316 IMPURITIES IN COMMERCIAL HYDROCHOLIC ACID. 
acid, are iron, sulphuric acid, free chlorine, nitrous acid, 
arsenic, and lead. Sulphurous acid is also mentioned by 
Professor Graham as existing in this acid, but little or no 
notice is taken of this impurity in the works most generally 
referred to by Druggists. 
Some impure hydrochloric acid having been used for 
generating carbonic acid gas in some of the operations con- 
ducted by the laboratory pupils here, the evolved gas was 
found to be largely contaminated with sulphurous acid. 
Subsequent specimens of acid obtained from several differ- 
ent manufacturers afforded similar results; and on sub- 
mitting these speciments to a more careful examination, it 
appeared that sulphurous acid was not only present, but 
formed an important constituent, as the following analyses 
will show : — .. , 
No. 1. 
Sp.gr. at 60° F. 1.166. 
COMPOS 
:tion. 
GRAINS. 
Hydrochloric Acid . 
Sulphurous Acid 
Sulphuric Acid 
Perchloride of Iron 
Water . 
29.9349 
10.8450 
.1538 
.8364 
58.2299 
100.000 
No. 2. 
Sp.gr. at 60° F. 1.163. 
COMPOSITION. 
GRAINS. 
Hydrochloric Acid 
Sulphurous Acid 
Sulphuric Acid 
Perchloride of Iron 
Water . 
.0052 
61.4972 
31.3708 
7.0530 
.0738 
100.000 
