•96 Mr. Hume on the Detection of Arsenic. 



more copious than in the other examples ; and, should this 

 be the case, one would be inclined to prefer carbonate of 

 barytes to the other earthv carbonates, when we adopt this 

 mode of detecting arsenic, namely, by native earthy car- 

 bonates. 



In respect to arsenite of lime, the oxalate of ammonia 

 alone miiiht, I should think, serve as a sufficient test, and 



f)rove the existence of arsenic bv first showing that v'i the 

 ime: else, how could nativt carbonate of lime or marble be 

 decomposed under such circumstances? It will serve, how- 

 ever, as a corroborating evidence of the presence of arsenic, 

 and in no small degree add to our knowledge upon this 

 important subject. 



The same observations are applicable to the arsenile of 

 barytes. Here, by means of sulphate of soda, for instance, 

 we can separate the earthv base, which must stand as o7ie 

 proof; and by the nitrate, or the anmioniaco-nitr lie, of 

 silver, for either will succeed, we can discover the arsenic 

 as another, and thus complete the demonstration. 



Having anticipated " Dr. R')get's Reply," which is in- 

 serted in your last number, by my letter to the Editors of the 

 Medical and Physical Journal*, I shall, for the present, 

 abstain from farther animadversions upon that gentleman's 

 *' Case of Recovery from Arsenic," and upon his two " Re- 

 plies," published in consequence of my observations. I 

 shall trust, therefore, that your readers will do equal justice, 

 by permitting me also to refer them to this letter, before 

 they subscribe iheir assent to what | still consider as an in- 

 fringement upon my humble pretensions. 



My three letters are before the public ; they were pub- 

 lished three and two years before the presumed discovery 

 of Dr. Marcet ; they contained the words potass, lime, soda, 

 or any other alkali ; and if these do not comprehend am- 

 monia, and, by a fair induction, the alkaline earths also, I 

 must confess there i? an imperfection in our language 

 which even our best writers do not regard. 



Although it is conlessed, that my discovery of the nitrate 

 of silver as the most effectual test for arsenic, did nor occur 

 to Drs. Marcel and Roget, or to their friends, till their paper 

 was in the press, it is evident that many of my own obser- 

 vations were inserted, with some trifling change indeed in the 

 phraseology, before the " Case of Recovery " was quite 

 nnished and delivered from the hands of ihe printer. Dr. 

 Roget's friends are, it is well known, both numerous and of 

 the highest respectability ; they are men of the first class 



* Medical and Physical Journal for October. 



for 



