152 THE ATOMIC WEIGHTS. 



i.iooii 1.369S1 80.311 



1. 17038 1.45726 S0.313 



I. 03148 1.28436 80.310 



1.05505 I. 31365 80.308 



Mean, 80.3115, ±00084. 



Combining this mean with the means found by the earlier investigators, 

 we have — 



Jacquelain 80.541, dr .0070 



Erdmann 80.260, zh .0037 



Morse and Burton 80.3115, rt .00084 



General mean 80.317, ±z .0008 



Morse and Burton verified by experiment the stability of oxide of zinc 

 at the temperatures of ignition, and found that it did not dissociate. 

 They also proved the absence of oxides of nitrogen from the zinc oxide. 

 The investigations of Richards and Rogers,* however, have shown that 

 zinc oxide prepared b}^ ignition of the nitrate always carries gaseous 

 occlusions, so that the atomic weight of zinc computed from the data of 

 Morse and Burton is probably too low. But for that objection, their work 

 would leave little to be desired on the score of accuracy. 



The determinations made by Gladstone and Hibbard t 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. The 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 

 Ag,, : Zn : : 100 : x in the third column : 



Zn. Ag. Ratio. 



•7767 2.5589 30.353 



•7758 2.5589 30.318 



•5927 . 1-9551 30.316 



.5924 I -9551 30.300 



.2277 .7517 30.291 



.2281 .7517 30.345 



.7452 2.4588 30.307 



.7475 2.4588 30.401 



.8770 2.9000 30.241 



.8784 2.9000 30.290 



.9341 3-0809 30.319 



.9347 3-0809 30.339 



Mean, 30.318, dz .0077 



* Proc. Amer. Acad., 1893, joo. 

 t Journ. Chem. ,Soc., 55, 443. iS 



