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 

 leaf. 



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 soluble 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 careful review of the methods of detecting foreign leaves shows 

 the microscopic to be the only methods to be relied upon in all cases. 



FOREIGN ASTRINGENTS. 



Catechu. Teas are sometimes treated with this substance to increase 

 their astringency and indicate a greater strength than they naturally 

 possess. 1 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 nitrate should be clear. To a portion of the nitrate 

 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. Einse 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 accord- 

 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 



'Pharm. Centralhalle, 1879, p. 258. 



