A new Method for detecting Arsenic. 40 L 



acids themselves, we should be forced to place together the 

 sulphuret of iron, the sulphuret of lead, the sulphuret of 

 zinc, &c. This is not all : the oxygen which should have 

 determined the preeminence granted to the acids of which 

 it is the generator, would obtain it for itself for a stronger 

 reason, relative to its combinations with the metals, known, 

 by the name of metallic oxides, which would still form a 

 single genus. It would remain to mark these places of the 

 native metals in this distribution, and it seems that the only 

 part to take would be to associate them also in one and the 

 same genus. 



[To be continued.] 



LXX. A new Method for detecting Arsenic- By Joseph 

 Hume, Esq., of Long Acre } London. 



To Mr. Tilloch, — Sir, 

 Jl ew chemical tests are so interesting as those which dis- 

 cover the presence of a poison, particularly that of arsenic. 

 It is not merely to the chemist or the mineralogist that such 

 assistance is advantageous, but it is often of the greatest 

 importance to the administration of public justice, where 

 tile innocence or guilt of the accuseu depends frequently on 

 no other evidence than the existence of this most deleterious 

 substance. 



The methods principally adopted are few, perhaps not 

 more than five; and though either of these, in many in- 

 stances, may sufficiently answer the end, yet, when the 

 quantity of the arsenic is extremely minute, I fear these are 

 liable to objections, and the results may be ambiguous. 



The latest observations on this subject are, probably, 

 those of doctor Bostock, which were read before the Liver- 

 pool Medical Society. As I have not been that gentleman's 

 paper, excepting merely so much as is detailed in the critical 

 analysis of books, published in the last number of " Medical 

 and Physical Journal," I am not aware of any new instruc- 

 tions or cautions to render the usual methods more certain ; 

 but the test which I propose as a substitute, appears to be 

 more efficacious, in as much as it produces a more copious 



Vol. 33. Np. 133. May 180Q. Cc precipitate 



