COLOUR OF NANKIN COTTON. 367 



The colour of Nankin cloth having been successfully 

 imitated by depositing oxide of iron on and within the 

 cotton fibres in the manner well known to dyers, it might 

 be supposed that the colour of the cotton was due to iron 

 in some form. A few simple experiments, however, suffice 

 to prove that this is not the case. The cotton, on being 

 incinerated, leaves an ash which does not contain a larger 

 proportion of oxide of iron than that of ordinary cotton. 

 Moreover the colour is not removed by treating the cotton 

 with dilute mineral acids capable of dissolving oxide of 

 iron, while it disappears, though slowly, on treatment with 

 boiling alkaline lye. 



Another method of imitating the colour consists in 

 mordanting the fabric with alum and then dyeing with 

 oak bark, the process resembling that by which calico is 

 ordinarily dyed of a yellow or fawn colour. It is evident, 

 however, from its resisting the action of acids, that the 

 colour of Nankin cotton cannot be due to the presence of 

 a lake of alumina or any other base. 



In order to arrive at some conclusion regarding the 

 nature of the colouring-matter, it was necessary to employ 

 large quantities of material ; for though the colour looks 

 intense when the cotton is viewed in mass, it is in reality 

 produced by a small quantity of substance spread over a 

 large extent of surface. I therefore had recourse to the 

 plan adopted on a previous occasion, and described in a 

 paper read before the Society several years ago*. A quan- 

 tity of yarn made entirely of Nankin cotton from the 

 coast of Coromandel (generally called in Lancashire " Coco- 

 nado cotton," from the port of shipment) was treated with 

 boiling alkaline lye for several hours; and the resulting 

 dark brown liquid was drawn off and mixed with an excess 

 of acid, which produced a dark brown flocculent precipi- 

 tate. This was filtered off, washed with water, and then 



* Memoirs, 3rd Series, vol. iv. p. 95. 



