38

DYEING AND CALICO PRINTING.

becomes hard and brittle again on cooling. It is insoluble in ether, and isaccordingly precipitated on the addition of ether to the alcoholic solution.When heated on platinum it melts, swells up considerably, and burns with abright, but smokeless flame, leaving a very voluminous coal, which graduallyburns away, only a slight trace of ash being left. It contains nitrogen, andwhen heated with soda-lime gives off ammonia in abundance. It dissolvesin concentrated sulphuric acid and in glacial acetic acid, giving dark brownsolutions, from which it is re-precipitated by water in brown flocks. It iseasily decomposed by boiling nitric acid, yielding a yellow solution, which onevaporation leaves an abundance of oxalic acid, but nQ picric acid. It iseasily soluble in caustic and carbonated alkalies, giving dark yellowish-brownsolutions, from which it is re-precipitated by acids in light brown flocks.The ammoniacal solution leaves, on evaporation, a dark brown amorphousresidue, which does not dissolve again entirely in water, in consequence of aloss of a part of its ammonia during evaporation. The ammoniacal solutiongives brown precipitates with the chlorides of barium and calcium, but nonewith sulphate of magnesia. With nitrate of silver it yields a dark reddish-brown precipitate, which dissolves completely in an excess of ammonia, givinga yellowish-brown solution, which remains unchanged on being boiled. Thealcoholic solution of the substance gives brown precipitates with the acetatesof baryta, lead, and copper. On the addition of an alcoholic solution ofpotash it gives a brown precipitate, which sinks rapidly, forming a glutinousdeposit. A similar effedt takes place when an alcoholic solution of soda isemployed. The substance is easily soluble in a boiling solution of acetate ofsoda, and is re-precipitated by acids in brown flocks. When the substancein a finely divided state, as obtained by precipitation from its alkaline solutionwith acid, is exposed for some time to the adtion of chlorine, its colour changesgradually from brown to pale yellow. After being filtered off and washedwith water, the produdt of the adtion dissolves easily in alcohol, and is left onevaporation as a brown transparent resin, which contains chlorine, but inother respedts closely resembles the original substance.

The analysis of this colouring matter led to results corresponding in 100parts to—

I. II. III. IV.

c .58-27 58-11 58-36 58-48

H . 6*42 6*40 5*9° 5*80

N . 8-03 — 522 5*31

O . 27*28 — 30*52 30*41

IOO'OO 100*00 IOO'OO

It will be seen that the composition of the substance varied, especially asregards the nitrogen, much more than it ought to have done, supposing it to havebeen perfedlly pure. In consequence of the amorphous nature of the produfi,it is difficult to determine whether Indian and American cotton contain twodistindl colouring matters, both easily soluble in alcohol and having the samegeneral physical properties, or whether in one or both cases the specimenssubmitted to analysis, though essentially the same substance, were notchemically pure. It is difficult to obtain, in a state of purity, an uncrystal-Usable resinous body having few charadleristic properties ; and the resultsarrived at by examining the composition of such bodies are seldom satisfactory.