CRITICAL EXPERIMENTS FOR DETERMINATION OF POTASSIUM, ETC. 617 



A kind of potash-free sea- water was made from pure materials : chloride of 

 sodium, magnesia, and standard solutions of sulphuric and hydrochloric acids. 

 For each analysis a volume corresponding to so and so much average ocean- 

 water was measured out, and the exact weight of a standard solution of chloride 

 of potassium added. The methods were exactly the same as those used in the 

 preceding set. 



Analysis (1) — Finkener's Method ; " Beery stallisation." 



Chloride of potassium used as such, = 148-69 rugs. 



„ „ present in the chloride of sodium used, . = 019 „ 

 Total chloride of potassium, = 148'88 „ = A. 



p = 198-3; px 076084, = 150*87; excess over A = 1-99 mgs., or 1*3 per 

 cent, of A : — partly through compensation of errors. 



The ether-alcohol washings, when worked up for potassium as usual, gave, 



The first washings PtCl 6 K, = 0-36 mg. 



, of KC1. 



The second ,, „ = 0-61 





This analysis was made by means of our present form of the Finkener 

 process ; the foreign bases were converted into sulphates only virtually, i.e., 

 by adding the calculated volume of standard sulphuric acid, &c. 



In the " Challenger " analyses, the first step always was to actually convert 

 all the bases into neutral sulphates, which probably ensures greater constancy 

 in the results. 



Analysis (2) — Finkener 's Method; Sal- Ammoniac Form. 



Total chloride of potassium operated upon (including that of the NaCl), 

 = A = 148-59 mgs. 



Platinum from the chloroplatinate ( + <2?NH 4 C1), = 202-1 =p. ^>x 076084, 

 = 15377; excess over A = 5*18 mgs., or 3*3 per cent of A. Crude KC1 (from 

 nitrate from platinum), = 146*0. Chloroplatinate from the same = 0'4642grm. 

 = 142*17 = " a" mgs. of KC1 ; this is less than A by 6*42 mgs., or 4*3 per cent, 

 of A. 



KC1 recovered (as ultimately PtCl 6 K 2 ) from sal-ammoniac liquors, 

 = 6*54 mgs. = A; from ether-alcohol washings = 0*46 mg. =8. By addition, 

 <z + A = 148*71 mgs. («+a) — A= +0*12 mg., or 0*08 per cent, of A. 



Here again the sal-ammoniac process failed to do justice to itself; in many 

 similar cases we obtained better results, in the sense that far less potassium passed 

 into the sal-ammoniac. The method, unfortunately, is somewhat capricious ; 

 the chloroplatinate does not always stand the sal-ammoniac treatment equally 

 well. To determine small quantities of potassium correctly, the sal-ammoniac 

 liquors must be worked up ; and in no case dares the crude chloride of 



VOL. XXXIII. PART II. 4 X 



