198 PROCEEDINGS OF THE AMERICAN ACADEMY. 



nitric acid, whereas the trichlor- or tribrom-homopyrocatechiue gives under 

 the same conditions an orthoquinone ; and also by some experiments 

 undertaken by H. A. Torrey and one of us on the action of hydric diox- 

 ide or electrolytic oxygen on pyrocatecliine, which led to unpromising 

 black products. Accordingly we searched for a method which would 

 produce a quinone without the use of an oxidizing agent, and found one 

 in the action of iodine on the lead salt of the dioxybenzol. After having 

 shown that the method converted liydroquiuone into quinone, we applied 

 it to pyrocatechine ; but our first experiments led to no result, because 

 we used alcohol as our solvent, which attacks the orthoquinone as soon 

 as it is formed. Upon replacing the alcohol by chloroform we succeeded 

 in obtaining a dark garnet red solution, in which the presence of ortho- 

 benzoquinone was established by a number of tests given later in this 

 paper. 



From this solution we nest tried to isolate the solid orthoquinone, but 

 after trying every method we could devise, which gave even a remote 

 promise of success, we have failed to obtain a trace of solid orthoquinone, 

 and are forced to the opinion that it cannot exist in the solid state, or 

 even for any length of time in solution. The products obtained in place 

 of the orthoquinone in every case were a black substance insoluble in 

 chloroform, and a brown substance, or mixture of substances, which dis- 

 solved in chloroform ; this brown product we have not attempted to inves- 

 tigate, but we have studied the black insoluble product, and can give a 

 fairly complete account of its nature in spite of its unmanageable proper- 

 ties. It begins to form in the chloroform solution of the orthoquinone in 

 less than an hour, and is best obtained by allowing the solution to stand in 

 a corked flask for not more than thirty hours. A combustion of the sub- 

 stance gave results corresponding to the formula CigHgOs ; the analysis of 

 a lead salt prepared in a somewhat different way indicated the same for- 

 mula, and this was confirmed by two analyses made by H. A. Torrey of 

 his product from the electrolytic oxidation of pyrocatechine, which seemed 

 to be identical with ours, and by an analysis of the benzoyl derivative of 

 our black substance ; we have, therefore, five analyses of four different 

 samples, all of which agree with each other, and leave no doubt that the 

 substance is a definite compound, and has the formula CioHgOs. This 

 formula indicates that the compound was formed by the union of two 

 molecules of orthoquinone with the introduction of an additional hydroxy! 

 group, a view which is confirmed by the analysis of the lead salt 

 CioHeOsPb, in which there are evidently two benzol rings to each atom 

 of lead. When we consider the manner in which these two benzol rings 



