166 THE ATOMIC WEIGHTS. 



MERCURY. 



In dealing with the atomic weight of mercury we may reject the early 

 determinations by Sefstrom* and a large part of the work done by Tur- 

 ner, f The latter chemist, in addition to the data which will be cited 

 below, gives figures to represent the percentage composition of both the 

 chlorides of mercury ; but these results are neither reliable nor in proper 

 shape to be used. 



First in order we may consider the percentage composition of mercuric 

 oxide, as established by Turner and by Erdmann and Marchand. In 

 both investigations the oxide was decomposed by heat, and the mercury 

 was accurately weighed. Gold leaf served to collect the last traces of 

 mercurial vapor. 



Turner gives four estimations. Two represent oxide obtained by the 

 ignition of the nitrate, and two are from commercial oxide. In the first 

 two the oxide still contained traces of nitrate, but hardly in weighable 

 proportions. A comparison of the figures from this source with the others 

 is sufficiently conclusive on this point. The third column represents the 

 percentage of mercury in HgO : 



144 805 grains Hg = 11.54 grains O. 92.619 per cent. 



125.980 " 10.08 " 92.592 " 



I73-5 61 " 13.82 " 92.625 " 



114.294 " 9.101 " 92.620 " 



Mean, 92.614, db .0050 



In the experiments of Erdmann and Marchand J every precaution was 

 taken to ensure accuracy. Their weighings, reduced to a vacuum stand- 

 ard, give the subjoined percentages : 



82.0079 grm. HgO gave 75.9347 grm. Hg. 92.594 per cent. 



51.0320 47.2538 " 92.597 " 



84.4996 " 78.2501 " 92.604 " 



44-6283 " 41-3285 " 92.606 " 



118.4066 " 109.6408 " 92.597 " 



Mean, 92.5996, .0015 



Hardin's determination of the same ratio, being different in character, 

 will be considered later. 



With a view to establishing the atomic weight of sulphur, Erdmann 

 and Marchand also made a series of analyses of pure mercuric sulphide. 

 These data are now best available for discussion under mercury. The 



*Sefstrom. Berz. L,ehrb., 5th ed., 3, 1215. Work done in 1812. 



fPhil. Trans., 1833, 531-535. 



J Journ. fur Prakt. Chem., 31, 395. 1844. 



