136 XESINS, SITTER PRINCIPLES, ETC. 



For gronhartin or taigusic acid see Stein and Arnaudson. 1 

 Pipitzahoic add also probably belongs to this group. 2 

 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 be heated dry with zinc dust in a glass tube 

 in the same way as in ultimate analysis (Le., 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. 5 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, benzene 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 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 

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

 phide of carbon and benzene. 



150. Hcematoxylin, etc. Treatment with alkali also reveals 

 the presence of haematoxylin ; 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). 4 With alkalies 



1 Journ. f. prakt. Chem. xcix. 1 ; Jahresb. f. Pharm. 165, 1866. 



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

 Journ. Pharm. xxx. 446). 



3 Compare Liebermann und Graebe, Ber d. d. chem, Ges. i. 49, 104, 1868 

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



4 The extraction of haematoxylin with ether free from alcohol and water is 

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

 part, therefore, will probably be removed on subsequently treating with 

 alcohol. 



