SECT. X. BITTER PRINCIPLE. 41 3 



This bitter taste has been thought to be owing 

 to the presence of a peculiar substance, different 

 from every other vegetable substance, and has 

 been distinguished by the name of the Bitter 

 Principle. 



When water has been digested for some time Properties, 

 over Quassia, its colour becomes yellow, and its 

 taste intensely bitter; and if it is evaporated to 

 dryness, it leaves behind a substance of a brownish 

 yellow, with a slight degree of transparency, that 

 continues for a time ductile, but becomes after- 

 wards brittle. This substance Dr. Thomson re- 

 gards as the bitter principle in a state of purity.* 



It is soluble in water and in alcohol ; but the 

 solution is not much affected by re-agents. Nitrate 

 of silver, and acetate of lead, are the only two that 

 occasion a precipitate. 



The Bitter Principle is of great importance, not Uses, 

 only in the practice of medicine, but also in the 

 art of brewing, particularly as it is obtained from 

 the hop, its influence being that of checking fer- 

 mentation, preserving the fermented liquor, and 

 communicating to it a peculiar and agreeable 

 flavour. It appears to consist principally of carbon, 

 hydrogene, and oxygene, with a little nitrogene.-j~ 



* Thomson's Chemistry, vol. iv. p. 242. 

 t Elem, of Agri. CUem. p. 84. 



