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, Cl, and Ag, it seems to 

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

 into the form of the ratio A 4 : K 2 Z nd 4 : : 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 1 ................................... 66.090 



From 2.. 



66.124 



f 66. no 

 From 3 .................................... { 



l66.no 



f 66.104 

 P rom 4 .................................... < 



166.104 



From 5 .................................... 66.099 



f 66.104 

 P rom 6 .................................... 4 



(. 66.104 



f 66.129 

 From 7 ................................... \ 



166.129 



From 8 ................................... 66.113 



Mean, 66.111, d= .0023 



Hence, from Marignac's work, Ag 4 : K 2 ZnCl 4 : : 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 Regnault's data, the weight of 

 H was computed. First in order are Van der Plaats' determi nations j* 

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

 reduced to a vacuum. Sulphuric acid was the solvent. 



Zn, grms. H, litres. Zn = 



6.6725 1.1424 65.21 



9.1271 i.5 6 43 65.14 



13.8758 2.3767 65.18 



Mean, 65.177, .0137 



With the new value for the weight of hydrogen, .089872 gramme per 

 litre, this becomes Zn = 64.980, db .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 hydrogen was fixed by the mean of seven or 

 eight readings. The values for Zn are as follows : 



* Compt. Rend., 100, 52. 1885. 

 f Journ. Chem. Soc., 51, 854. 1887. 



