JACKSON AND KOCH. — DERIVATIVES OF ORTHOBENZOQUINONE. 209 



hydroxyl group, but it is obvious that the composition of a body like this, 

 which is amorphous, and has uo definite melting point, can be determined 

 only by the analysis of several samples prepared by different methods. 

 Accordingly we undertook the preparation and analysis of the lead salt, 

 which should be insoluble and stable, if the substance contains two 

 hydroxyls in the ortho position to each other, as would be the case if it 

 is formed from two molecules of orthoquinone. Further, as we thought 

 that the additional hydroxyl indicated by the analysis might have been 

 introduced by the action of the oxygen of the air, we repeated the prep- 

 aration in an atmosphere of carbonic dioxide. The solution of ortho- 

 quinone was made from the lead salt of pyrocatechine and iodine in a 

 flask filled with this gas, and was separated from the plumbic iodide by 

 means of a rose filter with an asbestos film without exposing it to the 

 air. Upon standing over night still in an atmosphere of carbonic dioxide, 

 a black precipitate was formed identical in appearance with that obtained 

 by the ordinary process. This was purified in the way already described, 

 and then converted into its lead salt as follows : 0.3 gram of this black 

 bodv dissolved in 40 c.c. of alcohol was added to a boiling solution of one 

 gram of plumbic acetate in 400 c.c. of water; this large amount of water 

 is necessary to prevent the alcohol from precipitating plumbic acetate, 

 which, becoming imprisoned in the lead salt, could hardly be removed 

 by washing. The jet black lead salt thus obtained was washed five 

 times with hot water, dried at 100°, and analyzed with the following 

 result : — 



0.2352 gram of the salt gave 0.1645 gram of plumbic sulphate. 



Calculated for Calculated for „ , 



C,2H,;0„02l'b. CijHcO.OHOjPb. tound. 



Lead 49.17 47.39 47.76 



This result shows that the oxidizing agent, which introduces the ad- 

 ditional hydroxyl, is not the oxygen of the air, but the orthoquinone 

 itself, and this view is confirmed by the fact that the chloroform solution, 

 from which the black compound has separated, contains brown substances 

 probably formed from the orthoquinone in oxidizing the insoluble prod- 

 uct, but which were so unmanageable that we were unable to determine 

 their composition. 



We would add here two analyses made by H. A. Torrey some years 

 ago in this laboratory with a body agreeing with our black compound in 

 its properties, which he had prepared by the electrolytic oxidation of 

 pyrocatechine. Tiiey gave the following results : — 



VOL. XXXVI. — 14 



