DESTRUCTIVE DISTILLATION OF ANIMAL MATTERS. 587 



was a mixture, it was shaken up with a small quantity of dilute acid, and the 

 watery solution withdrawn. On the addition of caustic potash to this solution, 

 an oil separated, which had the smell of picoline mixed with that of pyrrol. For 

 the purpose of separating this picoline, the whole of the larger fractions were 

 mixed and shaken up with a small quantity of very dilute sulphuric acid, and 

 the solution, after being siphoned off, was replaced by another quantity, and 

 this was repeated a third time. The oil was thus diminished by about a third 

 of its bulk, and the whole of the picoline or other bases appearing to have been 

 removed, it was carefully dried by means of sticks of caustic potash, and again 

 rectified, when its boiling point was found to have been materially reduced. It 

 began to boil at much the same temperature as the crude oil, but the largest 

 fraction was now collected between 270° and 280°, while that which boiled above 

 290° formed only a very small proportion of the whole ; and after fifteen rectifi- 

 cations, it was obtained in such a state that it distilled almost entirely between 

 274° and 280°. In this condition it is a transparent and colourless oil, slowly 

 acquiring a brown colour when exposed to air and light. It has a strong fetid 

 smell, quite distinct from that of picoline, and a hot pungent taste. A piece of 

 fir-wood, dipped in hydrochloric acid brought near its vapour, instantly acquires 

 a fine red colour. When boiled with a dilute acid, it is immediately converted 

 into a red resinous mass, which fills the fluid so completely, that the vessel con- 

 taining it may be inverted without anything escaping. The fluid filtered from 

 this substance is brown, and contains a small quantity of it in solution. After 

 boiling for some time, so as to get rid of a peculiar smell which adhered to the 

 fluid, and decompose the last traces of pyrrol, caustic potash was added, when 

 the smell of ammonia, faintly contaminated with that of picoline, was evolved. 

 The solution having been distilled, the ammonia was saturated with hydrochloric 

 acid and bichloride of platinum added, when the platinochloride of ammonium 

 was immediately precipitated, and the filtrate, on further evaporation, yielded 

 an additional quantity of that salt, along with some indications of a more soluble 

 platinum compound. For a long time I considered the oil prepared by the pro- 

 cess now detailed to be pyrrol in a state of as great purity as it was possible to 

 obtain it ; and, as will be afterwards seen, it gave in different preparations, 

 analytical results in perfect accordance with one another, and with its true 

 formula ; but in the course of examining the effect of different reagents upon it, 

 it was found that caustic potash exerted a very singular and perfectly unique 

 action, disclosed the presence of a small quantity of some impurity, and afforded 

 the means of removing it, when the properties of the pyrrol underwent a very 

 remarkable change. When pyrrol is mixed with five or six times its weight of 

 caustic potash in coarse powder, and heated over the lamp in a flask fitted with 

 a long tube, it at first cohobates very freely ; but if the temperature be gradually 

 raised, the fluid is found to distil up into the tube much less readily, and at 



VOL. XXI. PART IV. 7 T 



