214 CHEMICAL, MEDICAL AND DIETICAL PROPERTIES. 



fact that Green teas produce these effects, while Black 

 does not, the excessive fermentation to which the latter 

 are subjected in the process of curing, dissipating the vol- 

 atile oil to a greater extent, or, more properly, altering its 

 general character not only in effect but also in flavor. 



Gum or Gluten If it is necessary to estimate the 

 quantity of gum or gluten in tea, as sometimes happens, 

 evaporate an aqueous decoction of the leaves to an 

 extract, and treat the residue with methylated spirit, filter 

 and wash off with hot water, after which evaporate the 

 solution to dryness, next weighing and burning it to an ash 

 and deduct the mineral residue from the original weight 

 of the leaves. Tea extract also yields a large quantity 

 of ammonia when boiled with potash, and it is probable 

 that this character may prove valuable also in testing the 

 genuineness of tea. Tea leaves under an extraordinary 

 amount of ammonia, when submitted to this test, are 

 found to be remarkably rich in nitrogen, the determina- 

 tion of which is also a means of identification. It may 

 also be here remarked that when tea-leaves have been 

 exhausted by infusion, alcohol is still capable of extract- 

 ing a considerable amount of soluble matter. This 

 alcohol extract, when infused in boiling water, furnishes 

 a liquor which smells and tastes strongly of tea, which, 

 were it not for the expense of the solvent and trouble 

 attending its separation, could no doubt be profitably 

 employed. A fixed oil composed of equal parts of oleine 

 and stearine, serving many purposes, medicinal, illumin- 

 ating and others, is extracted from the seeds of the tea- 

 plant in many parts of China and Tartary. The other 

 substances extracted from the tea-leaf consists principally 

 of those which, in various proportions, enter into the com- 

 position of all plants and include a modification of con- 

 stituents analagous to sugar, fat, salts, starch and water. 



