[ 361 ] 



LVII. Notice on Chloride of Arsenic. 

 By Dr. Penny mid William Wallace^ Esq.^ 



SOME time since we were led to undertake a series of expe- 

 riments on the properties and composition of the chloride 

 of arsenic, with the view partly of testing the accuracy of the 

 researches that have been made for determining the equivalent 

 of arsenic, and partly of ascertaining the availability of this sub- 

 stance for the separation of arsenic from other metals, as well as 

 from organic matters in toxicological inquiries. The publication 

 of some of our results has been anticipated by Dr. FytVs excel- 

 lent paper " On the Detection of Arsenic," published in the Phi- 

 losophical Magazine for December 1851. There are, however, 

 several points connected with the chemical history of this inter- 

 esting compound which have not yet been noticed, and we 

 therefore trust that a brief statement of our investigations may 

 not be altogether unacceptable to the Philosophical Society of 

 Glasgow. 



Gmehn's Handbook of Chemistry contains a fair abstract of 

 the several researches that have been made upon the properties 

 of chloride of arsenic, with the results of its analysis by Dr. J. 

 Davy. It has been analysed more recently by Pelouze, who 

 employed it for the determination of the atomic weight of me- 

 tallic arsenic f. Its production in medico-legal investigations has 

 been incidentally noticed by several authorities ; but its invari- 

 able formation by heat from arsenious acid in presence of hydro- 

 chloric acid has, we think, been frequently overlooked ; and in 

 certain processes recommended for the separation of arsenic from 

 organic matters, its ready volatility would unquestionably be 

 very liable to occasion a loss of a portion of the metal. 



To these points our attention has been particularly directed, 

 and our results fully confirm the several statements made by 

 Dr. Fyfe in the paper referred to. Before giving these results, 

 however, we shall describe the processes by which we obtained 

 anhydrous chloride in a state of purity, and the new method by 

 which we estimated the proportion of arsenic existing in it. 



In one process for its preparation, powdered arsenious acid 

 was put into a report with a considerable quantity of concen- 

 trated hydrochloric acid, and the mixture distilled. Anhydrous 

 chloride and a solution of chloride of arsenic in hydrochloric 

 acid soon collected in the receiver. The former was found at 

 the bottom as a dense oily liquid, and the other products floated 

 above. The anhydrous chloride may be easily separated with a 



• Communicated by the Authors, having been read at tlie Meeting of the 

 PhiloKophical Society of Glasgow, January 7. 1852. 

 t Comptes Rendus, vol. xx. p. 1047. 



