ON ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 101 



We have also rephotographed and remeasured the absorption spectra 

 of quinol, resorcinol, and pyrocatechol, which were described by Hartley 

 in 1888.' The agreement between the new and old series of measure- 

 ments is so close, although taken from photographs of the spectra of 

 different preparations and photographed with different instruments, after 

 an interval of fourteen years, that we have not thought it necessary to 

 repeat an account of them in this paper. 



On comparing the mono-, di-, and tri-hydroxy- derivatives it will be 

 observed that while the spectra of the mono- and di- derivatives agree 

 very closely, those of phenol and pyrocatechol being almost identical, the 

 spectra of the tri-hydroxy-derivatives differ from the others in showing 

 less general absorption and in having the absorption band much less 

 distinctly marked. 



Experimental Part, 



Phloroglucinol. — The specimens of phloroglucinol which we examined 

 were obtained from five different sources. 



(1) Specimens prepared from kino were obtained from Merck and from 

 Schuchardt. Both preparations were supplied to us in beautiful scaly 

 crystals, which were practically colourless, and behaved in exactly the 

 same way when heated side by side. They were recrystallised repeatedly 

 from water before being photographed. 



(2) Commercial phloroglucinol, prepared by Schuchardt from resorcinol, 

 was purified by the method given by Will^ and Skraup.^ The purification 

 was completed by boiling with charcoal and crystallising repeatedly from 

 water. The specimen was then tested for diresorcin by dissolving in 

 concentrated sulphuric acid and heating the solution in the water-bath 

 with acetic anhydride. No violet coloration was produced."* All the 

 specimens of commercial phloroglucinol used in the course of this investi- 

 gation were purified by the above method. 



(3) Phloroglucinol was prepared from the tricarboxylic ester by 

 fusion with potassium hydroxide.'^ The specimen obtained by this method 

 crystallised very readily in beautiful plates, which, after being recrystallised 

 several times, had the correct melting-point. 



(4) The method given by Barth and Schreder ^' was employed in the 

 preparation of a fourth specimen. Phenol was melted with six times its 

 weight of sodium hydroxide, and heated until the evolution of hydrogen 

 ceased. The fused mass was acidified with dilute sulphuric acid, and the 

 phloroglucinol extracted with ether. The yield of phloroglucinol was 

 small. So far as we could detect, its properties were identical with those 

 of the other specimens which we examined. It melted at the same tem- 

 perature as the specimens from kino when the determinations were 

 carried out side by side. Its absorption spectra were also identical with 

 those of the specimens from kino. If, as stated by Gautier,^ an isomer of 

 phloroglucinol is obtained by fusing phenol with soda, it is certain that 

 phloroglucinol is likewise one of the products of the reaction. 



(5) A fifth specimen was prepared from maclurin by fusion with 

 potassium hydroxide according to the method described by Hlasiwetz 

 and Pfaundler.* 



» Chem. Soc. Trans., 1888, 53, 641. » Ber., 18, 1323. 



» Monatshefte, 10, 724. * Herzig and Zeisel, Monatshefte, 1890, 11, 421. 



» Baeyer, Beo:, 18, 3454. « ;Ber., 1879, 12, 417. 



' Bull. Soc. Chim., 33, 585. » A)m., 127, 351. 



