OF SILVER BETWEEN ZINC AND LEAD. 



ordinary test-tube. This tube, being attached to an asbestos 

 cardboard, was suspended in a larger vessel, for which the card- 

 board served as a lid. For this outer vessel a very big test-tube 

 about 20 cm. in height and 4.5 cm. in diameter was found most 

 suitable. In order to obtain a constant temperature phosphorus 

 pentasulphide was kept boiling in this vessel. 



Of the three metals used, the lead and the silver were 

 commercially pure, the metallic impurities contained in them 

 being in such minute quantities as not to affect the determination 

 of the partition coefficient to any appreciable extent ; the zinc 

 was chemically pure. 



The method of procedure was as follows. Zinc rods and 

 pieces of lead were first filed to remove any oxide that might 

 have been formed on them. The lead was melted in a porcelain 

 crucible and the silver added to it. When the 

 latter was completely dissolved, the mass was 

 allowed to solidify, and cut in pieces of proper 

 z:zi size. These together with pieces of zinc were 

 introduced into the melting tube, care being 

 taken to have the zinc pieces at the bottom. 

 The tube was then fitted in the outer vessel 

 in which powdered phosphorus pentasulphide 

 had been put. At first a rapid current of 

 carbon dioxide gas, purified and dried by being 

 passed through sodium bicarbonate solution and 

 concentrated sulphuric acid, was introduced into 

 the inner tube to displace all the air, and then 

 a very slow and steady current of the gas was 

 kept up all through the experiment in order to reduce the loss 

 of the metals by oxidation. The outer vessel was heated by the 



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