136 EESINS, BITTER PRINCIPLES, ETC. 



For gr'&nhartin or taignsic acid see Stein and ATnaudson.'^ 

 Pvpitnahok acid also probably belongs to this group.* 

 § 149. Detection of Anthraquinme-darivatives. — To prov6 that 

 these substances, or others that have been separated with- resins, 

 or resins themselves, are entitled to be considered as anthracene- 

 deriviatives, they may be heated dry with zinc dust in a glass tube 

 in the same way as in ultimate, analysis (i.e., a mixture of zinc 

 dust with the substance at the end of the tube, followed by a layer 

 of pure zinc), the products of decomposition being led into a 

 cooled receiver.^ Anthracene and methylanthracene should be 

 specially looked for; both of them are obtained in the form of 

 crystalline sublimates. The former melts at 213°, possesses a 

 blue fluorescence, is insoluble in water, sparingly soluble in 

 alcohol, but more, easily in ether, beiizene and bisulphide of 

 carbon. When dissolved in benzene it forms a compound with 

 picric acid, which separates out in red crystals. The action of 

 bichromate of potash and sulphuric acid convert's it into anthra- 

 quinone. ■ If anthracene alone is obtained, a derivative of that 

 body would be indicated ; methylanthracene alone or together 

 with anthracene would arouse suspicion of the presence of a 

 methylanthracene derivative. .Thie latter possesses, like anthra- 

 cene, a powerful blue fluorescence; it melts at 200°, forms with 

 picric acid a compound crystallizing in dark red needles, yields 

 with bichromate of potash, sulphuric and glacial acetic acids, 

 anthraquinone-earbonic acid,, which is sparingly soluble in excess 

 of, potash and melts at 278°. Methylanthracene is only slightly 

 soluble in ether, alcohol and glacial' acetic acid, but freely in bisul- 

 phide of carbon and benzene. 



§150. HosmatoxijUn, efc.— Treatment with alkali also reveals 

 the presence of heematoxylin ; but it must be observed that this 

 substance can be removed by pure or acidulated water from the 

 evaporation-residue of the ethereal extract (§38).* With alkalies 



' Joum. f..pKikt. Chem. xcix. 1 ; Jahresb. f. Pharm. 165, 1866. 

 ^ Compare Weld, Annal, d. Chem. und Pharm. xcv. 188, 1855 (Amer. 

 Joutn. Phann. xxx. 446). 



* Compare Liebermann and Graehe, Ber d, d. chem. Ges. i. 49, 104, 1868 

 (Journ. Chem. Son. xxv.139). 



* The extraction of heematoxylin with ether free from alcohol -and water is 

 generally incomplete, as it is somewhat sparingly soluble in that menstruum ; a 

 part, therefore, will probably b,e removed on subsequently treating with 

 alcohol. 



