512 
PHARMACEUTICAL MEETING. 
end of tlie process, Tvlien carefully conducted, a stratum of nitrous ether is 
found floating over an acid liquor. The method referred to under (4) presents 
no advantage over (1) and (2); (5) is the process of the British Pharmacopoeia 
of 1864; and (6) is Liebig’s process, which, although presenting some advan¬ 
tages, is liable to become unmanageable when anything more than small 
quantities are operated upon, and is, in other respects, unsuited for operations 
on a large scale. The last of the methods referred to (7), appeared to me to 
present the greatest probability that a process might be founded upon it 
capable of accomplishing what is required. 
Xopp’s process for the production of nitrous ether, consists in heating a 
mixture of equal volumes of rectified spirit and nitric acid, sp. gr. 1‘36, 
in contact with copper filings, and, when chemical action has commenced, 
withdrawing the heat and allowing the distillation to go on spontaneously. 
This process answers well for the purpose for which it was intended, and 
it was in working with this process and making some modifications in it, 
that I discovered one which appears to present advantages over any other 
process I know for the preparation of spirit of nitrous ether. There ap¬ 
peared to be some difficulty in adopting even a modification of Kopp’s pro¬ 
cess on account of the increased consumption of nitric acid which it in¬ 
volved and the cost of the copper consumed in the process, for the nitrate of 
copper that would be formed, if the process were generally used in a manu¬ 
facture of this extent, would not be likely to find a market. Other substances, 
acting in the same direction as the copper, for deoxidizing the nitric acid, 
were tried, but without much success. I am informed that manufacturers 
sometimes use iron as well as copper stills in making sweet spirit of nitre, 
and thus get better results than are obtained when the distillation is effected 
in glass or stoneware ; but in my experiments I have not obtained any satis¬ 
factory results by the use of iron. Several experiments were made with 
starch, and also with sugar and glycerine. Many j^ears ago, in 1850, Mr. 
Grant, of Bristol, suggested the use of starch instead of copper in Kopp’s 
process ; but in attempting to apply it in the preparation of spirit of nitrous 
ether, with an increased quantity of spirit in contact with the nitric acid, I 
have found that the starch remains undissolved and unaltered in the mixture 
of spirit and acid until so much spirit has been distilled off as to leave the 
nitric acid with about four times its volume of spirit, when nitrous ether be¬ 
gins to be formed. This, however, is just the point at which the ether would 
be formed if there was no starch present. The starch certainly acts bene¬ 
ficially in one respect,—its particles diffused through the mixture of acid and 
spirit cause the liquid to boil more freely and regularly than it otherwise 
would, and the temperature is therefore less subject to variation than it is in 
the distillation of the acid and spirit alone. When the formation of ether 
has commenced the process proceeds satisfactorily for some time, but at last 
a very violent reaction takes place, and nitrous fumes are copiously evolved, 
which, if allowed to pass into the distillate, would render the product unfit 
for use. 
As the starch remains in an insoluble state in the mixture until it is acted 
upon at the end of the process, I thought there might be an advantage in 
substituting some other organic body of a similar description that would be 
soluble in the spirit. Grape sugar and glycerine were thus tried, but with 
no better success than was obtained with starch. In using glycerine, how¬ 
ever, a practical difficulty was experienced; it was found almost impossible 
to distil a mixture of nitric acid, spirit, and gljmerine in a glass vessel, on 
account of the violent bumping which takes place, and which endangers the 
safety of the apparatus. In this resj)ect, therefore, glycerine produces an 
effect the reverse of that produced by starch. 
