Dr. Scliunck on Rubian and its Products of Decomposition. 505 



granular mass. When dried it coheres into hard lumps, which 

 are almost black, and are with difficulty reduced to powder. 

 When the dry substance is heated on platinum foil it emits a 

 sniell somewhat resembling that of burning peat and burning 

 horn, and then burns without much flame, leaving a considerable 

 quantity of residue, which, on being further heated, is soon con- 

 verted into a grayish-white ash, consisting almost entirely of 

 carbonate of lime. If erythrozym be well mixed while in a moist 

 state with water, a reddish-brown muddy liquid is formed, having 

 all the appearance of a solution. It is, however, no solution; 

 the erythrozym is merely suspended in the liquid, for on filtering 

 through paper a clear liquid passes through, while a mucilaginous 

 substance remains on the filter. The latter, on being mixed 

 with a solution of rubian, exerts the usual decomposing effect on 

 that substance, while the liquid, when tried in the same way, is 

 found to be entirely without effect. Hence it follows that ery- 

 throzym, after having once been precipitated from its watery 

 solution, even by alcohol, cannot again be dissolved in water. 

 The liquid obtained by treating erythrozym with water and fil- 

 tering, contains a small quantity of a substance, w^hich, from its 

 reactions, I conclude to be pectic acid, or some body nearly allied 

 to it. In fact, the method of preparing erythrozym implies that 

 all substances contained in the watery extract of madder, inso- 

 luble in alcohol, must be found mixed with it ; but since the 

 erythrozym itself by precipitation with alcohol becomes insoluble 

 in water, these substances may afterwards be easily removed by 

 treating with water. If the watery liquid in which the erythro- 

 zym is contained in a state of suspension be boiled, a sort of 

 coagulation takes place, and the erythrozym separates in the 

 shape of dirty red flocks, while the liquid retains a reddish colour. 

 The same effect is produced by adding alcohol or salts, such as 

 common salt or sal-ammoniac, the substance separating in dark 

 reddish-brown flocks, with a clear yellowish liquid floating above 

 them. That erythrozym is not an uncombined substance, but 

 a compound of an organic substance with lime, is proved by its 

 behaviour towards acids. If it be treated with any acid, even 

 acetic acid, its colour changes from reddish-brown to yellowish- 

 brown, and the filtered liquid is found to contain a considerable 

 quantity of lime. The yellowish-brown flocks left on the filter, 

 after all the excess of acid has been removed, do not again form 

 with water a mucilaginous liquid like the original substance; 

 and even an addition of lime water, though it restores the origi- 

 nal chocolate colour, does not reproduce that peculiar condition 

 of suspensibility in water characteristic of it in its original state. 

 The brown substance into which erythrozym is changed by the 

 action of acids is soluble in caustic alkalies, forming pale purple 

 Phil, Mag. S. 4. No. 35. Suppl Vol. 5. 2 L 



