ATOMIC WEIGHTS ;U7 



This figure, reduced to the standard of Berlin's work on the mono- 

 ehromate, becomes 36. 525, ±.034. Berlin's mean was 26. 682, ±.0076. 

 The two means, combined, give a general mean of 26.676, ±.074. 



By Baubigny * we have only three experiments upon the calcination 

 of anhydrous chromic sulphate, as follows: 



1.989 grm. 0^(804)3 gave .7715 grm. Cr.Os. 38.788 per cent. 

 3.958 " 1.535 " 38.782 



2.6052 " 1.0115 " 38.826 



Mean, 38.799, ± .0092 



Hence Cr = 52.14. 



Moberg found for the same ratio the percentage 39.195, ±.028. The 

 general mean of both series, Moberg^s and Baubigny's, is 38. 838, ±.0087. 



In Rawson's work'' ammonium dichromate was the substance studied. 

 Weighed quantities of this salt were dissolved in water, and then reduced 

 by hydrochloric acid and alcohol. After evaporation to dryness the mass 

 was treated with water and ammonia, reevaporated, dried five hours at 

 140°, and finally ignited in a muffle. The residual chromic oxide was 

 bright green, and was tested to verify its purity. Tlie corrected weights 

 are as follows : 



0046 



Hence Cr= 52.15. 



Still later and most elaborate of all, we come to the determinations 

 of the atomic weight of chromium made by Meineke,' who studied the 

 chromate and ammonio-chromate of silver, and also the dichromates of 

 potassium and ammonium. For the latter salt he measured the same 

 ratio that Eawson determined, but by a different method. He procipi- 



1 Compt. Rend., 98, 146. 



= Journ. Chem. Soc, 55, 213. 



:< Ann. Chem., 261, 339. 1891. 



