40 ON ANTIMONIATE OF POTASH AND EARTHS. 
some alkaline sulphuret is poured on them, and an excess 
of muriatic acid is added. 
The primitive form of the crystals is that of an oblique 
rhombic prism. When the crystals are allowed to form 
slowly in a moderately dilute solution of pure sulphate of 
magnesia, they are perfectly developed, and form a sandy 
powder of vitreous lustre, the prismatic form of which can 
easily be detected with the assistance of a good lens. Mag- 
nified 200 times, and with a good light, they appear per- 
fectly transparent, well-defined crystals, which refract the 
light very powerfully. It will always be necessary to at- 
tend carefully to the crystalline form of the antimoniate of 
magnesia, when employing the antimoniate of potash as a 
test for soda; or else to assure oneself of the total absence 
of lime and of magnesia in a liquid by oxalate of potash and 
by basic phosphate of ammonia. 
It should always be borne in mind, that on mixing the 
antimoniate of potash with salts of ammonia, precipitation 
takes place. A solution of the test in 100 parts of water 
gradually affords, with a moderately-dilute solution of sal- 
ammoniac, a considerable flocculent precipitate which most 
probably consists of biantimoniate of ammonia. 
Salts of Alumina. — Antimoniate of potash produces a 
voluminous flocculent precipitate in a solution of potash- 
alum, which re-dissolves to a clear solution in excess of 
alum ; no crystalline deposit is formed, and only after very 
long standing of the liquid are a few flakes apparent at the 
bottom of the test-tube. When a dilute solution of alum 
is mixed with a little antimoniate of potash, the liquid re- 
mains clear, and is not rendered opake even after long 
standing. — Chem. Gaz. from Jircliiv. dtr Pharm. 
