CONCENTRATION OF COMMERCIAL NITRIC ACID. 25 
lure to distillation with a gentle heat. If commercial nitric 
acid, sp. gr. 1.42, be mixed with its own volume of oil of 
vitriol, and distilled by the heat of a sand-bath cautiously 
applied, a quantity of acid, equal to two-thirds that of the 
nitric acid introduced, might be drawn over, and this acid 
would have a specific gravity of 1.514 to 1.52. This pro- 
cess had been recommended some years back by M. Millon, 
and it was the process alluded to in the last number of the 
Pharmaceutical Journal, in the paper on Gun Cotton. 
Millon and other chemists, however, had stated that the 
nitric acid thus obtained, was always contaminated with 
sulphuric acid. Had this been the case, it would have en- 
tirely precluded the adoption of the process for preparing 
nitric acid for pharmaceutical purposes, but he, (Mr. R.) 
had found, from repeated experiments, that if care was 
taken not to apply more heat than was necessary to bring 
over the nitric acid, and not to push the distillation too far, 
the distilled acid was quite free from sulphuric acid, and 
was in every respect as pure as that made by the process 
of the Pharmacopoeia. In some respects, this process pos- 
sessed advantages over that of the Pharmacopoeia; the acid 
produced was stronger, and was less coloured by nitrous 
acid. His object, in alluding to the subjecton this occasion, 
had merely been to direct attention to an easy and econo- 
mical method of obtaining the strongest nitric acid that 
could be made, and at the same time to correct an error 
which had prevailed, to the effect that acid, so prepared, 
was not pure. — lb. 
VOL. xiii. — NO i. 3 
