ATOMIC WEIGHTS 227 



With the new value for the weight of liydrogen, 0.89872 gramme per 

 litre, this becomes Zn = 64.980, ±.0137, when H = l. 



Eeynolds and Eamsay made 29 determinations of this ratio,' rejecting, 

 however, all but 5. The weighings were reduced to vacuum, and in each 

 experiment the volume of hydrogen was fixed by the mean of seven or 

 eight readings. The values for Zn are as follows : 



65.5060 

 65.4766 

 65.4450 

 65.5522 

 65.4141 



Mean, 65.4787, ± .0161 



These values were computed with Regnault's data for the weight of H. 

 Corrected by the new value the mean becomes Zn = 65. 280, ±.0161. 



A few determinations by Mallet were made incidentally to his work on 

 the atomic weight of gold, and appear in the same paper." According 

 to these experiments, one gramme of zinc. gives — 



341.85 cc. H., and Zn = 65.158 



341.91 " " 65.146 



341.93 " " 65.143 



342.04 " • " 65.122 



Mean, 65.142, ± .0039 



In this case the Crafts-Regnault weight of H was taken, one litre = 

 .08979 gramme. Corrected, the mean gives Zn = 65.082, ±.0039. 



Two other series of determinations of questionable value remain- to 

 be noticed before leaving the consideration of the direct H : Zn ratio. 

 They represent really the practice work of students, and are interesting 

 as an illustration of the closeness with which such work can be done. 

 The first series was made in the laboratory of the Johns Hopkins Uni- 

 versity, under the direction of Morse and Keiser," and contains 51 deter- 

 minations, as follows : 



Zn = 

 64.68 65.74 65.40 



65.26 64.72 64.80 



65.32 65.26 65.20 



65.20 64.74 64.40 



65.60 64.73 65.00 



64.60 65.10 64.40 



65.00 64.76 65.24 



1 Journ. Chem. Soc, 51, S54. 1887. 

 2Amer. Chem. Journ., 12, 205. 1890. 

 3 Amer. Chem. Journ., 6, 347. 18S4. 



