34 Proceedings of the Royal Irish Acadenvj. 



This is the final result ; but at the same time there is fonned, in 

 considerable quantity, the so-called carlo-^vjrrol-araide, of which pyrrol 

 is usually regarded as a direct decomposition-product : — 



Ammouimn mucate. Carbo-pyrrol-ainide. 



CeHg {'S^iX Os = C.5H6^^20' + COo -f 5H2O. 



"We may then assume that, by the action of a molecule of nascent 

 water on carbo-pyrrol-amide, pyi'rol is formed. 



CsHels^oO + HoO = C.HsIy" + Is^Hs + CO,.. 



This view is borne out by the fact that if the amide be boiled with, 

 barium hydi'ate, ammonia is eTolved, and the barium salt of the mono- 

 basic carlo-i)])rrolic acid is obtained in solution (Schwanert) : 



Carbo-pyiTolic acid. 

 Q-^^.O + HoO = C4H,X"(C00H) + Is^Hs; 



which acid, at a temperature slightly above its fusing-point, splits up 

 into pyiTol and carbonic anhydiide, 



C.HiX (COOH) = G^-^ + CO3. 



This decomposition may be compared with, those by which phenol 

 is produced on heating salicylic and paraoxybenzoic acids ; citra- 

 conic and itaconic acids on heating aconitie acid, etc. Carbo-pyr- 

 rolic acid may then be regarded as a carboxyl derivative of pyiTol : 

 that is, as pyrrol in which the gi'oup COOH takes the place of an 

 atom of hydrogen. 



PjTrolis a coloiirless pleasantly-smelling liquid, boiling at 133° C. 

 It dissolves, although slowly, in dilute mineral acids ; but all attempts 

 to obtain simple or double salts of it have failed. The t'ee base, how- 

 ever, gives with an alcoholic solution of mercuric chloride a semi- 

 crystalKne precipitate, CiHgl!^, 2HgCl2, which, may be compared with. 

 the precipitates produced by ammonia under the same circumstances. 



Pyrrol is an extremely unstable compound. Exposed to air, it soon 

 becomes brown, and its solutions in acids decompose, slowly in the 

 cold, rapidly on boiling, into ammonia and the so-called pyrrol-red, 

 CjaHiiN'oO (Schwanert), CioHjoOo (Limpiicht). Other of its reactions 

 ■wiU be alluded to farther on. 



Eespecting its chemical constitution, Kckule ( " Lehrbuch der Che- 

 mie," vol. ii., p. 408) views it as an amine, one atom of hydrogen in am- 



C.Hsj 

 monia being displaced by the radicle CiHg, thus, H > N. Wichel- 



b: ) 



haus,^ however, has shown that this view is untenable, since it reacts 

 neither with chloroform, with bisulphide of carbon, nor with ethyl 

 iodide, with which reagents all primary amines combine energetically. 



2 " Berichte der deutschen Chemisclieii Gesellscliaft," ii. 



