JACKSON AND KOCH. — DERIVATIVES OF ORTHOBENZOQUINONE. 207 



Orthoquinone. 



Action of Iodine on the Lead Salt of Pyrocatechine, Preparation of a 



Solution of Orthoquinone. 



To prepare the lead salt of pyrocatechiiie two grams of pyrocate- 

 cliiue dissolved iu 150 c.c. of water were added gradually, with constant 

 stirring, to a boiling solution of 7.5 granas of plunabic acetate in 250 c.c. 

 of water. The precipitated lead salt was allowed to settle, filtered out, 

 and washed five times with hot water. It was then dried at 100°, and 

 finely pulverized. It is not advisable to use more than two grams of 

 pyrocatechine at a time in making the lead salt, as with larger amounts 

 it was found to be hard to wash out all the impurities. 



Ten grams of this lead salt were thoroughly moistened with chlo- 

 roform in a 500 c.c. glass-stoppered Hask. The salt must be absolutely 

 dry, and the chloi'oform free from water and alcohol, as these sub- 

 stances decompose orthoquinone. A boiling solution of five grams of 

 iodine in 200 c.c. of chloroform was then added to the lead salt and 

 the whole shaken well for five to ten minutes ; after which, upon fil- 

 tering through a dry Gooch crucible, a garnet red solution of orthoqui- 

 none was obtained. The amount of iodine used in this experiment is a 

 little more than half that required by the theory (one molecule to each 

 molecule of the lead salt). This large excess of the lead salt was used 

 to avoid as far as possible the presence of iodine in the chloroform 

 solution, and in this we were fairly successful, as a sample of it, when 

 tested with a fresh specimen of the lead salt of pyrocatechine, showed 

 only a trace of plumbic iodide. 



This chloroform solution contained orthobenzoquinone, CeH^Oo 1.2, as 

 is proved by the experiments described later in this paper, and it must 

 have been a nearly pure solution of this body, since the only other sub- 

 stance which could have been present was iodine, and the amount of 

 this was very small, as shown in the preceding paragraph. It had a dark 

 garnet red color, and no odor could be perceived except that of the 

 chloroform. Within an hour from the time of its preparation it began to 

 show signs of alteration by depositing a black precipitate, and after 

 twenty-four to thirty hours all the orthoquinone had disappeared from 

 the solution. We have made numerous attempts to isolate the solid qui- 

 uone from its solution in chloroform, of which the following is a brief 

 summary : Evaporation spontaneously at ordinary temperatures ; evap- 

 oration at— 12° ; evaporation in vacuo of a solution in pure chloroform 

 made from chloral, so as to avoid all traces of alcohol which decomposes 



