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



strong flame of a ring burner, the upper part of the tube being 

 covered with asbestos paper to diminish the loss of heat by 

 radiation. The height of the flame was so regulated that the 

 dark brown vapour of the phosphorus pentasulphide reached to 

 within a few centimeters of the top of the vessel and remained 

 nearly constant the whole time. The metals in the inner tube 

 lay well below the upper limit of the vapour so that all danger 

 of cooling from above was excluded. Within a short time the 

 metals became melted, and the mass was thoroughly stirred three 

 times at intervals of five minutes. For this purpose a thin glass 

 rod bent at one end was used. Finally the mass was kept in 

 the melted condition for about five hours and a half, in order 

 to secure a complete separation of the two layers. At the end 

 of this period the flame was removed and the whole allowed to 

 cool as rapidly as possible, so that the layers might not be 

 disturbed and the alloys might solidify without a redistribution 

 of the components. 



The solidified lump of the metals consisted of two layers, 

 the lighter in which zinc predominated and the heavier in which 

 lead preponderated, each containing a small percentage of the 

 other metal and the silver being unequally divided between them. 

 These layers were cut in pieces with a saw parallel to the line 

 of demarcation and the silver contents of the pieces were sepa- 

 rately determined, Volhard's method of titration being employed. 

 For the pieces from the lighter layer, which contained the 

 greater portion of the silver, a decinormal solution of ammonium 

 thiocyanate was used ; while for the pieces from the heavier 

 layer a twentieth to fiftieth normal solution was employed ac- 

 cording to the amount of the silver contents. 



The calculation of the ratio of the silver contents of the 



