LOSS OF VOLATILE OIL. 29 



and in Gunpowder tea 3*00, and believed that even 

 this quantity was deficient. 



This chemist moreover considers it of importance 

 to determine the quantity of nitrogenised matter 

 contained in tea. He found in 100 parts dried at 

 a temperature of 110°, that Pekoe contained 6*58, 

 and Gunpowder 6*62 of nitrogen ; which is a larger 

 amount than has been found in any vegetable which 

 has bqen examined up to this day. He also found 

 in the exhausted leaves a substance which appeared 

 to have some relation to caseum. From all which 

 circumstances he inferred that tea was a nutrient, 

 as well as a stimulant.* 



The green colouring matter of leaves, Mulder 

 states, depends on a green cerin. The cause of the 

 loss of this green colouring matter of black tea 

 has now been explained ; and the wax after de- 

 composition may be driven off by heat in the pro- 

 cess of roasting. The loss of volatile oil is doubtless 

 due to the same cause. The odour emitted during 

 the process of manipulation, previously to roasting, 

 indicates that this principle is set in action : and 

 as all volatile oils absorb oxygen with avidity on 

 exposure to air, while they deposit a resin, the loss 

 of volatile oil and increase of resin in black tea 

 may be thus accounted for. 



And may not an action of a similar kind account 

 for the black and coal- like appearance found in 



* Monographic du The, par J. G. Houssaye, pp. 100 — 108. 



u 4 



