§ 147. P^ONIO-FLUORESCIN, ETC. 131 



of carbonate of soda. The latter may cause a colouration or take 

 up cinnamic acid (detected by the permanganate of potash reaction 

 (§ 26), etc.). For details of the scheme published by Hirschsohn 

 for the identification of the more important resins and gum-resins, 

 reference must be made to the original papers, etc., already quoted. 



§ 147. Fceonio-fluoresc'm. — If agitation with ether (§ 44) removes 

 any substance from solution in caustic alkali it should be ascertained 

 whether the same can be extracted from a solution in a carbonated 

 alkali. It was found that pseonio-fiuorescin^ could be obtained 

 much purer by using a carbonated rather than a caustic alkali, as the 

 latter partially decomposes it, whilst the former does not. Whether 

 the seeds of other plants contain in their testa a body allied to, or 

 identical with, pseonio-fluorescin, and possessing, therefore, a strong 

 fluorescence in ethereal solution, is a matter for investigation. 



Paeonio-fluorescin is sparingly soluble in chloroform, benzene, 

 and cold water (somewhat more freely in warm), but insoluble in 

 petroleum spirit. It is precipitated from a warm (50°) aqueous 

 solution by gelatine, but not by acetate of lead or copper. On 

 boiling with very dilute hydrochloric acid an intense green colour 

 is developed, which can be extracted by agitation with ether, and 

 changes to a reddish-violet in contact with acetate of soda. Its 

 solution in very dilute lime-water, extremely weak ammonia, or 

 €ven chalky spring- water, gradually assumes a fine red colour when 

 exposed to the air. 



§ 148. Anthraquinone-denvatives. — In treating the substances 

 soluble in ether (§§ 36 and 46) with alkaline liquids, any change 

 of colour, especially to red, should be carefully noted. If such 

 is the case there is reason to take into consideration the possible 

 presence of certain anthraquinone derivatives, such as chryso- 

 phanic acid, emodin, frangulic acid, alizarin, purpurin, etc. They 

 are soluble in very dilute alkali, and are precipitated by hydro- 

 chloric acid from the deeply -coloured (generally red) solutions. 

 It frequently happens that these bodies do not occur ready- 

 formed in the fresh substances, or in material that has been care- 

 fully dried, but are present in the form of glucosides- (chrysophan, 

 frangulin, ruberythric acid). 



The following are some of the characteristic properties of the 

 foregoing anthraquinone derivatives. 



1 Archiv d. Pharm. [3], xiv. 412. 



^ Compare my paper on Analyses of Rhubarb ; Pharm. Zeitschr. f . Russland, 



9—2 



