CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 



HARVARD COLLEGE. 



A REVISION OF THE ATOMIC WEIGHT OF ARSENIC. 



PRELIMINARY PAPER. — THE ANALYSIS OF SILVER 



ARSENATE. 



By Gregory Paul Baxter and Fletcher Barker Coffin. 



Presented December 9, 1908. Received November 26, 1908. 



Below is a summary of the previous work upon the atomic weight 

 of arsenic, 1 the results obtained by the several investigators having 

 been recalculated with the use of the following atomic weights : 2 

 O - 16.000; Ag = 107.880; CI = 35.457; Br = 79.916; S = 32.07 

 K= 39.096; Na = 22.977; Cr = 52.01; Pb = 207.09. 



1816 Thomson, Schweigger Jour., 17, 421, 



2As : As 9 0, 



1818 Berzelius, 

 1845 Pelouze, 

 1855 Kessler, 



1859 Dumas, 



1859 Wallace, 

 1861 Kessler, 

 1896 Hibbs, 



1902 Ebaugh, 



Pogg. Ann., 8, 1, 2As 2 3 : 3S0 2 



Compt. Rend., 20, 1047, AsCL, : 3Ag 

 Pogg. Ann., 95, 204, 3As 2 3 : 2K 2 Cr 2 7 



3As 2 3 : 2KC10 3 

 Ann. Chim. Phys., (3), 55, 174, 



AsCl 3 : 3Ag 

 Phil. Mag., (4), 18, 279, AsBr 3 : 3Ag 

 Pogg. Ann., 113, 140, 3As 2 3 : 2K 2 Cr 2 7 

 Doctoral Thesis, Univ. of Penn., 



Na 4 As 2 7 : 4NaCl 

 Jour. Amer. Chem. Soc, 24, 489, 



Ag s As0 4 : 3AgCl 

 Ag 3 As0 4 : 3Ag 

 Pb 3 (As0 4 )„ : 3PbCl 2 

 Pb 3 (As0 4 ) 2 : 3PbBr, 



76.35 

 75.03 

 74.93 

 74.95 

 75.23 



74.87 

 74.20 

 75.01 



74.88 



75.02 

 74.92 

 75.06 



74.88 



1 Clarke, A Recalculation of the Atomic Weights, Smith. Misc. Coll., 

 Constants of Nature, Part V, p. 213 (1897). For an excellent critical dis- 

 cussion of previous work, by Brauner, see Abegg's Handbuch der anorgani- 

 schen Chemie, 3, (2), 491 (1907). 



2 Richards, Jour. Chim. Phys., 6, 130 (1908). 



