310 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



Other defective series are given to illustrate the partial oxidation of 

 the As^Og by the action of the air. From Kessler's data we get two 

 values for the atomic Aveight of As, thus: 



From KCIO3 series As = 75.225 



From K,CnOT series " = 75.032 



The determinations made by Hibbs ' are based upon an altogether 

 different process from any of the preceding measurements. Sodium 

 pyroarsenate was heated in gaseous hydrochloric acid, yielding sodium 

 chloride. The latter was perfectly white, completely soluble in water, 

 unfused, and absolutely free from arsenic. The vacuum weights are 

 subjoined, witli a column giving the percentage of chloride obtained from 

 the pyroarsenate : 



Na^As^O.;. XaCl. Percentage. 



.02177 .01439 66.100 



.04713 .03115 66.094 



.05795 .03830 66.091 



.40801 .26981 66.128 



.50466 .33345 66.092 



.77538 .51249 66.09& 



.82897 .54791 66.095 



1.19124 .78731 66.092 



1.67545 1.10732 66.091 



3.22637 2.13267 66.101 



Mean, 66.098, ± .0030 



Hence As = 74.895. 



The determinations by Ebaugh " are analogous to those of Hibbs. First, 

 silver arsenate was converted into silver chloride by heating in gaseous 

 hydrochloric acid, and the chloride was afterwards reduced to metal in a 

 stream of hvdrogen. The data obtained are as follows : 



1 Doctoral thesis, T'niversity of Pennsylvania, 1896. Work done under the direction of Professor 

 E. F. Smith. In the fifth experiment the weight of NaCl is printed .33045. This is evidently a 

 misprint, which I have corrected hy comparison with the other data. The rejection of this experi- 

 ment would not affect the final result appreciably. 



^ Doctoral thesis. University of Pennsylvania, 1901. 



