145. HESIN-ACIDS, ETC. 127 



RESINS, ANTHRAQUINONE-DERIVATIVES, BITTER PRINCIPLES, ETC. 



145. Resin-acids and the more important methods for their separa- 

 tion. 



With regard to the coniferous resin-acids, the observations made 

 in 131 may be supplemented by the following: 



Acidic acid 1 occurs in lamellar crystals, softening at 129 and 

 melting at 144, soluble in alcohol and ether, and forming salts 

 with most bases. Prolonged heating converts it into its anhy- 

 dride, which is soluble in absolute alcohol, and was formerly 

 known as pinic acid. The alcoholic solution of this substance 

 yields no crystals on evaporation ; it is gradually reconverted into 

 abietic acid by the continued action of 70 per cent, alcohol. 



Pimaric acid, from Pinus pinaster, forms granular crystalline 

 masses melting at 149, difficultly soluble in cold, but easily in 

 boiling alcohol, and soluble in ether. It resembles abietic acid in 

 most of its properties, but differs in possessing a bitter taste. 



For podocarpic acid see Oudemans ; 2 gardenin, Stenhouse and 

 Groves; 3 phyllic acid, Bougarel. 4 



In isolating resin-acids one of the following methods will be 

 frequently found successful : 



a. Successive treatment with spirit of different strengths, finally 

 adding water and shaking with ether. It will be observed that 

 resin acids are, as a rule, more easily soluble in dilute spirit than 

 resin-anhydrides, wax, etc. It was by this method that I suc- 

 ceeded in isolating mongumic acid from a bark imported from 

 Madagascar. 5 The residue obtained on evaporating the ethereal 

 extract was treated with 85 per cent, spirit, which left a wax 

 undissolved. The spirituous solution was evaporated, and the 



1 Maly considered the acid formerly known as sylvic acid to be abietic ; 

 Duvernoy regards it as a modification of pimaric acid. 



2 Ber. d. d. chem. Ges. vi. 1122 ; Annal. d. Chem. und Pharm. clxx. 213 

 (Journ. Chem. Soc. xxvii. 72). 



3 Annal. d. Chem. und Pharm. cc. 311 (Journ. Chem. Soc. 1878). 



4 Union Pharm. xviii. 262, 1877 (Journ. Chem. Soc. xxxii. 905). A sub- 

 stance similar to that described under the above name is often met with in the 

 analysis of herbaceous and leather}' leaves. It is soluble in boiling alcohol, 

 and separates from such solution, after the wax, on evaporating and cooling. 

 It crystallizes in colourless scales, dissolves with difficulty in water and 

 glycerin, is soluble in ether and chloroform, and also in warm potash, but pre- 

 cipitated by an excess of the latter. 



5 Pharm. Journ. and Trans. [3], ix. 816 (1870). 



