--=- — ve 

DESTRUCTIVE DISTILLATION OF ANIMAL SUBSTANCES. 259 
which would enable us to understand 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 decomposed 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 fiuid 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 Runee describes as characteristic. of 
pyrrol. In fact, I imagined that I 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 thermo- 
meter 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 
_eyery ten degrees, but those between 280° and 310° were decidedly larger than 
the others. These oils were all bases, with a peculiar and disgusting odour, 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 very 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 soluble in 
alcohol, and the solution on evaporation leayes a dark resinous mass. When 
subjected to dry distillation, it leaves a bulky charcoal, while an exceedingly dis- 
gusting oil distils. 
The acid fluid which has been separated from this substance by filtration, 
when supersaturated by an alkali, evolves the odour of the bases of the picoline 
VOL. XX. PART II. , 4a 
