JACKSON AND KOCH. — DERIVATIVES OF ORTHOBENZOQUINONE. 213 



Experiments with the Solution of Orthobenzoquinone. 



Action of Hydrochloric Acid on the Solution of Orthobenzoquinone. 



Dry hydrochloric acid gas was passed through a fresh chloroform 

 solution of orthoquinone (prepared from iodine and the lead salt of py- 

 rocatechine), until it fumed strongly. After filtering out a slight tarry 

 precipitate, a large part of the chloroform was recovered by distillation, 

 and the concentrated solution thus obtained allowed to stand over niaht in 

 an open vessel. The residue, which was usually oily, was heated on the 

 steam-bath to drive off the last traces of the solvent and a slight impurity 

 of iodine, and then extracted with a hot mixture of three parts chloroform 

 with one of ligroin, which left behind a large quantity of a black oil. 

 The solution became milky on standing, and deposited an oily substance, 

 followed, when it had cooled, by the formation of crystals. As soon as 

 these crystals began to appear the clear solution was decanted from the 

 oil and allowed to crystallize in a separate vessel. The residual oils by 

 a similar treatment with chloroform and ligroin yielded an additional 

 amount of the crystals. The crystals were dissolved in benzol, and 

 treated with bone-black, after which they were purified by repeated crys- 

 tallizations from the mixture of chloroform and ligroin. They showed 

 the melting point 84° to 85°, which was not quite constant, indicating 

 that the substance was not perfectly pure ; but in spite of this it was dried 

 in vacuo, and analyzed with the following result : — 



0.2005 gram of the substance gave by the method of Carius 0.1865 gram 

 of argentic chloride. 



Calculated for „ . 



C 6 H 3 C1(0H) 2 . Found - 



Chlorine 24.57 23.00 



This result indicates that the body is monochlorpyrocatechine, but 

 that it contains some pyrocatechine, as would be expected if the reaction 

 ran in the same way as that of hydrochloric acid on parabenzoquinone, 

 since Wichelhaus * has shown that in this case hydroquinone and 

 chlorine are formed in the first instance, and that the substitution com- 

 pounds, which form the final product, are made by the action of the 

 chlorine on the hydroquinone. We have not attempted to purify the 

 chlorpyrocatechine more thoroughly, as much time and labor would be 

 necessary to obtain sufficient material for this purpose, and the forma- 



* Ber. d. chem. Ges., XII. 1504. 



