190 MR JAMES DEWAR ON THE OXIDATION PRODUCTS OF PICOLINE. 



A. W. Hofmann had successfully employed it to oxidise chinoline into ammonia 

 and oxalic acid. Finding the members of the pyridine series to be easily 

 attacked by this reagent, I commenced a careful examination of the products 

 of the oxidation of picoline, with the object of learning something regarding its 

 internal structure. A preliminary note on the results obtained was communi- 

 cated to the British Association at its Norwich meeting, 1868 (see Report Brit. 

 Assoc. 1868). 



I am indebted to my friend Dr Ronalds of Bonnington for a liberal supply 

 of a quantity of bases that he had carefully prepared, with the object of insti- 

 tuting an investigation into these compounds himself. The crude bases placed 

 in my hands had been repeatedly fractionated on a large scale, and the indi- 

 vidual fractions were thus tolerably pure to begin with. Finding they contained 

 traces of pyrrol and hydrocarbons, I redissolved in acid the fraction boiling 

 from 130° to 160° C, and subsequently treated it in the way recommended by 

 Anderson and Williams to purify these bodies. The mixture of bases thus 

 obtained was subjected to a series of careful fractional distillations. With the 

 object of effecting the best possible separation, T employed the method recom- 

 mended by Warren, and found it admirably suited to effect a comparatively 

 easy separation, so far as fractional distillation can be made to yield a pure 

 product. The bases were transferred to a retort connected with an ascending 

 spiral of copper tube enclosed in a paraffine bath of large dimension, the tem- 

 perature of which was continuously equalised by constant stirring. Five suc- 

 cessive fractionations by this method gave a separation as complete as was 

 necessary for the object I had in view. From the laborious researches of 

 Anderson and Williams, we know that these bases for a large range of tem- 

 perature have the same composition, and that perfectly pure products can be 

 obtained only through the fractional precipitation of the platinum salts. 

 Although I did not make an exhaustive separation by Warren's method, the 

 fractionation was so effective that, by comparing the temperature of the boiling 

 vapour in the retort with the temperature of the paraffine bath throughout the 

 whole course of a distillation, a difference of 10° C. at starting gradually 

 increased to 20°. No fraction that I obtained, separated in this process by a 

 difference of 2° C in the intermediate condenser, had a perfectly constant 

 boiling point. On different occasions fractions separated in this way, boiling 

 between 130° and 140° C, have been employed in the following experiments. 

 Analyses of the platinum salts of portions boiling between those temperatures 

 showed the fractions to be substantially picoline, with a possible trace of 

 lutidine. 



Picoline, as is well known, resists oxidation by the most powerful agents 

 adapted for this purpose, nitric and chromic acids being without visible action, 

 even at high temperatures. Of all oxidising agents, permanganic acid, or its 



