584 PROFESSOR DITTMAR AND MR JOHN M' ARTHUR ON 



and rcsubstitute chlorine for the oxychloride oxygen. This programme was 

 carried out in the following experiments : — 



Experiment X. 



In each of two parallel experiments, I. and II.,* a known weight (about 

 3*8 grms.) of pure chloride of potassium was dissolved in 50 c.c. of water, and 

 the solution mixed with 150 c.c. of chloroplatinic acid solution, made from 

 Matthey's metal by means of the chlorine process. This reagent contained 

 05 grm. of metal per c.c. ; hence the excess of platinum used amounted to 

 about 25 grms. The mixture was evaporated down on a water-bath, as far as 

 possible, on stirring, the residue mixed with a little water, and re-evaporated. 

 After cooling, 25 c.c. of water were added to produce a " ten per cent " platinum 

 solution, and the mixture allowed to stand cold, in the case of" I." for an hour, 

 in the case of " II." for some 12 hours, with occasional stirring. The precipitate 

 was then thrown on a filter, the basin rinsed with 3 c.c. of the 5 per cent, 

 platinum solution, and the precipitate, which was now all on the filter, washed 

 with other 3 c.c. of the same reagent. After the liquor had drained off, the 

 precipitate was washed exhaustively with alcohol of 95 per cent, (by weight). 

 It was then dried in the filter at 100°, the bulk transferred to a tared glass- 

 stoppered cylinder, and in it dried exhaustively at 100° C. The small remnant 

 on the filter was dissolved off with hot water, evaporated in a tared crucible, 

 and weighed by itself. 



The aqueous and alcoholic washings (after removal of the alcohol by 

 distillation from the latter) were reduced with hydrogen in the wet-way, the 

 platinum was filtered off, and the filtrate evaporated to dryness to recover the 

 potassium which had escaped precipitation. This potassium was determined as 

 chloroplatinate (Fresenius' modus). 



The results, so far, were as follows: — 



Chloride of potassium taken, 



„ left unprecipitated, . 



„ in the chloroplatinate, 



Chloroplatinate obtained, .... 

 Hence A : C, 



which numbers seem to show that chloroplatinate " II." having been lixiviated 

 with chloroplatinic acid for 12 hours (instead of for one hour, like " I."), was purer 

 than No. "I." Each of the two chloroplatinatcs was divided into three parts: 

 one (A) for the determination of the platinum and total chlorine, another (B) 

 for the determination of the water by the direct method, and a third (C) for 



* This second experiment was carried out for us by Mr James Robson. 



I 



II. 



3-8062 



3-8061 =A. 



0-0319 



0-0302 



3-7743 



3-7759 =A . 



12-3807 



12-3691 =C. 



0-30485 



0-30525 



