330 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



The gases evolved contained only nitrogen and oxygen, in varying pro- 

 portions, which were determined in each case. Uncorrected, Zn = 65.328; 

 corrected, the value ranged between 65.437 and 65.489, in mean, 65.456. 

 Tlie last figure corresponds to 80.358 per cent, of zinc in the oxide, an 

 increase of 0.031. If we assume that the same proportional error existed 

 in all the other experiments upon zinc oxide, the several series may be 

 corrected and combined as follows: 



Jacquelain 80.572, ± .0070 



Erdmann 80.291, ± .0037 



Morse and Burton 80.343, ± .00084 



Morse and Arbuckle 80.358, ± .0011 



General mean 80.349, ± .00065 



Here the two earlier series practically disappear, and the modern de- 

 terminations alone are retained. 



The determinations made by Gladstone and Hibbard ' represent still 

 another process for measuring the atomic weight of zinc. Zinc was dis- 

 solved in a voltameter, and the same current was used to precipitate 

 metallic silver or copper in equivalent amount. Tlie weight of zinc dis- 

 solved, compared with the weight of the other metal thrown down, gives 

 the atomic weight sought for. Two voltameters were used in the experi- 

 ments, giving duplicate estimates for zinc with reference to each weigh- 

 ing of silver or copper. The silver series is as follows, with the ratio 

 2 As: : Zn : : 100 : x in the third column : 



.007: 



Hence Zn = 65.414. 



■ .Juiirn. Cliem. Soc, 55, 443. 1889. 



