24 CONCENTRATION OF COMMERCIAL NITRIC ACID. 
termination of the question, started by Browne and Swartz, 
at to their being bat varieties of one species, and points 
worth the attention of those whose residence on the spot 
enables them to apply themselves to their solution. — Land. 
Pharm. Journ. 
ART. VI. — CONCENTRATION OF COMMERCIAL NITRIC 
ACID. 
Mr. Redwood laid before the Pharmaceutical meeting a 
specimen of very strong nitric acid, obtained by concentrat- 
ing the ordinary nitric acid of commerce. He observed 
that as an unusual demand had recently arisen for the 
strongest nitric acid, in consequence of its use in the prepa- 
ration of Gun Cotton, he thought it might be acceptable to 
some of the Members of the Society, to be informed of an 
easy and economical method of making such an acid. In- 
dependently of the requirement of this acid for the purpose 
to which he had alluded, the Pharmaceutical Chemist was 
directed to use nitric acid of sp. gr. 1.5, in some of the pre- 
parations of the Pharmacopoeia, and therefore ought always 
to be able to obtain it when required. Acid of this strength 
was not commonly met with in commerce. Some of the 
manufacturers had recently commenced supplying it; but, 
as it is very prone to undergo decomposition, especially if 
exposed to the light, and as the water of the decomposed 
portion is transferred to that which remains, it could not be 
kept for any length of time without becoming weaker that 
the specified strength, and therefore ought to be made in 
small quantities as required. The process which he re- 
commended for concentrating commercial nitric acid, con- 
sisted in mixing it with oil of vitriol, and submitting the mix- 
i 
I 
