Clifton Golkge Scientific Society. 41 



' Whenever the tea is to be infused for use,' says Tung-po, a 

 Chinese author, ' take water from a running stream, and boil it 

 over a lively fire. It is an old custom to use running water 

 boiled over a lively fire ; that from springs in the hills is said to 

 be the best, and river water the next, while well-water is the 

 worst. A lively fire is a clear and bright charcoal fire. 



' When making an infusion, do not boil the water too hastily, 

 as first it begins to sparkle like crabs' eyes, then somewhat like 

 fishes' eyes, and lastly it boils up like pearls innumerable, spring- 

 ing and waving about. This is the way to boil the water.' 



The chief chemical constituents of tea-leaves may be divided into 

 four, — 



1. A Volatile Oil. 



2. Theine. 



3. Tannin or Tannic Acid. 



4. Gluten. 



THE VOLATILE OIL. 



When commercial tea is distilled with water, there passes over 

 a small quantity of a volatile oil, which possesses the aroma and 

 flavour of the tea to a high degree. 



A hundred pounds of tea yield about one pound of this oil, and 

 to this minute quantity of its volatile ingredient the value of tea 

 in general estimation is in a great measure due. 



This volatile oil does not exist in the natural leaf, but is pro- 

 duced during the process of drying. 



THE THEINE. 



The composition of theine in one hundred parts is as follows : — 

 Carbon, . . 4980 



Nitrogen, . . . 28-83 



Oxygen, . . 16-29 



Hydrogen, . 5 '08 



10000 



It contains, therefore, nearly three-tenths of its weight of nitro- 

 gen, a proportion which exists in only a very small number of 

 known substances. 



Theine (having the formulae CsHioNiOj) is contained in both 

 tea and coffee ; the leaves of the former containing from 2 to 4 

 per cent., the latter rather less than 1 per cent. 



To prepare theine a cold alcoholic infusion of tea-leaves is 

 precipitated by plumbic acetate, for the removal of the tannin 

 which is present. 



