586 PROFESSOR ANDERSON ON THE PRODUCTS OF THE 



Pyrrol. 



Reference has frequently been made throughout the course of this investiga- 

 tion to the substance discovered by Runge* in coal-tar, and called by him pyrrol. 

 This substance he described as a gas, although he appears never to have prepared 

 it in a pure state, but simply to have obtained its very singular reaction with 

 fir-wood ; and he mentions that it occurs in very small quantity, and accom- 

 panies the ammonia produced during destructive distillation. In the second part 

 of this paper, when describing the preparation of the bases from crude bone oil, 

 it was stated that the acid solution afforded on distillation a quantity of an oil 

 possessing in a high degree the characteristic reaction of pyrrol, and which was 

 decomposed when boiled with moderately concentrated acids, with the precipita- 

 tion of a red resinous matter, while the fluid was found to contain different num- 

 bers of the pyridine series of bases. From these facts I was led to infer that this 

 oil contained a series of bases in which pyridine and its homologues were coupled 

 with some substance which was separated by acids, and converted into the red 

 resin, — an opinion which further experiment has entirely refuted. 



The oil collected during the distillation of the acid solution of the crude 

 pyridine bases, had a peculiarly fetid and disagreeable smell, and was at first 

 colourless, but soon acquired a reddish colour, and after a few days became 

 nearly black. When freed from water it began to distil about 250°, and a ther- 

 mometer placed in the tubulature of the retort gradually rose as the distillation 

 proceeded, until at length it reached nearly 400°. The greater proportion of the 

 oil passed between 280° and 310°, but large fractions were obtained at much 

 higher temperatures. All the fractions had a characteristic smell different from 

 that of the pyridine bases, and gave instantaneously the reaction of pyrrol. When 

 treated with acids, the red resinous matter was deposited, and the filtered fluid, 

 on treatment with potash, evolved the smell of different members of the pyridine 

 series, according to the boiling point of the fraction selected for the experiment. 

 The oil containing pyrrol was now subjected to a systematic fractionation ; and it 

 was found, after several rectifications, to manifest a decided tendency to concen- 

 trate itself towards a fixed point, the fractions collected between 270° and 280°, and 

 280° and 290°, greatly exceeding the others in bulk. The oil obtained at these tem- 

 peratures was perfectly transparent and colourless when freshly distilled, but 

 soon acquired a brown colour, though much less rapidly than the crude sub- 

 stance. When agitated with very dilute acids, a certain portion of it immediately 

 dissolved, but the remainder was very slowly acted upon, and required a large 

 excess of acid, and much shaking, in order to make it dissolve, which, however, 

 it eventually did completely. This fact appearing to indicate that the substance 



* Poggendorf's Annalen, vols. xxxi. and xxxii. 



