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of a colour varying from light to dark brown, which are easily 
broken, showing a dull earthy fracture. Both colouring 
matters contain nitrogen, and they differ therefore in consti- 
tution from true resins, which they resemble in many of their 
properties. The peculiar colour of the so-called “Nankin 
cotton ” is probably due to a great excess of these colouring 
matters existing in the fibre. It is certainly not caused by 
oxide of iron. 
The purification of the pectic acid contained in the brown 
precipitate produced by sulphuric acid was not effected 
without difficulty. The best method, according to the 
author, consists in submitting it to a simple process of 
bleaching with chloride of lime, by which means the impurity, 
consisting of brown colouring matter, which adheres to it 
with great pertinacity, is destroyed. When pure it has the 
properties and composition ascribed to pectic acid by Fremy. 
The cotton itself probably contains pectose or pectine, which 
is converted into pectic acid by the action of the alkaline lye. 
About three-fifths of the brown precipitate consists of pectic 
acid. Of the remaining two-fifths the colouring matters 
constitute by far the largest part, the wax and fatty acid 
being present in very minute quantities. The albuminous 
matter was not isolated, but its presence was indicated by 
the formation of a small quantity of leucine, which took 
place when the brown precipitate was submitted to the 
action of hydrate of soda. A large quantity of oxalic acid 
was formed at the same time, no doubt from the pectic acid. 
In conclusion, the author makes some remarks in regard 
to the part which these bodies may be supposed to play 
during the process of manufacturing gun cotton. It has 
been asserted that the instability occasionally observed in 
gun cotton is to be attributed to the impurities in the raw 
fibre, forming, by the action of nitro-sulphuric acid, bodies 
which decompose spontaneously at the ordinary or a 
