94 PROCEEDINGS OP THE AMERICAN ACADEMY 



anhydrides as intermediary products in the synthesis of ketones 

 from benzoic and substituted benzoic acids and hydrocarbons. If 

 anhydrides are formed at all, it is reasonable to suppose that the 

 reaction takes place at a temperature comparatively lower than 

 that required for the ketone condensation; and we find that this 

 is in fact the case. 



I. Action of Phosphorpentoxide upon Benzoic Acid in an 



Excess of Benzol. 



10 grams of benzoic acid, previously melted, pulverized, and thor- 

 oughly dried, were dissolved on the steam bath in about 200 c.c. 

 of dry benzol, 10 grams phosphorpentoxide added to the hot so- 

 lution, and the whole boiled under a reverse condenser for about 

 four hours. The phosphorpentoxide did not appear to dissolve, 

 but settled to the bottom of the flask in the form of an amorphous, 

 gelatinous mass, which became gradually darker, until at the end 

 of the operation, it was nearly black. 



The supernatant benzol solution was of a light amber color. It 

 was filtered hot from the insoluble residue, and, as no precipitate 

 was deposited after standing over night, concentrated to about one 

 third of its volume. On cooling, this solution threw down a co- 

 pious precipitate of fine white needles, which were freed from the 

 benzol mother-liquor by pressing between filter-paper, washed with 

 dilute potash solution to remove possible traces of benzoic acid, and 

 the residue taken up in ether. After one or two washings with 

 water, the ether solution was drawn off, and the residue, after dis- 

 tilling off the ether, dissolved in ligroine. From this it ciystal- 

 lized in fine prismatic needles melting at 41-42°. On analysis the 

 substance gave the following values: — 



0.2153 grm. gave 0.5832 grm. CO, and 0.0903 grm. H 2 0. 



The melting point and composition of the body show it to be 

 without doubt benzoic anhydride, and the study of its properties 

 confirms this conclusion. It consists of fine, prismatic, needle-like 

 forms, easily soluble in alcohol, ether, benzol, chloroform and car- 

 bon disulphide, difficultly in water and in petroleum ether. This 



