568 PROFESSOR DITTMAR AND MR JOHN M'ARTHUR ON 



synthetical data. The platinum was washed, ignited in a small porcelain 

 crucible, and weighed. 



We soon, however, came to discard this method, and to reduce our 

 chloroplatinates in the wet way. The chloroplatinate, after having been dried 

 at a certain temperature and weighed, was placed in an Erlenmeyer flask, 

 along with a sufficient quantity of water to dissolve the chloroplatinate in the 

 heat, the platinum reduced out in the wet way, filtered off, and weighed,* and 

 aliquot parts of the filtrate used for the determination of (in general) the fixed 

 and the total chlorine. 



In the following reports on the several experiments, the symbol A stands 

 for the weight of chloride of potassium used in the synthesis ; P for the 

 approximate weight of platinum used, as chloroplatinic acid, per 2KC1 = 14918 

 parts of chloride of potassium ; M for the exact weight of chloroplatinate 

 which, according to analysis or synthesis, contains 2KC1 parts of chloride of 

 potassium. 



Experiment I. (St Petersburg Metal). 



A = 074grm. (about); P — 2016. Platinum solution poured into that of 

 the chloride of potassium. Total volume of mixture, 40 c.c. The whole was 

 evaporated to 2-3 c.c, and, as no excess of platinum was visible, another 1 c.c. 

 of platinum solution was added (and its water evaporated away) ; hence, 

 finally, P = 209*3. The residue was washed with absolute alcohol (which 

 became distinctly yellow); the chloroplatinate dried at 110°, weighed, and 

 analysed in the dry way. 



The results, referred to 2KC1 parts, were as follows (in the analysis of the 

 precipitate only the platinum was determined) : — 



Platinum. Chloroplatinate, M. 



Synthesis, 19626 491-07 



Analysis of precipitate, 19631 



Hence Pt = 196-29 ; and thence, by calculation, PtCl 6 K 2 = 487*29 = M- 378; 

 hence water, &c, in the chloroplatinate = 0700 per cent. 



Experiment II. (Matthey's Metal). 



0=1-85495; P = 218-4. Platinum poured into potassium salt. Evaporation 

 to about 5 c.c, then addition of absolute alcohol, as in Experiment I. 

 Precipitate washed with absolute alcohol, and dried, first at 110°, then at 

 130°. Reduction by hydrogen effected in the dry way. Combined chloride of 



* Sometimes a film of platinum adheres firmly to the sides of the flask. This is easily recovered 

 by dissolving it in aqua regia, evaporating to dryness in a porcelain crucible, and igniting the residue. 



