G04 



PROFESSOR DITTMAR AND MR JOHN M'ARTHUR ON 



sulphates obtained was " recrystallised" the crystals obtained dissolved, the 

 platinum reduced out by hydrogen and weighed.* 



Results in Grammes. 



Experiment. 



I. KC1 taken, . 



1. 



•75750 



2. 



•75984 



3. 



•75791 



4. 



•76042 



5. 



•75982 



II. Platinum obtained, 



•9959 



•9952 



•9917 



•9945 



•9991 



II. KClif=076117xIL, . 



•75805 



■75752 



•75485 



•75698 



•76048 



Error, i.e., IIT.-L, . 



+ •55 



-2-32 



-3-06 



-3-44 



-0-66 m 



The first alcohol and ether washings from all the five analyses were 

 worked up for potassium by Finkener's method, sal-ammoniac form. Ultimately 

 the KC1 was determined in Fresenius's way, as PtCl 6 K 2 . Found for the five 

 analyses, 1*37 mgs. of KCl. 



The second alcohol and ether washings contained 39*1 mgs. of platinum, 

 equal to 2976 of chloride of potassium, or 595 mgs. per analysis. So much 

 more would have been found (than quantities III.) if the recrystallisation had 

 been omitted. But a determination of the potassium (as Pt) showed that 

 - 26 mg. of KCl per analysis was present in the ether-alcohol liquor. 



Viewing the five analyses as one, we have — 



A. Total chloride of potassium taken, 37955 grms. 



a. KCl lost in the ether-alcohol liquors, .... 00027 „ 

 A = A-a, 37928 „ 



p. Platinum obtained, . 

 A :p = 076270 

 A :p = 076216 

 (p : A ) x (14918 = K 2 C1 2 ) 

 (p : A ) x 



4-9764 



quasi Pt = 19573 

 19560 



II. Set of Experiments. 



This set was carried out before we had come to adopt the recrystallisation 

 modus for purifying the Finkener product. 



It seemed to us at the time that the most exact method of potassium 

 determination would be to eliminate the bulk of the potassium as chloro- 

 platinate by precipitation from purely aqueous solutions, and to utilise the 

 Finkener process only for the recovery of the unprecipitated remnant. 



The substance worked upon was the 95 per cent, salt used in the I. Set. 

 A known weight of chloride of potassium (amounting to about 076 grm.) was 

 dissolved with the necessary impurities, and the solution next evaporated to 

 about 5 c.c. About 1*5 times the calculated minimum of platinum solution 

 was now added to produce some 35 c.c. of mixture, which was allowed to stand 

 over night. The mother-liquor was then decanted off through a small filter, 



* In only one case, No. (4), did the filtrate contain a trace of platinum. It was recovered by H 2 S, the 

 Pt B 2 made into Pt, and its weight (0'4 mg.) added on. 



