OF THE MORINDA CITRIFOLIA. 443 



sively on Tui-key-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 

 centiu-y in Europe, and has undergone a variety of improvements, no cleai* 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 brUliant 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 pi'ocess, 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 Weissgeeber.* He found 

 that when cloth had been treated with oil, so as to give, when dyed, a fine rose- 

 red colour, tie could, by digestion with acetone, extract from it the altered oU ; 

 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 Tiu-key-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 Pebsoz 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 oU which they employ, so as to bring it at once into the state in which it 

 acts as a 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. Chevhecjl has entered upon the inquu-y, and in his hands there is little 

 doubt but that it will meet with a satisfactory solution. 



* Persoz, Sur I'Impression des Tissus, vol. iii., p. 176. 

 VOL. XVI. PART IV. 5 U 



