CHROMIUM. 249 



From (4) Ag 2 Cr 2 O 7 = 429-177, .2109 



From (10) CrCl 3 = 157.266, dr .01 13 



From (18) Am 2 Cr 2 O 7 250.341, dr .0164 



For the molecular weights of K 2 Cr 2 7 and BaCr0 4 there are two esti- 

 mates each, as given below : 



From (u) K 2 Cr 2 O 7 = 292.433, =b .0189 



From (17) " = 292.143, =b .0224 



General mean K 2 Cr 2 O 7 = 292.311, dr .0144 



From (8) BaCrO 4 = 252.549, ,dr .0966 



From (9) " = 253.054, .0377 



General mean BaCrO 4 252.985, .0351 



Finally, from these molecular weights, eight independent values are 

 obtained for the atomic weight of chromium : 



From Cr 2 O 3 Cr = 5 1 . 796, dr .0039 



From Ag 2 CrO 4 " === 51.698, dr .0191 



From Ag 2 CrO 4 , 4NH 3 " =51.175, .1741 



From Ag 2 Cr 2 O 7 " = 51.904, dr .1055 



From Am 2 Cr 2 O 7 " 51.659, .0085 



From K 2 Cr 2 O 7 "= 51.762, .0102 



From CrCl 3 " =51.729, dr .0183 



From BaCrO 4 " = 53.077, .0362 



General mean Cr = 51.778, dr -0032 



If = 16, Cr = 52.172. 



Rejecting the last of the eight values, that from barium chromate, the 

 mean becomes 



Cr = 51. 767, .0032. 



Even this result is probably too high, for it includes ratios which are 

 certainly erroneous, and which yet exert appreciable weight. From the 

 ratios which are reasonably concordant a better mean is derivable, as 

 follows : 



From (l) Cr 51.741, dr .0065 



From (2).. " =51.734, db .0818 



From (14) " =51.776, .0055 



From (3) and (15) " = 51.698, d= .0191 



From (4) " =51.904, .1055 



From (10) " = 51.729, dr .0183 



From (18) <c = 51.659, .0085 



From (i i) and (17) ' =. 51.762, dr .0102 



General mean Cr = 51.742, dr .0034 



If = 16, this becomes 52.136, a value which is probabty not very 

 far from the truth. 



