24 
ON PYROXYLIN. 
composed of one part of nitric acid to three of sulphuric acid; that of Bouchet, under 
the name of unequal volumes, is prepared with one part of the first of these acids and 
two of the second, equivalent in -weight to 1 per 2*46. The above-mentioned memoir 
gives, as being most successful, a mixture of three volumes of nitric acid and seven of sul¬ 
phuric acid (by weight 1 to 2-86), proportions very nearly those given by General Lenk. 
At Hirtenberg, the cotton is steeped in portions of 100 grammes in 30 kilogrammes of 
the mixture. It is withdrawn from the bath after being shaken in it for an instant, and 
each time the quantity of mixture absorbed by the cotton is replaced by a fresh amount. 
These operations are continued indefinitely, the weight of the mixture being always 300 
times that of the cotton. 
When the desired quantity of cotton has been steeped, it is put into a receiver, and 
allowed to remain forty-eight hours impregnated by the acids. It is then placed in a 
strainer, where most of the uncombined acids are expelled in a few minutes. 
It is freed from the remainder in a stream of water in which it is washed, and where 
it remains immersed for six weeks, when it is strained a second time, boiled for two or 
three minutes in a solution of carbonate of potash of 2° Baume. After a third and last 
straining, the cotton is dried in the air if the weather is favourable; if not, in a stove of 
which the temperature is not allowed to exceed 20° C. 
General Lenk has latterly made use of a solution of soluble glass of 12° Baume. The 
cotton prepared as above is soaked in it, dried, and exposed to the air for a sufficient 
time to allow the carbonic acid of the atmosphere to combine with the soda of the glass, 
which determines the precipitation of an insoluble silicate, which, according to General 
Lenk, “ encloses the fibres of the cotton, and prevents the development of gases.” 
At Bouchet, the cotton is steeped in vessels containing only 2 litres of mixture for 200 
grammes of cotton, and the steeping is considered complete at the end of an hour. 
About 70 per cent, of non-combined acids are pressed out, the cotton being then 
washed for one or two hours in the river, freed from most of the water by strong pressure, 
and left for twenty-four hours in an alkaline ley to neutralize the last traces of acids. 
Withdrawn from this, it is a second time washed in the river, then pressed, and finally 
dried on a light canvas, through which a ventilator forces cold air. 
Soluble glass has not been tried at Bouchet, hut we are about to show that it is not so 
beneficial as it is supposed to be by General Lenk. 
Quantity of Pyroxylin produced by a given quantity of Cellulose .—A German report, 
signed by MM. Redtenbacher, Schrotter, and Schneider, gives to Lenk’s pyroxylin the 
formula:— 
C 12 H 7 0 7 ,3N0 5 or C 13 H r (NO 4 ) 3 O 10 ,' 
equivalent to the following composition :— 
Carbon ..24*24 
Hydrogen.. 2 36 
Oxygen.59-26 
Nitrogen.14*14 
100*00 
The reaction may be explained in two ways:— 
1. By admitting that by contact with the mixture of nitric and sulphuric acids the 
cotton loses the water, which is replaced by the first of these acids— 
C 12 H 10 O i0 + 3 NO, = C 12 H 7 0 7 ,3 NO s + 3 HO. 
2. By supposing that the hydrogen of the cellulose is replaced by an equal number of 
equivalents of hyponitric acid—• 
A V X xx.- C i2 H i0O 10 + 3NO 5 = C 12 H 7 (NO 4 ) 3 O 10 + 3HO. 
. Acconiing to this, 100. parts of cotton ought to produce 183 of pyroxylin ; but though 
in more rhan 100 experiments w*e have varied the proportions of the bodies producing 
this explosive matter, 178 is the greatest yield we have been able to obtain. 
T re German report is silent on the subject of the yield, which, in our opinion, consti- 
xutes the most solid basis for determining the composition of pyroxylin. We do not say 
that the exact determination of the yield of cotton in pyroxylin renders useless the 
elementary analysis of the latter, but it is necessary that the analysis should agree with 
the figures representing this yield. 
Our experiments on the yields have been made with cotton of good quality, previously 
washed m a boiling solution of carbonate of potash or soap, and then freed as much as 
