THE SEPARATION AND GRAVIMETRIC ESTIMATION 
OF POTASSIUM. 
S. B. KUZIRIAN. 
The market value of chloroplatinic acid, particularly under 
present conditions, is so high as to warrant a careful search 
for some cheaper reagent for the determination of potassium. 
Serullas 1 , as early as 1831, proposed taking advantage of the 
insolubility of potassium perchlorate in concentrated alcoholic 
solutions and applying it as a reagent for the estimation of 
potassium. Unfortunately his proposal did not receive the at- 
tention it deserved because a convenient method for the prepa- 
ration of perchloric acid had not at that time been worked out. 
Lately, Kreider 2 elaborated a method for the preparation of 
perchloric acid in large enough quantities and in sufficient pur- 
ity to attempt its use as a precipitant for potassium. Follow- 
ing the treatment suggested by Caspari 3 he obtained very satis- 
factory results. 2 
The method was improved and simplified by Willard 4 in 1912, 
enabling one to obtain a very pure product in a comparatively 
short time. This revived old hopes and work was started by 
some of the Station chemists to study its merits as a substitute 
for chloroplatinic acid. 
T. D. Jarrell 5 conducted some co-operative work in collabora- 
tion with other station chemists on some commercial products, 
the object being a comparison of results obtained by the official 
method and the perchlorate method. Ten investigators reported 
varying results on both methods, and the conclusion 6 reached 
was that the perchlorate method in its present form for deter- 
mining potash in mixed fertilizers is very unsatisfactory, con- 
suming too much time, and demanding removal of sulfuric acid 
with barium chloride in case the former is present, and that 
unless sufficient perchloric acid is added to combine with barium 
chloride to form perchlorate, the barium is not washed out from 
the potassium perchlorate precipitate with the alcohol wash, and 
further that potassium perchlorate is somewhat soluble 6 in the 
alcohol wash. 
