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XXXIX. On Chloro-arsenious Acid, and some of its Comjwunds. 

 ^2/ William Wallace, Ph.D., F.C.S., Glasffow*. 



IN the course of a former series of experiments on the chloride 

 of arsenic f, I observed that arsenious acid dissolved freely 

 in the anhydrous chloride. Believing that a definite combination 

 was formed, I have I'ccently investigated the subject more fully, 

 and have succeeded in preparing a new and highly interesting 

 compound, to which I have given the name of chloro-arsenious 

 acid. My examination of the acid and its compounds is still far 

 from complete ; but I purpose in the mean time to submit a short 

 abstract of my results to the members of the British Association. 



1. Solution of Arsenious Acid in Chloride of Arsenic. 



When chloride of arsenic is heated to gentle ebullition in a 

 small tubulated retort, the beak of which is inclined upwards, 

 and powdered arsenious acid is gradually introduced, the solu- 

 tion of the latter appears to cease when the liquid contains equal 

 equivalents of the two compounds. The readiest method of pre- 

 paring this solution in quantity is to introduce a few ounces of 

 arsenious acid into a flask, and pass hydrochloric acid gas through 

 it until all the arsenious acid disappears. The flask should be 

 agitated occasionally. The action is very violent, and is attended 

 by the elimination of much heat. If the passage of the hy- 

 drochloric acid gas is continued as long as absorption takes place, 

 pure chloride of arsenic is obtained. The nature of the reaction 

 has been fully explained in the paper already referred to. 



2. Chloro-arsenious Acid. 



When the solution of arsenious acid in chloride of arsenic is 

 gradually distilled until it begins to froth up, there separates, on 

 cooling, a pasty, viscid, semi-fluid mass, from which the more 

 liquid portion may be poured off. Analysis gave as follows : — 



Arsenic 1 = 75 59-29 



Chlorine . . 28-11 1=35-5 28-06 



Oxygen 2 = 16 12-65 



126^5 100-00 

 The formula of this compound, therefore, is AsCl" -h 2AsO^ or 



AsClO-, that is, arsenious acid in which one equivalent of oxygen 



is replaced by chlorine. 



Anhydrous chloro-arsenious acid is a viscid fluid or a very soft 



* Communicated by the Author, having been read at the Meeting of 

 the British Association at Leeds, September 24, 1868. 



t " On Chloride of Arsenic," by Pennv and Wallace, Phil. Mag. vol, iv. 

 p. 361. 



