136 BE SINS, BITTE B BBINCIPLES, ETC. 



For gwnJiartin or taigtisic acid see Stein and Arnaudson.^ 

 Pipitzaliok acid also probably belongs to this group. ^ 

 § 149. Detection of Anthraquinone-derivatives. — To prove that 

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

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

 derivatives, they may he heated dry with zinc dust in a glass tube 

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

 dust Avith 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, sjiaringly soluble in 

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

 carbon. When dissolved in benzene it forms a compouijd with 

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

 bichromate of potash and sulphuric acid converts 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. The 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-carbonic acid, which is sparingly soluble in excess 

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

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

 ]3hide of carbon and benzene. 



§ 150. Ilcematoxijlin, etc. — Treatment with alkali also reveals 

 the presence of ha^matoxylin ; but it must be observed that this 

 substance can be removed by pure or acidulated Avater from the 

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



^ Journ. f. prakt. Chem. xcix. 1 ; .Tahresb. f. Pharm. 1G5, 1866. 



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

 Journ. Pharm, xxx. 446). 



' Compare Liobermann und Graebe, Ber d. d. chem. Ges. i. 49, 104, 1868 

 (Journ. Chem. Soc. xxv, 139). 



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

 generally incf)mpk'te, as it is somewhat sjiaringly soluble in that menstruum ; a 

 part, therefore, will iirobal)ly Ijc removed on subsequently treating with 

 alcohol. 



