GOLD. 233 



This shows plainly that a serious gradual approach to the 

 truth was made with the diminution of the amount of sub- 

 stance used. 



On the whole, the more rational dry way reduction 

 by hydrogen gas gives a mean 2 lower, and deserves the 

 preference. 



A weight of about five grammes of aurate seems most 

 advisable. 



A little further examination of the results of Kriiss, stated 

 on p. 103 of Clarke, shows that the "loss" supposed to be 

 Bra was low, 37 and 31, mean 34 in Nos. 3, 4; and 9 and 18, 

 mean 14, in Nos. 8, 9. The atomic ratio being 0.44 171. 



This points to an incomplete reaction by the H, or to 

 some lack of the formulated constitution in the compound. 

 Nos. 8, 9 show smallest error. 



The aggregate of /oss with Au and Bra in comparison 

 with substance taken, show a gain in Nos. 8 and 9 of resp. 

 6.79 and 2.64 mgr. 



In No. 3 there was a loss of 1.28, in No. 4 a gain of 

 0.56 mgr. 



Here we are evidently touching a very weak spot in this 

 work. 



Taking finally the analytical ratio Ka Br : Au of the 

 residue, and comparing the same to the atomic ratio Ka 

 Br : Au = 119 : 197 = 0.60 406, we find 



Nos. 3489 



405 365 39i 398 



which is i low 41 low 15 low 8 low 



The last two, before recognized as the best determina- 

 tions, give the mean 11.5 low. 



The following are the conclusions that can be drawn 

 from this entire discussion : 



I. While not quite satisfactory in results, this method 



is good. 



II. Needs careful repetition, with moderate amount 



(say 5 gr.), reducing by hydrogen, and 



III. Checking results by ratio Ka Br : Au in residue. 



