Notes on the Estimation of Potassium as Potassium 

 Platinic Chloride. (Abstract). — By Margaret 

 McCuRDY B. Sc, Dalhousie University, Halifax, N. S. 



(Read 14 December, 1925) 



The separation of potassium from sodium and the subse- 

 quent estimation of the former by precipitation as the platinic 

 chloride has ranked as a standard analytical process for many 

 years. 



According to the method in common use, sodium and pot- 

 assium are first separated from all other constituents as chlorides. 

 They are then converted into chlorplatinates by the addition 

 of hydrochlorplatinic acid in presence of an excess of hydro- 

 chloric acid. The resulting solution is evaporated to dryness 

 on a water bath and the residue treated with absolute alcohol. 

 By these means, sodium platinic chloride is dissolved; the cor- 

 responding potassium salt being insoluble. The potassium 

 chlorplatinate is then separated by filtration and finally dried 

 to constant weight at a temperature not exceeding 100° C. 



In any determination, drying to constant weight at a low 

 temperature is to be avoided if possible, as it not only may 

 introduce a considerable error, but undoubtedly increases the 

 difficulty of manipulation. 



It would be much simpler if it were possible to ignite the 

 precipitate of potassium platinic chloride at a high temperature 

 and from the weight of platinum obtained, calculate the amount 

 of potassium present. 



After a number of preliminary qualitative experiments, 

 the following quantitative determinations were carried out. 



Purified crystals of potassium platinic chloride were care- 

 fully dried and weighed and transferred to a weighed platinum 

 crucible. The crucible and its contents were then ignited to 

 the full heat of a Fisher-Meker burner until constant weight 

 was obtained. The results were as follows: — 



