226 SMITHSOXIAX MISCELLANEOUS COLLECTIONS VOL. 54 



A second set of determinations was made by the same analytical 

 method directly npon the recrystallized and carefully di-ied K.ZnCli. 

 Tlie values for Zn are as follows: 



G. Two titrations Zn = 65.28 



7. Two titrations 65.39 



8. One titration 65.32 



In order to a(la])t these data to ihe uniform scheme of calculation em- 

 ployed in this woi'k. takin<i- into account their probable ernn- 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 fonn of the ratio 4Ag: ICZnCl^ : : 100:.'r. 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 liave the following series of data for the ratio in question : 



From 1 66.090 



r G6.124 

 From 2 I 66.124 



r 66.110 

 F^'O^i^ j 66.110 



r 66.104 



I'l'O"!^ I 66.104 



From 5 66.099 



66.104 

 From 6. 



66.104 



f 66.129 

 From? I 66.129 



From 8 66.113 



Mean, 66.111, ± .0023 



Hence, from Marignac's work, 4Ag: K^ZnCl,: : 100 : 66.111,±.0023, a 

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

 It corresponds to Zn = 65.249. 



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 Avas 

 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 Avas the solvent : 



Zn, grm. H, litres. Zn = 



6.6725 1.1424 65.21 



9.1271 1.5643 65.14 



13.8758 2.3767 65.18 



Mean, 65^7^, ± .0137 



1 Compt. Rend.. IM, 52. 1S85. 



