CRITICAL EXPERIMENTS FOR DETERMINATION OF POTASSIUM, ETC. 581 



The two mother-liquors derived from the recrystallisations were analysed 

 (by wet-way reduction in hydrogen, &c), so as to determine the absolute 

 quantities of platinum, fixed chlorine, and loose chlorine contained in 

 them. 



The first-mother liquor gave : — 





Platinum. 



Fixed Chlorine. 



Loose Chlorine. 



Absolute weights, 



0-7914 



0-28214 



0-59644 



Relative „ 



. 196-67 



1-9772 x CI 



41798 xCi 



» )> 



. 194-00 



1-951 xCl 



4124 xCl 



The number 196 67 for Pt was chosen at the time, because it resulted from 

 the synthesis of the original chloroplatinate * ; we now utilise it as an upper 

 limit, while 194 is used as a lower limit, for the unknown true "Pt." 

 Either mode of calculation leads to the conclusion that the liquor contained 

 chloroplatinic acid and (really free) hydrochloric acid besides PtCl 6 H 2 . 



These analyses consequently prove, what Seubert only surmised, namely, 

 that a chloroplatinate recrystallised from hot water contains oxygen in place 

 of part of the chlorine of its PtCl 4 , and that the mother-liquor contains 

 hydrochloric acid. 



Before inquiring into the origin of the chloroplatinic acid, let us give the 

 results of the analysis of the second mother-liquor. It contained — 



Platinum. Fixed Chlorine. Loose Chlorine. 



Absolute weights, . 0-5249 0-19199 036097 



Relative „ . 196-67 2-0286 x CI 3-8140 x CI 



. 19400 2-0014 3-7629 x CI 



Either mode of calculation brings out oxychloride-oxygen, and with 

 Pt = 196-67 we obtain, moreover (for so much platinum), 00286 x KC1 of 

 surplus chloride of potassium. But the silver solution used for the determina- 

 tion of the fixed chlorine (in the respective fraction of the filtrate from the 

 platinum), amounted to only 27 3 grms. ; and either of the two numbers for 

 the fixed chlorine (per Pt parts of platinum) must be considered uncertain 

 by about ± 002 of its value (because the weight of the platinum cannot 

 be presumed to be free of error). Correcting it down by 002 of its amount, 

 and reducing to Pt = 195 5 (which number we ultimately came to adopt as the 

 most probable value, vide infra), we have — 



Platinum. Fixed Chlorine. Loose Chlorine. 



195-50 2-0128 x CI 3-7920 x CI 



It really would appear that a little chloride of potassium has been 

 eliminated in the second recrystallisation ; but it is not permissible to draw 

 such a weighty conclusion from a single analysis made on such a small scale. 

 We prefer to look upon the fraction 00128 as resulting from observational 

 errors. 



* And a small slip in a calculation; the correctly calculated value is 196-64. 



