470 On the Destructive Distillation of Animal Substances, 



obvious explanatioD, however, would be to suppose the new bases 

 to be imidogen or nitrile bases, which would enable us to under- 

 stand why they differ from the aniline series, which we know to 

 be amidogen bases. If, however, they belong to either of these 

 classes, they must differ remarkably from any of those hitherto 

 examined, all already formed being extremely unstable, and de- 

 composed even by very feeble affinities, while picoline and its 

 congeners are extremely stable, and resist even the action of 

 nitric acid. Into these points, however, I shall not now enter, 

 but reserve their discussion for a future part of this paper. 



Pyrrol Bases, 



I have already referred, at the commencement of this paper, 

 to another series of bases, to which I have given the provisional 

 name of pyrrol bases, and which distil away from the acid fluid 

 by which the others are retained. They are obtained in the 

 form of an oil, which is transparent and colourless at the moment 

 of distillation, but rapidly acquires first a rose, then a reddish- 

 brown, and finally an almost black colour, and the mixture gives, 

 with hydrochloric acid and a piece of fir-wood, the purple-red 

 colour which Runge describes as characteristic of pyrrol. In 

 fact, I imagined that 1 had at length obtained this substance, 

 which had escaped me in my previous experiments, but I soon 

 found that the product was really a mixture of several different 

 bases. When distilled with the thermometer it began to boil 

 at about 212°, and the temperature gradually rose to above 370°, 

 and during the whole of the distillation pretty large fractions 

 were obtained at every ten degrees, but those between 280° and 

 310° were decidedly larger than the others. These oils were all 

 bases, with a peculiar and disgusting odoui', quite different from, 

 and much more disagreeable than, that of the picoline series of 

 bases. They all acquire colour on standing, although more 

 slowly than the crude oil. These substances dissolve easily in 

 a small quantity of hydrochloric acid, and give, with bichloride 

 of platinum, a precipitate which is at first yellow, but is rapidly 

 converted into a black substance. When dissolved in an excess 

 of acid, and heated along with it, they present a vciy remarkable 

 character ; the solution at a certain temperature becomes filled 

 with red flocks, so abundant and bulky, that, if not too dilute, 

 the fluid becomes perfectly solid, and the vessel can be inverted 

 without anything escaping. The same change takes place, 

 though more slowly, in the cold, and the substance deposited is 

 then of a pale orange-colour, but becomes darker by boiling or 

 exposure to the air. When this substance is collected on a filter, 

 washed, and dried, it forms a reddish-brown and very light and 

 porous mass. It is insoluble in water, acids, and alkalies, but 



