20 Mr. Noad on the Action of Nitric Acid on Cymol. 



HO, C,g Hg NO7, rendered it evident, from the mode of its 

 formation, that it must be considered as a substitution pro- 

 duct of a corresponding non-nitrogenous acid, HO, Cig H^ O3, 

 the very acid that is wanting in the toluol series, to the pro- 

 duction of which acid my attention was now particularly di- 

 rected. 



Many attempts were made to oxidize the oil without ha- 

 ving recourse to nitric acid ; long-continued distillations with 

 chromic acid, or with peroxide of manganese and sulphuric 

 acid proved quite ineffectual, but after a great number of 

 tentative operations, I at length succeeded, by the following 

 method, in obtaining the wished-for substance, for which I 

 propose the name of toluyUc acid: — Ordinary nitric acid was 

 diluted Avith about six times its bulk of Mater, and cymol 

 added in the proportion of about 2 oz. of the oil to 1 lb. of 

 the acid ; the mixture was then introduced into a capacious 

 retort and the distillation continued for two or three days ; 

 with acid of this strength there is no fear of a violent action ; 

 the oxidation of the oil proceeds slowly and quietly; it first 

 becomes of a bright blue colour from the absorption of nitric 

 oxide gas, then yellow, and after having been ten or a dozen 

 times poured back into the retort, it begins to change more 

 and more its physical character ; it becomes heavier and more 

 tenacious, and finally sinks to the bottom of the vessel; the 

 process is known to be completed by a portion of the newly- 

 formed acid passing over with the vapour of water, and con- 

 densing in the receiver, and if the whole operation has been 

 successfully conducted, the contents of the retort become 

 nearly solid on cooling from the crystallization of the acid ; 

 the weaker the nitric acid employed, and the longer the time 

 consumed, the whiter and purer is the resulting acid ; if a 

 much stronger acid than that above prescribed be employed, 

 violent action takes place when the boiling-point is reached, 

 nearly the whole of the contents of the retort is projected into 

 the receiver, and the new acid is found at the close of the 

 operation to be contaminated with a considerable quantity of 

 the nitrogenous acid, from which it is impossible afterwards 

 entirely to free it ; even when the operation has been slowly 

 and carefully conducted with a very weak acid, it still con- 

 tains a certain quantity of this acid, as numerous analyses 

 proved, from which it is only to be freed by a series of trou- 

 blesome operations; and it was only after a careful study and 

 comparison of the salts formed by the respective acids that I 

 was enabled to lay down a precise method for their sepai'a- 

 tion. This method is founded on the great solubility of to- 

 luylate of baryta in cold water, and the very sparing solubility 



