ZINC. 149 



In order to adapt these data to the uniform scheme of calculation em- 

 ployed in this work, taking into account their probable error and the 

 probable errors of the antecedent values for K, CI, and Ag, it seems to 

 be best to calculate them back with the atomic weights used by Marignac 

 into the form of the ratio Ag^ : K2 Z nCl^ : : 100 : x. Doing this, and tak- 

 ing each value as many times as there are titrations represented in it — 

 that is, giving the results of a double determination twice the weight of a 

 single one — we have the following series of data for the ratio in question : 



From I 66.090 



T? „ f 66.124 



r rom 2 ■! ^ 



I 66.124 



t:- (66.110 



r rom "^ ' 



( 66.110 



I 66. 1 10 



T.- f66.i< 



r rom 4 ■{ 



l66.i( 



66.104 

 104 

 From 5 66.099 



From6 {^^-'^^ 



I 66.104 



66.129 



[29 



From 8 66. 1 1 3 



T, f 66.1: 



From 7 < 



I 66.1: 



Mean, 66. in, dz .0023 



Hence, from Marignac's work, Ag, : K.ZnCl, : : 100: 66.111, ± .0023, a 

 ratio which can be discussed along with others at the close of this chapter. 

 * During the years between 1883 and 1889, a number of determinations 

 were made of the direct ratio between zinc and hydrogen — that is, 

 weighed quantities of zinc were dissolved in acid, the hydrogen evolved 

 was measured, and from its volume, with Eegnault's data, the weight of 

 H was computed. First in order are Van der Plaats' determinations,* 

 whose results, as given by himself, are subjoined. The weights are 

 reduced to a vacuum. Sulphuric acid was the solvent. 



Zn, grins. H, litres. Zn = 



6.6725 1.(424 65.21 



9.1271 1.5643 65.14 



13.8758 2.3767 65.18 



Mean, 65.177, i .0137 



With the new value for the weight of In^drogen, .089872 gramme per 

 litre, this becomes Zn = 64.980, ± .0137. 



Reynolds and Ramsay made 29 determinations of this ratio. f rejecting, 

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

 experiment the volume of h^^drogen was fixed by the mean of seven or 

 eight readings. The values for Zn are as follows : 



*Compt. Rend., loo, 52. 1SS5. 

 t Journ. Chem. Soc, 51, 854. 18S7. 



