IMPURITIES IN COMMERCIAL HYDROCHLORIC ACID. 3l5 
the dry phosphoric acid. With careful manipulation, one 
ounce of phosphorus, being first converted into anhydrous 
phosphoric acid by combustion in dry air, and subsequently 
into glacial phosphoric acid by dehydrating the oil of vitriol, 
would yield about an ounce of the anhydrous sulphuric 
acid. The process, therefore, at the present low price of 
phosphorus, is inexpensive as well as easy of execution. 
It may be well to mention, as a caution to those who are 
not acquainted with the properties of this body, that al- 
though, in its anhydrous and crystalline state, it has none 
of the characters of an acid, not even changing the colour 
of blue litmus, nor attacking the skin when applied to it, 
yet so powerful is its tendency to absorb water and pass to 
the slate of the highly corrosive oil of vitriol, that the addi- 
tion of a few drops of water to it in a bottle causes a dan- 
gerous explosion, from the great and sudden evolution of 
heat which takes place. — Pharm. Journ. 
ART. LXVL— IMPURITIES IN COMMERCIAL HYDROCHLORIC 
ACID. 
By Mr. Thomas H. Savory. 
There are two kinds of hydrochloric acid commonly kept 
by Chemists and Druggists, one of which is recognized as 
pure and fit for use in medicine, while the other is avowedly 
impure, and only adapted for economical and manufactur- 
ing purposes. The pure acid is colourless, while the other 
is always more or less coloured by reason of the impurities 
present. Among the impurities mentioned in Chemical and 
Pharmaceutical works, as most commonly occurring in this 
