312 
PHARMA COGNOSY. 
P NO COLOR REACTION WITH SULPHURIC ACID. 
1 SOAPY FEEL. 
199. Talc (Magnesium Silicate). — Rather long irreg- 
ular lustrous and broken crystals. 
2. SOLUBLE IN ACETIC ACID. 
* WITH EFFERVESCENCE. 
200. Calcii Oarbonas Prsecipitatus. — By adding hot 
solution of ammonium oxalate to acetic-acid solution 
on slide, crystals of calcium oxalate are obtained. 
Mounts in glycerin show rosette or cubical crystals 
of a rather uniform size. 
201. Creta Prseparata. — Same treatment as above, but 
calcium-oxalate crystals are triangular and cubical and 
not of uniform size. 
202. Barium Carbonate. — Add sulphuric acid, and in 
glyceriu mount the barium sulphate precipitate is 
bacteria-like. 
** SOLUBLE IN ACETIC ACID WITHOUT EFFERVESCENCE. 
203. Magnesia Ponderosa. — In glycerin mount alone 
small rounded masses are observed frequently grouped 
together; if a few milligrammes be dissolved in citric 
acid on a slide or watch crystal, then a few drops 
(excess) of ammonium hydrate and sodium phosphate 
solution added and stirred vigorously with a glass rod, 
triangular or tetragonal crystals are formed. 
204. Magnesia. — In a glycerin mount the masses 
have the appearance of heavy magnesia, but are larger 
and more transparent. On treatment with citric acid, 
ammonium hydrate and sodium phosphate, the crys- 
tals of ammonium-magnesium phosphate in glycerin 
mount are large, star -shaped, and look like snow- 
crystals. 
