364 Dr. Penny and Mr. W. Wallace on Chloride of Arsenic. 



of the two fluids, containing respectively 18 and 36 equivalents 

 of water, an account of which we reserve for a future commu- 

 nication. 



With respect to the heat evolved on mixing anhydrous chlo- 

 ride and water, we may state that in a particular experiment, in 

 which 117 grains of the former were briskly agitated with a 

 quantity of the latter corresponding to 1 8 equivalents, the tem- 

 perature rose from 60° to 113° F. Then on allowing this mix- 

 ture to cool, and pouring in 18 additional equivalents of water, 

 the temperature increased from 60° to 94°. 



From our experiments on this part of the subject, it appears 

 to us very questionable whether such a hydrate as AsCF, 3H0 

 has been obtained. 



Several experiments were made for the purpose of ascertaining 

 the precise conditions necessary for the production and volatili- 

 zation of the chloride from a heated mixture of arsenious and 

 hydrochloric acids. The most important result was, that chlo- 

 ride of arsenic may be detected in the distillate as soon as hy- 

 di'ochloric acid itself distils ; and further, that this result obtains 

 even with very miniite quantities of arseniovxs acid. With strong 

 hydrochloric acid (containing upwards of 20 per cent, of real 

 acid), anhydrous chloride collects at the bottom of the receiver 

 distinct from the other products. But with acid below 20 per 

 cent., the chloride is found in the distillate in the state of solution. 



It may appear singular that chloride of arsenic should so 

 readily distil over with a liquid which boils at 230° F., when 

 its own boiling-point is 274°. This apparent anomaly, however, 

 is explained by the fact, that the chloride distils freely at a tem- 

 perature very much below its point of ebullitfbn. 



In evidence of the extreme facility with which arsenious acid 

 yields the chloride when heated with hydrochloric acid, we may 

 mention one or two experiments. 



Two-tenths of a grain of arsenious acid were heated in a distil- 

 ling apparatus with 550 grains of hydrochloric acid, specific 

 gravity 1-100; when one-twentieth of the liquid had distilled 

 over, the distillate was tested with sulphuretted hydrogen : a 

 decided precipitate of sulphide of arsenic separated. 



In another experiment one grain of arsenious acid was distilled 

 with 550 grains of the same hydrochloric acid. A piece of 

 copper ribbon placed in the neck of the flask became coated with 

 a crust of metallic arsenic as soon as the liquid began to boil. 

 One-tenth part of the liquid was allowed to distil; and on test- 

 ing one-third of the distillate with sulphuretted hydrogen, the 

 presence of arsenic was clearly indicated. Another third of the 

 distillate was subjected to lieinsch's process, which also gave 

 uneqmvocal proof of the existence of arsenic. The separation of 



