ON THE IMPURITIES OF COMMERCIAL ZINC, 83 
by Otto, is therefore an absolutely necessary preliminary to the use of chlorhydric acid 
in any examination for arsenic. 
From the examination of so few samples of sulphuric and chlorhydric acids, we do 
not pretend to have established the affirmative proposition, that there is always arsenic 
in these acids; their impurity was only. an incidental difficulty in this research, 
and we strayed thus far from our main subject, only because of the great impor- 
tance of trustworthy information upon this point to the pharmacist, and to the 
chemist who has to do with poisoning cases. Our observations, in connection with 
the facts long since established regarding the contamination of foreign sulphuric and 
chlorhydric acids with arsenic, may well lead the pharmacist and the analytical chemist 
to distrust his acids, till accurate experiments have proved them to be above suspicion ; 
and we believe that careful investigations will hereafter show that arsenic is introduced 
into pharmaceutical preparations by the acids employed in their manufacture to an 
extent far greater than would now be credited. The task of the chemist who is called 
upon to examine a human body or organs of the body for arsenie, is a simple one 
when the poison is found in its original condition, unabsorbed and unaltered, but in 
difficult investigations of this kind, when the poison has been absorbed and diffused 
through a large mass of organic matter which must be destroyed by acids, the pre- 
cautions insisted upon by Gaultier de Claubry,* and by Galtier,t and other modern 
toxicologists, should be strictly observed. Not only should all the reagents to be em- 
ployed be thoroughly tested à blanc, but furthermore, an experiment parallel with the 
actual examination of the-suspected organic substances should be carried on with the 
same reagents in the same quantities, in a similar apparatus, and in all respects under 
like conditions, upon a quantity of normal animal matter equal to the weight of the 
suspected substances. In this way only can the chemist avoid the fatal uncertainty 
consequent upon the employment, in large quantity, of reagents whose purity is not 
above suspicion. 
We return to the examination of other zincs for arsenic. With the same purified 
acid used in our previous experiments on Pennsylvanian and Vieille Montagne zincs, 
we tested 200 grammes of Silesian zinc, carefully granulated, and perfectly clean. For 
half an hour, the hydrogen passed steadily through the red-hot reduction-tube without 
leaving the slightest deposit in the fine tube beyond the heated portion, but on con- 
* Briand, et Chaudé, et Gaultier de Claubry, Manuel ae de Médecine Légale, 5me édition, (Paris, 
1852,) p. 752. * 
+ C. P. Galtier, Traité de Toxicologie, (Paris, 1855,) Tom. I. p. 362. 
