Test for Arsenic. — Northern Expedition. 149 



TEST FOR ARSENIC. 



Mr. Hume of Long Acre, who more than twenty-eight years 

 ago directed the public attention to the excellence of silver as a 

 test for aiscnic, and has ever since continued improving the dis- 

 covery bv a variety of relative experiments, has been again called 

 forth in defence of the validity of the test, in consequence of an 

 opinion thrown out by several professional nien^ on the occasion 

 of a recent trial at Launceston for murder by poison — that no- 

 thing short of the revivification of the arsenic into its metallic 

 form can or ought to be accepted as evidence in cases of medical 

 jurisprudence In a paper which Mr. Hume has just published 

 on the subject, he combats this theory in a very able manner, and 

 refers in Ins support to some of the principal parts of his former 

 comnuniications to the public. The first public communication 

 in which he announced silver to be the most effectual test for de- 

 tecting arsenic, appeared in the Philosophical Magazine for May 

 1S0;>. As it is evident that the operation must be by doiible che- 

 mical affinity or elective attraction, Mr. H. then advised subcar- 

 bonate of soda to be joined to the arsenic, and nitric acid to the 

 silver. In another communication to the Phil. Mag. of August 

 1812, Mr Hume detailed a variety of experiments which he had 

 made with ammonia, from which he was led to form a triple salt, 

 either with silver or copper and that alkali, which he considered 

 to be a test of most valuable acquisition to analytical chemistry, 

 since by its assistance we are now able to ascertain the precise 

 quantum of alkali required, which could not otherwise be readily 

 obtained. This test possesses also another property; — it does not 

 affect phosphate of soda : other phosphates it is true exist in the 

 human system, especially in the urine; but there seems little to 

 fear from the presence of any soluble phosphate whatever in fluids 

 mixed with extraneous matters ejected from the human stomach. 

 The last paper on the subject by Mr. Hume, appeared in the 

 Phil. Mag. of October 1812, in which he added an account of a 

 variety of other experiments which he had made, in order to as- 

 certain the comparative eligibility of magnesia, barytes, lime, 

 and other earths, as tests for arsenic. 



NORTHERN EXPEDITION. 



The arrangements for the vessels about to explore the Arctic Re- 

 gions are now nearly completed, and it is expected they will leave 

 the river about the 24th of March. Every precaution has been 

 taken for the general comfort of the crews; fixed bed places are 

 fitted, with sliding doors, for the men to sleep in, housings to 

 form roofs over the ships in the event of being frozen in, a liberal 

 supply of vegetables, and a proportion of six months beef, slightly 

 coined, with --omc preserved meat, will be supplied. 



K ti The 



