TEAS ADULTERATED WITH FOREIGN LEAVES. 



883 



reliance can be placed on the results of such calculations, owing to the 

 sources of error already named. If a tea contains less extract matter 

 than the minima given by G-eisler, the kind of tea being taken into 

 account, it may be placed on the doubtful list, and if all other conditions 

 agree it may be considered to have been adulterated by the addition of 

 spent leaves. In investigating this form of adulteration the appear- 

 ance of the leaf must largely determine the chemist's decision. If the 

 leaves are very much broken, frayed, or partly unrolled, there is evi- 

 dence of spent tea. For the examination, the suspected sample is 

 soaked in water and the softened leaves are unrolled and examined on 

 a glass plate. The following averages of the soluble constituents of 

 genuine teas are given for comparative purposes. The analyses of 

 Geisler are given above, so far as they relate to the extract. 



Table nhowiny the maxima, minium, and mean percentages of the principal soluble con- 

 stituents of tea. 



The differences between the highest and lowest percentages of each 

 constituent are so marked that little possibility of detecting other than 

 exceedingly gross adulteration, by the admixture of spent leaves, is 

 afforded by these analytical data. 



The total ash of genuine teas, according to various authorities, ranges 

 from a little below 5 to nearly 7 per cent, the iron from .08 to .17 per 

 cent, and the silica from .14 to .80. 



FOREIGN LEAVES. 



The addition of foreign leaves is best detected by means of the micro- 

 scope. The leaf of the tea plant is quite characteristic in its venation, 

 serration, and stomata. The veins recurve before reaching the border 

 of the leaf and each forms a loop with its neighbor. The serrations are 

 almost lacking in very delicate leaf buds, but are very distinct in the 

 older leaves. Plates xxxiv and XL have been prepared to illustrate 

 the leaf of the tea plant and other leaves which are said to have been 

 20393 :NO. 13 2 



