27 
with caustic soda lye. Another mode 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 quan- 
tities 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, in this respect resembling the colour of the petals 
of some flowers. I therefore had recourse to the plan 
adopted on a previous occasion, and described in a paper I 
had the honour of reading before this Society several years 
ago.^ A quantity of yarn made entirely of Nankin cotton 
(from the coast of Coromandel) was submitted to the 
usual process of bleaching, and the dark brown liquid ob- 
tained by treating the yarn with boihng alkaline lye was 
mixed with an excess of acid which produced a dark brown 
flocculent precipitate. This was filtered off, washed with 
water, and then treated exactly in the manner described in 
the paper just referred to. It was found to contain the 
same substances as the precipitate obtained in the same 
way from alkaline lyes with which ordinary Indian or 
American cotton had been treated, viz., cotton wax, fusing 
at the same temperature and having the same general pro- 
perties as that from ordinary cotton, a white crystalline 
fatty acid (probably margaric acid) pectic acid, parapec- 
tic acid, and lastly colouring matters. It is to the latter 
that the cotton owes its colour, for this colour is removed 
to a great extent by treatment with alkali, while the 
colouring matters are thrown down from the liquid 
* Memoirs, 3rd Series, toI. IY,, p. 95 
