574 



PROFESSOR DITTMAR AND MR JOHN M'ARTHUR ON 



Calculated weight of total mother-liquor = 114-272 grms.; 

 Weight of drawn-oft' liquor analysed, = 99718. Hence, 



Grms. of 



Chloride of Potassium. 



Loose Chlorine. 



Platinum. 



In reagents, 



075518 



1-06538 



0-99086 



In mother-liquor, 



0-06453 



0-40768 



0-07907 



In precipitate, 



0-69065 



0-65770 



0-91179 



Ratios, 



. 149-18 : 



142-063 : 



196-95 



The loose chlorine equals 4-00685 x CI, which, considering the complexity 

 of the method, may be accepted as a sufficient approximation to 4-0000. 



The value Pt, calculated from the loose chlorine, comes to 196 61; cal- 

 culated from the total chlorine, to 196-72. This last number probably is the 

 most exact of the three; but any are considerably above 196. 



The following experiment was made with the view of finding a lower limit 

 for the value of the constant : — 



Experiment VII. 

 9-3125 grms. of chloride of potassium were dissolved in 50 c.c. of water, 

 and mixed with a measured volume of standard platinum solution, containing 

 245 grms. of metal, i.e., only about one-fifth of what the chloride of potassium 

 would demand for its conversion into chloroplatinate. Total volume of mixture 

 = 100 c.c. about. After a night's standing a large precipitate of chloroplatinate 

 had settled out ; it was washed with small successive instalments of water, 

 until the excess of chloride of potassium, by calculation, was reduced to about 

 10 mgs. The washing was then continued with a cold-saturated solution of 

 chloroplatinate of potassium. About 60 c.c. of this solution were used in all ; 

 after it followed two washings with 50 per cent., and at last a few with absolute, 

 alcohol. The precipitate was dried, first for a night over vitriol, and then at 

 100° until constant within 4 to 5 mgs. It was then divided into two approxi- 

 mately equal parts, and both analysed by reduction with hydrogen in the wet 

 way. That combination of the gravimetric with the titrimetric modus, which 

 had served in Experiment VI., was used again. 



Analysis of Part. A. 



Substance analysed, . . . 31626 



Platinum obtained, . . . 12601 



Total chlorine (grav.), . . 1-36772 



(titr.), . . . 1-36730 



(mean), . . 1-36751 



Fixed chlorine (grav.), . . 045921 



(titr.), . . 0-45894 



(mean), . . 045908 



Keferring in both cases to 2KC1 parts, we have — 



Platinum. Total Chlorine. 



A, 194-64 211-227 



B, 194-66 211-158 



Means, 194-65 211192 



B. 



2-6760 grms. 

 1-0672 „ 



1-15775 „ 



1-15750 „ 



1-15763 „ 



0-38894 „ 



0-38855 „ 



0-38875 „ 



Substance = M. 



488-50 



488-12 



488-31 



