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 ir0 9 , which is reconverted into 

 gallic acid when boiled with concentrated hydrochloric 

 acid. 



Mono- and Dibromgallic acids, C 7 IFBr0 5 and 

 C 7 H 4 Br*0 5 , $re 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 HX) 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 G-alium 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 



