PRESENCE OF ARSENIC. 613 
merce containing arsenic, it cannot but be expect- 
ed that many of the ingredients or compounds 
into which that acid enters as a constituent, as 
well as some of those of which it is not a consti- 
tuent, but in the formation of which it has been 
employed as an agent, will be liable to be more 
or less contaminated with arsenic. I have detected 
arsenic in the sulphate of potash (commonly 
known in chemical manufactories under the name 
-of “sal enixum’’), though in the formation of 
this salt a considerably high temperature had been 
employed, which many persons probably might 
suppose would have had the effect of expelling all 
the arsenic. ‘There is reason to expect its pre- 
sence in alum, not only since such sulphate of 
potash as I have mentioned is used in alum 
making, but also as sulphuric acid is directly 
applied in the formation of the sulphate of alumina 
used.* And, the probability arises, that food may 
in some instances be contaminated with it; alum 
being an article which bakers often use in admix- 
ture with the other usual constituents in the mak- 
* Since writing the above, I have obtained a commercial 
sample of alum, which had been produced by the aid of 
pyrites sulphuric acid, and found it to be accompanied by a 
trace of arsenic. 
