145. RESIN-ACIDS, ETC. 129 



course, the others remain in solution ; or finally a mixture may be 

 precipitated, in which, however, a separation may be effected by 

 treatment with solvents or by decomposition with carbonic acid, 

 etc. Hirschsohn met with a case of this description in his examina- 

 tion of galbanum. 1 The resinous portion of the drug was digested 

 with soda, and to the solution chloride of barium was added till 

 no further precipitate was produced. From the dried barium 

 precipitate boiling alcohol dissolved a rather large amount, which 

 separated again on cooling, and contained only T07 per cent, of 

 baryta. This portion must have been carried down either 

 mechanically or in so loose a state of combination that boiling 

 spirit sufficed to effect a decomposition into acid and base. The 

 alcoholic solution contained a second resin-acid, which was partly 

 precipitated on passing carbonic acid through the liquid, and 

 partly, in masses of fibrous crystals resembling asbestos, on the sub- 

 sequent addition of water. Boiling 95 per cent, alcohol extracted 

 it from the dried precipitate. The dilute alcoholic liquid, after 

 treatment with carbonic acid, was acidulated with hydrochloric 

 acid, which threw down a flocculent precipitate, soluble in 

 ammonia. In addition to these three resins a fourth had escaped 

 precipitation with chloride of barium. It could be separated by 

 passing a current of carbonic acid through the alkaline solution. 



In fractionally precipitating with silver or lead salts attention 

 should be directed to the percentage of the metal and the melting 

 point of the resin acid contained in the precipitates. These two 

 points are frequently of service in identifying acids. 



d. The mixed resins may finally be separated by dissolving them 

 in spirit and fractionally precipitating with alcoholic solution of acetate 

 of lead. 



146. Resins and Gum-resins of Commerce. The examination 

 of commercial resins and gum-resins, which generally consist of 

 ethereal oil and various resinous substances frequently accompanied 

 by mucilage, sugar, etc., was at my suggestion undertaken and 

 carried out by Hirschsohn. The following is an abstract of his 

 results : 2 



1 Pharm. Zeitschr. f. Russland, p. 225 et seq., 1875 (Pharm. Journ. and 

 Trans. [3], vii. 369 et seq.). 



2 Pharm. Zeitschr. f. Russland, 225 et seq., 1875 ; 1 et seq., 1877. 'Beit- 

 ra^e zur Chem. der wichtigeren Harze, Gummiharze und Balsame,' Diss. 

 Dorpat, 1877. Archiv d. Pharm. [3], x. 481 et seq. ; xi. 54 et seq. ; xiii. 288 

 et seq. Pharm. Journ. and Trans, viii. 389 et seq. 



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