ADULTERATION AND DETECTION. 151 



water, but if adulterated, a dark-colored liquor is quickly 

 yielded, which if boiled and let stand until cold will, if 

 spurious, become bitter and almost transparent as it cools, 

 while pure tea under the same conditions assumes a 

 darker color and pleasing flavor. The latter changes 

 arise from the tannin (a natural property in tea) of which 

 artificial tea is entirely devoid and adulterated teas in 

 proportion. Mineral adulterants, however, must be dealt 

 with by the ash-test, which is unerring, spurious leaves 

 by their botanical character and structural marks, 

 deficiency of tannin being invariably an indication of 

 spent or exhausted leaves. 



The part of the tea which we really use being that 

 which passes into the infusion, in other words the 

 Extract of tea it is natural to look to this extract as 

 affording the directest evidence of the quality and 

 genuineness of a sample of tea. The extract may be 

 regarded both quantitively and qualitively, and from the 

 former point of view we are led to the tea-assay or deter- 

 mination of the weight of the tea-extract which a given 

 weight of tea is capable of yielding. 



In Peligot's analyses we find the following determina- 

 tions of the tea-extract the author being quite alive to 

 the importance of such a test : 



Part soluble in boiling water. 



Variety. Ordinary 



Dried Leaf. Conditions. 



Imperial .......... 43.1 396 



Gunpowder, ........ 50.2 49-9 



China, .......... 42.8 39.0 



Japan, .......... 45.8 41.5 



India, .......... 45.4 41.7 



Java ........... 35.2 32.7 



Ceylon, . . ....... 44.4 39.8 



