Dr. Stenhouse on Theine and its Preparation. 427 



all the colouring matters it contains. It is filtered while hot, 

 and the clear liquor is evaporated to dryness. It forms a dark 

 yellowish mass, which is to be intimately mixed with a quan- 

 tity of sand, and introduced into Dr. Mohr's subliming appa- 

 ratus. This should then be set upon a sand-bath, or still 

 better on a metallic bath, and a moderate heat applied to it 

 for 10 or 12 hours. The theine sublimes in beautifully white, 

 anhydrous crystals, and is deposited upon the paper diaphragm 

 which runs across the apparatus. The only thing to be ob- 

 served is, that the temperature should never rise too high, as 

 the more slowly the operation is conducted, the finer are the 

 crystals and the greater is their quantity. The following are 

 the results obtained by this process in four different trials. 



I. One pound of green Hyson tea gave 72 grains of per- 

 fectly white theine, and 2 grains which were slightly coloured, 

 in all 74 grains =1*05 per cent. 



II. 8 oz. of black Congo tea gave 34*5 grains pure theine, 

 and 1*5 grain impure, in all 36 grains = 1*02 per cent. 



III. 6 oz. black Assam tea yielded 36 grains theine= 1*37 

 per cent. 



IV. 1 lb. of a cheap green tea called Twankay, gave 

 69 grains = 0*98 per cent. This last was sublimed too quickly, 

 or it would probably have given a little more theine. 



We have four determinations of the theine in different 

 specimens of tea by Mulder. He found in Chinese Hyson 0*43 

 per cent, theine, in congo 0'46 per cent, in Japanese Hyson 

 0*60 per cent., and in Japanese Congo 0*65 per cent. 



Mulder's process consisted in boiling the filtered decoction 

 of the tea with magnesia, evaporating to dryness and then 

 dissolving out the theine from the dry mass with aether. I 

 have repeatedly tried his process, but found it very trouble- 

 some and unproductive ; besides, the theine always requires 

 more than one crystallization to render it quite pure, and the 

 high price of aether, in Great Britain, at least, is a very serious 

 inconvenience. It is to the presence of theine, I believe, that 

 the bitter taste of tea is chiefly owing, and a tolerably correct 

 idea of the quantity of theine in any specimen of tea may be 

 formed from the degree of bitterness which it exhibits. The 

 Assam tea, which yielded such a large proportion of theine, 

 was remarkably bitter, but it appeared rather deficient in es- 

 sential oil. 



Theine may also easily be made from coffee, by a slight 

 alteration of the method just described; the coffee beans 

 should not be roasted, as this would drive off much of the 

 theine, but only slightly dried, and then ground or pounded, 

 and repeatedly boiled with water till exhausted. The filtered 



