36 SUBSTANCES SOLÜBLE IN ETHER. 



Paraoxylenzoic Acid melts at 210°, dissolves with difficulty in 

 cold water, and gives, with ferric chloride, a yellow precipitate 

 easily soluble in excess. 



For Orcin and Betaorcin see § 158.^ 



§ 43. Dry Distillation of Resins. — It has already been mentioned 

 in § 27 that the dry distillation of part of the resin may lead to 

 useful results. Besides the umhelliferone mentioned in that 

 section, pyrocatechin (§ 151), pyrogallol, etc., should be borne in 

 mind. The first of these substances is fluorescent, and dissolves 

 in boiling water, alcohol, and ether ; the second strikes a green 

 colour with solutions of ferroso-ferric salts. 



§ 44. Examination of Portion Soluble in AIcoJiol. — The remainder 

 of the mixture of resins extracted ,by ether — that is, the part 

 soluble in alcohol — may be tested as directed in §§ 40 to 43. 

 Acid resins will be found here more frequently than in the 

 portion insoluble in alcohol. If the resin soluble in alcohol 

 dissolves either partially or wholly in an aqueous solution of 

 potash as well, the solution in the latter liquid may be shaken 

 with ether to ascertain if any substance can be removed by that 

 solvent. It was by this means that I isolated pmoniofluorescin 

 from peony-seed (§ 147). Chrysophanic acid and allied substances 

 (§§ 148, 149) should also be tested for, as well as quercitrin, 

 querceiin (§ 152), and the bodies discussed in §§ 150 to 158. 



§ 45. Acids Produced by Action of Alkalies. — Attention must 

 further be paid to the fact that the action of caustic alkalies on 

 certain anhydrides nearly related to the resins — as, for instance, 

 santonin — may result in the formation of alkali salts, which are 

 not of necessity, on the addition of excess of acetic or hydrochloric 

 acid, instantly decomposed Avith reproduction of insoluble anhy- 

 dride. In the case of santonin, santonic acid is liberated on 

 acidulating the alkaline aqueous solution. Any ordinary acid 

 resin mixed with it may be removed by precipitation with hydro- 

 chloric or acetic acid and immediate filtration. The santonin is 

 deposited only after standing several days, but can be extracted 

 at once by shaking with chloroform. A method that I have pro- 

 posed for the estimation of santonin is based upon this fact, and 

 will be described in § 154. 



5^ 4G. Direct Extraction with Ether. — A portion of the powdered 

 material may, Avitliout further treatment, l)e extracted Avith ether, 



^ For ferulic acid compare Jahrb. f. Phanracic, 186G, p. 95. 



