OF THE MORINDA CITRIFOLIA. 443 
sively on Turkey-red mordant, is of interest, as establishing the existence of a 
peculiar class of dyes hitherto totally unsuspected,—a class which may be exten- 
sive, and may yield important substances. It may serve also, in some respects, 
to clear up the rationale of the process of Turkey-red dyeing, which has long been 
a sort of opprobrium of chemistry. Although that process has been practised for a 
century in Europe, and has undergone a variety of improvements, no clear expla- 
nation of it was for a long time given, but it was supposed that, by the action of the 
dung, of which large quantities are employed, the cloth underwent a species of 
animalisation, as it was called, by which it acquired the property of receiving a 
finer and more brilliant colour than could be attached to it by purely mineral 
mordants. Recent experiments have, however, shewn that the oil, which is 
largely employed in the process, undergoes decomposition by long exposure to the 
air in contact with decomposing animal matter, and is converted into a sort of 
resinous matter, which constitutes the real mordant for Turkey-red. This has 
been pretty clearly made out by the experiments of WeIssceRBER.* He found 
that when cloth had been treated with oil, so as to give, when dyed, a fine rose- 
red colour, he could, by digestion with acetone, extract from it the altered oil; 
and as it was removed, the cloth gradually lost the power of attracting the colour- 
ing matter of madder, until, when it was entirely separated, the cloth passed 
through the dye without acquiring any colour. On the other hand, he found that, 
by applying the substance extracted by acetone in sufficient quantity to cloth, he 
could obtain the richest and deepest colours with madder, without the addition 
of any other substance whatsoever. These observations receive additional confir- 
mation from the experiments detailed in the present paper, as it must be suffi- 
ciently obvious that the dark red colour obtained on Turkey-red mordant with 
morindine, must be entirely irrespective of the alumina, on which that substance 
is incapable of fixing. 
I fully agree with the opinion expressed by PErsoz that the use of alum mor- 
dant, which is at present always employed in Turkey-red dyeing, will be entirely 
abandoned so soon as calico-printers have learned the method of modifying at 
will the oil which they employ, so as to bring it at once into the state in which it 
acts asa mordant. Some steps have been made in this direction, by making use 
of some chemical agents, as nitric acid and chloride of lime, for the purpose of 
acting on the oil; but the improvements which have been effected stop far short 
of what I believe will eventually be effected, when the system of pure empiricism 
which has been all along employed in this particular process of dyeing is aban- 
doned, and the subject submitted to really scientific investigation. It is understood 
that M. Cuevreut has entered upon the inquiry, and in his hands there is little 
doubt but that it will meet with a satisfactory solution. 
* Persoz, Sur l’Impression des Tissus, vol. i., p. 176. 
VOL. XVI. PART IV. 5U 
