CRITICAL EXPERIMENTS FOR DETERMINATION OF POTASSIUM, ETC. 605 



the precipitate washed with small instalments of water until pure by calculation 

 (18 c.c. of water were used in all), then with dilute, and finally with absolute 

 alcohol. The precipitate was dried at 110° and weighed. It was then dissolved 

 in water, the platinum reduced out by hydrogen, and weighed likewise. 



The alcoholic washings were evaporated to dryness, the aqueous liquors 

 added, and after addition of enough of standard sulphuric acid for replacing the 

 CI of the chlorides present by ^S0 4 , the whole evaporated, Finkenerised, 

 and the sulphates removed by sal-ammoniac solution. The resulting chloro- 

 platinate was dissolved in hot water, reduced by hydrogen, the platinum filtered 

 off, and the filtrate next evaporated to dryness, and the residue ignited, to 

 drive off the ammonia-salt. In the ignited salt, the potassium was determined 

 by means of the Fresenius' form of the chloroplatinate process. In some cases 

 the chloroplatinate obtained was reduced in hydrogen (wet way), and the 

 platinum weighed. 



The factors used were — 



For reducing PtCl 6 K 2 to K 2 C1 2 , 0-30435 



Pt 076117 



In Experiments II. to V. chloroplatinic acid made by the chlorine process 

 was used; in Experiment I. a reagent made with aqua regia. 



Results. 



Experiment. 



Chloride of potassium used, . 

 I. Bulk of chloroplatinate, 

 II. K 2 PtCl 6 from liquors, 



III. Total PtCl 6 K 2 , . 



IV. KC1 corresponding, 

 V. Platinum from I., 



VI. „ „ II, 



VII. =V.-r-VI.,. 

 VIII. KC1 corresponding to V. 



IX. „ „ VI. (or 



X. = VIII. + IX., . 



Error in IV. (in mgs.), 

 >, X. „ 

 S0 3 found in I. „ 



1. 



•75380 

 2-3579 

 •1138 

 2-4717 

 •75226 

 •9456 

 •0454 

 •9910 

 •71976 

 •03456 

 •75432 

 -1-54 

 + 0-52 



2. 



•75308 

 2-3776 



•0887 

 2-4663 



•75062 



•9529 



3. 



•75497 

 2-3824 



•0926 

 2-4750 



•75326 



•9549 



•72684 



(•02818) 



(•75502) 



-1-71 



+ 0-05 



0-75 



4. 



•75467 

 2-3528 

 •1202 

 2-4730 

 •75266 

 •9430 

 •0487 

 •9917 

 •71778 

 •03707 

 •75485 

 -2-01 

 + 018 



72532 



II), -03456 (-02700) 



(-75232) 



-2-46 



-0-76 



0-51 



Total chloroplatinate produced, i.e. (I. + II), 



Total chloride of potassium employed, 



Hence chloride of potassium per unit of chloroplatinate dried at 



110° C, 



Total platinum obtained in experiments 1, 4, and 5, . 

 Total chloride of potassium for experiments 1, 4, and 5, . 

 Hence A :p = 0-76087 

 and (p : A) x K 2 C1 2 = 196-06. 



•75390 grm. 



2-3569 „ 



•1190 „ 



2-4759 „ 



•75354 „ 



•9423 „ 



•0484 „ 



•9907 „ 



•71725 „ 



•03684 „ 



•75409 „ 

 -0-36 

 + 019 



mg. 



12-3619 grms. 



3-7704 „ 



0-30500 „ 

 = 2-9734 =p. 

 = 2-2624 =A. 



