ATOMIC WEIGHTS 251 



12.048 grm. HgCL gave 8.889 grm. Hg. 73.780 per cent. 



12.529 " 9.2456 " 73.794 



12.G491 " 9.3363 " 73.810 



Mean, 73.795, it .006 

 Hence Hg= 199.706. 



Much more recent determinations of the atomic weight of mercury are 

 due to Hardin/ whose metliods were entirely electrolytic. First, pure 

 mercuric oxide was dissolved in dilute, aqueous potassium cyanide, and 

 electrolyzed in a platinum dish. Six: determinations are published, out 

 of a larger number, but without reduction of the weights to a vacuum. 

 The data, with a percentage column added, are as follows : 



.0003 



Hence Hg= 200.041. 



Various sources of error were detected in these experiments, and the 

 series is therefore rejected by Hardin. It combines with previous series 

 as follows: 



Turner 92.614, ib .0050 



Erdraann and Marchand 92.5996, ± .0015 



Hardin 92.594, ± .0003 



General mean 92.595, ± .0003 



Hardin also studied mercuric chloride, bromide and cyanide, and the 

 direct ratio between mercury and silver, with reduction of weiglits to a 

 vacuum. Electrolysis was conducted in a platinum dish, as usual. With 

 the chloride and bromide, the solutions were mixed with dilute potassium 

 cyanide. The data for the chloride are as follows, the percentage column 

 being added by myself: 



1 Journ. Amer. Chem. Soc, 18, 1003. 1S06. 



