s Ee .s ae 
x» , . 
M. C. Lea on Sources of Error, etc. . 75 
ArT. [X.—WNole on Sources of Error tn the Employment of 
Picrie Acid to detect the Presence of Potash; by M. Canny Lea, 
Philadel phia. 
[Read before the Am. Assoc. for the Adv. of Sci., at Newport, August, 1860.] 
Proric acid enjoys a high reputation as a test for potash. 
operas in its alcoholic solution, or as soda or ammonia salt 
sometimes as magnesia salt, it gives with potash solutions a 
dense valley crystalline precipitate. If the solution containing 
otash be very dilute, the precipitate may not make its appear- 
ance till after some hours repose, and it then forms long delicate 
needles 
ens remarks that this reagent “1s even more sensitive than 
the solution of chlorid of platinum.” In his summing up, he 
observes, that of the various reagents, chlorid of latinum, tar- 
taric acid, picric acid, perchloric “acid, sulphate of alumina and 
hydrofluosilicic acid, ‘the latter is insufficient to distinguish be- 
tween potash an soda; and that the chlorid of platinum and 
I therefore believe that ee remarkable insolubility of ethane 
wise soluble —— es in alcaline solutions has not been” 
before pointed o If an alcoholic solution of picric acid be 
poured into a a of oaresbidls of soda, it occasions an imme~ 
diate dense yellow: precipitate, not to be distinguished in appear~ 
ance from a precipitate of picrate of potash, and liable to be 
mistaken for it with the greatest facility. The picrate of soda 
formed in the case just mentioned is the most soluble of all the 
alcaline picrates, and @ priori we should not expect to find it 
precipitated under these circumstances: an aqueous preven of 
picrate of soda added to one of carbonate of soda a 
cisely the same manner. 
0 ascertain if these reactions were extended to various com- : 
pounds of picric acid, examinations were made which gave with — 
the following results 
Alcoholic solution ‘of picric acid added to 
solution of carbonate of ammonia, ‘gave ai an immediate 
yellow seyatsllies precipitate. : 
‘ _ earbonate of soda gave not so instantaneous spre 
cipitate, but one which after ncn. sean 
even more dense. pet 
Rose, Handbuch der ytischen Chemie, 1F 6-108. 
t Plattner, die Poke dem fstisebes: Bend p- 178. 
