112 MCCAY — TRISULPHOXYARSENIC ACID. [April 7, 



acids among the volatile decomposition products. In one case a 

 few grammes of the acid, contained in a miniature retort, were 

 slowly heated in the paraffin bath, the volatile products being con- 

 densed in well-cooled tubes. Two distinct stages in the decompo- 

 sition were observed. Just above the melting point the substance 

 began to boil, giving off pungent-smelling vapors. The aqueous 

 distillate had a strongly acid reaction, and on extracting it with 

 ether and evaporating this solvent, a small quantity of needle-like 

 crystals, having acid properties, was obtained. When the Residue 

 in the retort was heated to about 250°, renewed boiling, and more 

 vigorous than before, took place. The distillate, which was of 

 course separately collected, was oily and viscous, and was found to 

 consist largely of an ether-soluble acid. It has not been prepared 

 in sufficient quantity to permit an analysis. The ammonium salt 

 crystallizes in little prisms, and its solution yields precipitates with 

 calcium, barium, lead and silver salts. The lead salt deposits in 

 beautiful stellated aggregates and seems very characteristic. The 

 study of the decomposition products of dimethyl racemic acid will 

 be continued as soon as enough of the starting material can be 

 procured. 



Central High School^ Philadelphia^ 

 April 1, igo4. 



TRISULPHOXYARSENIC ACID. 



BY LEROY W. MCCAY. 



{Read April 7, 1904.) 



About eighteen years ago, in order to account for the irregu- 

 larities accompanying the interaction of sulphuretted hydrogen and 

 arsenic acid, I assumed the existence of three sulphoxyarsenic acids 

 lying between arsenic and sulpharsenic acid : 



HgAsO^ 



H3ASO3S 



HgAsO.S, 



That the monosulphoxyarsenic acid can exist in the free state I 

 showed in 1886. A few months later Preis, of the University of 



