IMPURITIES IN COMMERCIAL HYDROCHLORIC ACID. 317 
No. 3. 
Sp.gr. at 60° F. 1.1638. 
COMPOSITION. 
GRAINS. 
Hydrochloric Acid . 
Sulphurous Acid 
Sulphuric Acid 
Perchloride of Iron . 
Water 
28.7278 
8.4152 
.1562 
.0461 
62.6549 
100.000 
The presence of sulphurous acid in such large propor- 
tions is no doubt principally due to the use of impure salt 
and oil of vitriol in the process of manufacture, the organic 
matter present being oxidized at the expense of some of the 
oxygen of a portion of the sulphuric acid. It may also in 
part arise from the employment of iron retorts, and from 
the application of too high a temperature, which would de- 
compose the bisulphate of soda and liberate the volatile 
anhydrous sulphuric acid, together with sulphurous acid 
and oxygen gas. The method I adopted for estimating the 
sulphurous acid was to precipitate the sulphuric acid with 
chloride of barium, thenlto neutralize the remaining free 
acid with potash — to evaporate the solution to dryness — to 
fuse the resulting salt with nitrate of potash — to dissolve in 
water, and estimate the sulphurous acid originally present 
from the precipitate now afforded with chloride of barium. 
It appeared desirable that the attention of Chemists and 
Druggists should be directed to this subject, as it is evident 
that the common hydrochloric acid of commerce ought not 
to be employed in any Pharmaceutical processes. — Pharm* 
Jour. 
29 
