QUINIC ACID. 361 



do not undergo change, when in a dry condition or 

 when in acid solution in contact with the air, but, 

 when contained in alkaline solution, they absorb oxy- 

 gen rapidly and decompose. Heated with phosphorus 

 oxichloride to 120, it is converted into an amorphous 

 body, digallic acid, C 14 H 10 9 , which is reconverted into 

 gallic acid when boiled with concentrated hydrochloric 

 acid. 



Mono- and Dibromgallic acids, C 7 H 5 Br0 5 and 

 CTMBi^O 5 , are formed by the action of bromine on gal- 

 lic acid at the ordinary temperature. Both compounds 

 consist of colorless crystals, which are but slightly so- 

 luble in cold water, and are not sublimable. 



Rufigallic acid, C 7 ITO 4 + H 2 0, is formed by the 

 slow heating of gallic acid (1 part) with concentrated 

 sulphuric acid (4 parts) to 140 ; and separates in red- 

 dish-brown, granular crystals, when the mass is subse- 

 quently diluted with water. Small, lustrous crystals ; 

 loses its water of crystallization at 120, and sublimes 

 at a higher temperature in the form of cinnabar-red 

 prisms. Soluble in alkalies, forming a red solution, 

 which is decomposed if air is allowed to have access 

 to it ; when treated with baryta-water, it becomes 

 indigo-blue without dissolving. Materials mordanted 

 with alumina salts are colored a beautiful red by it. 

 Fused with potassium hydroxide it yields carbonic 

 acid and a substance called oxyquinone, C 6 H 4 3 , which 

 crystallizes in straw-colored needles. 



The following acid bears a close relation to the pre- 

 ceding acids: 



ftuinic acid, C 7 H 12 6 . Occurs principally in cin- 

 chona barks (also in the false Cinchona nova) ; further, 

 in the bilberry plant, in coffee-beans, in Galium mol- 

 lugo, and probably in small quantity in a great many 

 other plants. Is obtained as a secondary product in 

 the preparation of quinine. The extract, obtained 

 31 



