130 Mr. H. Caro on the Formation of 



The result was in all cases the same. Not a trace of rosolic 

 acid could be obtained from pure phenylic alcohol, while the 

 formation of rosolates was most decided in the corresponding 

 experiments with the mixture of phenylic and cressylic alcohols. 



Cressylic alcohol yielded not a trace of rosolates upon treat- 

 ment with arsenic acid, or with hydrated oxide of mercury and 

 caustic soda, but the addition of phenol to it gave an imme- 

 diate formation of rosolic acid under these conditions. 



Thus it appears that there is a most striking analogy between 

 the preparation of rosolic acid and rosaniline ; for the latter, as 

 is well known from the beautiful experiments of Hofmann*, is 

 not capable of being formed by the action of oxidizing agents 

 either upon pure aniline or pure toluidine, but is easily obtained 

 from a mixture of the two. 



Passing now to query No. 2. Pure phenol from coal-tar and 

 from salicylic acid was mixed with concentrated sulphuric acid 

 and oxalic acid in the proportions recommended by Kolbe and 

 Schmitt, and maintained at a temperature of 160° C. for 2 J 

 hours. There was very little evolution of gas, and an excellent 

 yield of rosolic acid. 



Kolbe and Schmitfs process, applied to a mixture of phenol 

 and cressol, gave much more gas, and a comparatively poor 

 yield of rosolic acid, whilst with pure cressol there was an abun- 

 dant evolution of gas, and absolutely no production of rosolic acid. 



The formation of rosolic acid from pure phenol was moreover 

 proved by repeating the experiment of Monnet. Two parts of 

 pure phenol, one part of concentrated sulphuric acid, and two 

 parts of iodide of amyle were heated for four hours at 115° to 

 120° C. There was disengagement of iodine, and formation of 

 a notable quantity of rosolic acid. 



A mixture of pure phenol with bromacetic acid, or with gla- 

 cial acid and iodine, or formiates and iodine, gave rosolic acid 

 when heated in a sealed tube., thus confirming the interesting 

 results of Perkin and Duppa. 



Iodoform acts very energetically upon pure phenol (whether 

 prepared from coal-tar or from salicylic acid). 



Iodine and hydroiodic acid are liberated, and a large quantity 

 of rosolic acid is rapidly formed. 



Pure cressylic alcohol and iodoform give not a trace of rosolic 

 acid. 



The next point to be made out, was whether pure aniline, 

 free from toluidine, is capable of giving rosaniline on treatment 

 with reagents containing fatty carbon. For this purpose pure 

 aniline was prepared from indigo, from pure coal-tar benzol, and 

 from benzoic acid benzol. These specimens had been repeatedly 

 * Proc. Roy. Soc. vol. xii. pp. 645-648. 



