~ 
¥ MINERAL MATTER IN TEAS. 885 
Theine is detected under the microscope by the appearance of the 
crystals. 
The ash of suspected leaves should be examined for manganese and 
potassium, since both these substances are always present in the tea 
leat. 
A low proportion of soluble ash is an indication of foreign leaves, 
since the ash of leaves suitable for use as an adulterant usually con- 
tains a low percentage of solublé matter as compared with that from 
tea. Facing renders dependence upon the proportion of insoluble ash 
rather uncertain, as this form of adulteration, if excessive, may increase 
the amount of insoluble mineral matter to a considerable extent. 
A eareful review of the methods of detecting foreign leaves shows 
the microscopic to be the only methods to be relied upon in all eases. 
FOREIGN ASTRINGENTS. 
Catechu.—Teas are sometimes treated with this substance to increase 
their astringency and indicate a greater strength than they naturally 
possess.! Hager’s method for the detection of catechu gave very satis- 
factory results in the Department’s investigations. Small quantities of 
the substance can not be detected with certainty. The following is a 
general description of Hager’s method: 
Boil an extract of tea (1 gram per 100 cc. water) with an excess of 
litharge; filter; the filtrate should be clear. To a portion of the filtrate 
add a solution of nitrate of silver. In the presence of catechu a yellow 
flocculent precipitate is formed, which rapidly becomes dark. Under the 
same conditions pure tea gives a slight grayish percipitate of metallic 
silver. The writer prefers a modification of this test, using ferric 
chloride instead of the silver. Rinse a small porcelain dish with a 
dilute solution of ferric chloride; a sufficient quantity of the reagent 
will adhere to the dish. Add the suspected solution, prepared aecord- 
ing to Hager. If catechu is present a characteristic green precipitate 
is formed. 
ADDED MINERAL MATTER. 
Soapstone, gypsum, etc.—These substances, as has been stated, are 
detected by the ordinary methods of qualitative analysis, the particles 
to be examined being separated from the leaves by shaking in a cylinder 
with water. 
Iron salts—Sulphate of iron is said to be occasionally added to a tea 
to deepen the color of the infusion. Iron salts may be separated from 
the leaves or powder by cold dilute acetic acid. This solution is tested 
for iron by the usual qualitative methods. 
Iron.—Metallic iron has been reported as sometimes present as an 
adulterant of teas. Iron may be separated from the finely powdered 
= SS -_—— ED 
1Pharm, Centralhalle, 1879, p. 258, 
