribes the unsatisfactory results 
obtained in France by the Commission of 1846 to the fact that not sufficient attention 
was paid to the manner in which the pyroxylin was prepared, and to operating upon an 
insufficiently defined nitred product. By taking advantage of conditions most favoui’able 
to nitrogenization, he believes he has obtained a pyroxylin very difficult to decompose. 
We will not discuss the theoretical value of this assertion, which does not seem to us 
to be very great. It is, on the contrary, more probable that gun-cotton would decompose 
more readily the less like cellulose, and, consequently, the more nitred it became. How¬ 
ever this may be, General Lenk says that pyroxylin made by his process will not explode 
below 136° C. 
We have made this important point the subject of numerous experiments. 
These experiments were first made with an experimental matrass, open or closed, and 
plunged into a bath of boiling water. 
