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a 76 M. C. Lea on the Sources of Error in the Employment 
“xcaraanen solutions of picrate a sey gave with 
solution of carbonate ammon’ 
sulphate of rater abundant precipitates. 
carbonate 0 
phosphate of ade, ‘slight precipitate. 
Aqueous solution of picrate of ammonia gave with 
solution of we of ammonia, 
ulphate of ammonia, ~¢ abundant precipitates. 
a row seh of soda, 
“ hosphate of soda, non 
-. Aqueous solution of picrate of magnesia gals with 
solution a carbonate of so 
arbonate of ammonia, 
When the ite, solutions to be tested are otherwise than 
very dilute there is absolutely no difference in the appearance of 
the precipitates. When the amount of precipitate 1s. small, the 
following differences may be observe 
The potash precipitate forms longer eee and when these 
are found only after standing, or when the precipitate is redis- 
solved by heat and allowed to crystallize by slow cooling, they 
exhibit a beautiful play of red and green colors. 
igad soda salt is of a lighter and Weett: yellow than either 
the potash or ammonia salt, Its needles are also shorter than 
those of either of the other compounds, and when the precipitate 
_ has been redissolved by heat, and allowed to crystallize by slow 
_ eooling, they tend to agglomerate themselves together in spheri- 
eal masses. This is a very marke eee and when exhibi- 
ted, is Coy daca but is not always 
e ammonia salt when engtallized in riaiies is very dis- 
tinct in ea e from the potash salt, but when thrown down 
in small ee even by slow erate ess, cannot be distin- 
epee m it with certainty. The prisms are flatter, but these 
ifferences are not apparent in very slender needles. The pay : 
of colors which the ammonia salt exhibits to a less degree than 
ee oueeeoa entirely in the soda salt. 
ty iti eactions ss that yo ee must be 
used 1n e chine picric acid as a test for potas e€ 
tates atove described do not redissolve a an cee ae | 
picrate, or of picric aoe nor is it to be supp that concentra- — 
t abundant precipitates. 
ted alcaline solntians a necessary to cause them—on the con- 
as, in many ¢ te dilute ones are sufficient. To deter 
mine within i nits such reactions are produced, the follow: | 
ing trials were made: 
A. Dilution of the alcaline solutions. Limits ohtaiatd, 
(L) With carbonate of soda, 
