8 ART. 9. — G. N. POTDAE : ON THE PARTITION 



lead in zinc, and that of zinc in lead were separately esti- 

 mated. For this purpose about 30 grammes of zinc and about 

 45 grammes of lead were kept fused in a tube under exactly 

 similar conditions. After the mass had become cool, the per- 

 centage of lead dissolved in the zinc was determined electrolyt- 

 ically. For the determination of zinc in the lead the latter 

 metal was removed as sulphate, and then the zinc was precipitated 

 as sulphide and finally determined as oxide. From six deter- 

 minations, the mean value found for the solubility of lead in the 

 zinc at about 540°, the temperature of boiling phosphorus penta- 

 sulphide, was 1.35 percent, and for that of zinc in the lead, 

 1.33 percent. 



By the aid of these values it was possible to estimate the 

 amount of the heavier layer which accompanied the lighter layer 

 taken for analysis. The actual amount of the lighter layer 

 analysed being thus known, the percentage of silver in it could 

 be readily calculated. 



To remove the discrepancies in the heavier layer there was 

 no other way than to remove the zinc particles, which was done 

 with a file and a knife. This was tedious work and it took 

 many hours before the contamination was completely removed. 

 The presence of zinc particles was discernible by the different 

 hardness of the two metals, and also by etching with dilute 

 nitric acid, by which the presence of the zinc particles was 

 clearly depicted by the darkening in colour due to the in- 

 numerable small particles of silver disseminated in them. 



The amount of zinc taken for a single fusion was either 20 

 or 30 grammes ; that of lead either 45 or 60 grammes ; Avhile 

 the amount of silver varied from 0.2 to a little above 2 grammes. 

 The results obtained are contained in the following table. 



