MERCURY. 167 



sulphide was mixed with pure copper and ignited, mercury distilling 

 over and copi)er sulphide remaining behind. Gold leaf was used to 

 retain traces of mercurial vapor, and the weighings were reduced to 

 vacuum : 



34.3568 gim. HgS gave 29.6207 grm. Hg. 86.215 per cent. ^S- 



24.8278 " 21.40295 " 86.206 " 



37 2177 " 32.08416 " S6.207 " 



80.7641 " 69.6372 " 86.223 " 



Mean, 86.2127, dr .0027 



For tlie percentage of mercury in mercuric chloride we have data by 

 Turner, Millon, Svanberg, and Hardin. Turner,* in addition to some 

 precii)itations of mercuric chloride by silver nitrate, gives two experi- 

 ments in which the compound was decomposed by pure stannous 

 chloride, and the mercury thus set free was collected and weighed. The 

 results were as follows : 



44.782 grains Hg = 15.90 giains CI. 73-798 per cent. 



73.09 " 25.97 " 73.784 " 



Mean, 73.791, d= .005 



Millon t purified mercuric chloride by solution in ether and sublima- 

 tion, and then subjected it to distillation with lime. The mercury was 

 collected as in Erdmann and Marchand's experiments. Percentages of 

 metal as follows : 



Svanberg, X following the general method of Erdmann and Marchand, 

 made three distillations of mercuric chloride with lime, and got the 

 following results : 



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



12.529 " 9-2456 " 73-794 



12.6491 " 9-3363 " 73-810 " 



Mean, 73.795, ± .006 



The most recent determinations of the atomic weight of mercury are 

 due to Hardin, § whose methods were entirely electrolytic. First, pure 

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



*Phil. Trans., 1833, 531-535- 

 t Ann. Chim. Phys. (3), 18, 345. 1846. 

 J Journ. fur Prakt. Chem., 45, 472. 1S48. 

 g Journ. Amer. Chem. Soc, 18, 1003. 189 



