RECOVERY OE THE PLATINUM WASTE 573 



Wolfbauer gives the differences which may arise by computing 

 the potash from its double platino chlorid by the different values 

 -assigned to the atomic weight of platinum. 03 



The common factor used at that time to obtain potassium chlo- 

 rid from potassium platinochlorid was based on the atomic 

 weight 197.18 and is derived from the formula: 



2(39-13 + 35.46) = 149-18 = 



2 X 39-13 + I97.I8 + 6 X 35-46 488.20 

 The variations arising from taking other assigned values for 

 the atomic weight of platinum are shown in the following table : 



The factor 0.3056 was regarded as the best for the computation 

 from potassium platinochlorid and 0.7566 from platinum. It was 

 also suggested that it is better to make the computation from the 

 reduced platinum than from the double salt. Accepting the atom- 

 ic weight of platinum as 194.8, the factor last given in the above 

 table is almost correct. 



485. Recovery of the Platinum Waste and Preparation of the 

 Platinic Chlorid Solution. (i) By reduction in Alkaline Alco- 

 hol. All nitrates containing platinic chlorid, all precipitates of 

 potassium platinochlorid and all residues of metallic platinum 

 should be carefully preserved and the platinum recovered there- 

 from by the following process: The 'platinum residues are placed 

 in a large porcelain dish. Since these residues contain a large 

 amount of alcohol, they should be diluted with about one-third 

 their volume of water, and when boiling treated with some sodium 

 carbonate. The solid potassium platinochlorids should not be ad- 

 -ded until the liquid is boiling, and then only little by little. The 

 heating on the water bath is continued until the liquid floating 

 -over the platinum sponge is quite clear and only slightly yellow. 

 58 Chemiker-Zeitung, 1890, 4 : 1246. 



