CRITICAL EXPERIMENTS FOR DETERMINATION OF POTASSIUM, ETC. 633 



calculation of the ratios 2KC1 : Pt ; 2KC1 : PtCl 6 K 2 ; 2NH 4 C1 : Pt, in order 

 to obtain the correct factors for the reduction of analytically obtained chloro- 

 platinate. or chloroplatinate-platinum, to chloride of potassium or ammonium, 

 even our number 195*5 is too low ; 196 affords in general a closer approximation. 

 But " Pt," taken in this sense, is no constant at all. Those factors must be 

 determined directly by standard experiments. The results of our own standard 

 experiments are given, and contrasted with theoretically calculated ratios, in 

 the following table. The entries "Ta" refer to Tatlock's method ; the entries 

 "F," to our own modification of Finkener's process as we used it for the 

 analysis of the "95, 82, 33*3 per cent." salt-mixtures; the entries "N" to the 

 customary platinum method for the determination of ammonia. 



Theoretical Factors. 

 Method. Symbols. Values calculated for 



Pt=194-8. Pt = 195-5. Pt = 196. 



Ta. 



2KC1 : PtCl 6 K 2 , 



•30707 



•30665 



•30633 



Ta. 



2KC1 : Pt, 



•76571 



•76307 



•76112 



F. 



2KC1 : Pt, 



•76571 



•76307 



■76112 



N. 



2(NH 4 )C1 : PtCl 6 (NH 4 ) 2 , 



•24123 



•24084 



•24057 



N. 



2(NH 4 )C1 : Pt, . 



•54934 



•54737 



•54598 



D. &M'A.'s 



Empirical 



Factors. 



Note 



•30627 



(1) 



•76016 



(2) 



•76084 





•2389 



(3) 



•5459 



(4) 



Notes. 



( 1 ) Refers to the chloride of potassium in the substance analysed. 



( 2 ) Refers to the chloride of potassium contained in the chloroplatinate precipitate. 



( 3 ) and ( 4 ) both refer to the sal-ammoniac to be determined, not to that contained in the chloroplatinate 

 precipitate. 



11 our 1888 



VOL. XXXIII. PART II. 



4z 



