CONSTITUENTS OF COTTON-FIBRE. 127 



concentrated sulphuric acid to act on it in the cold. The 

 substance first caked together, and then gradually dissolved, 

 forming a clear yellow solution, which, when mixed with 

 water, gave an abundant yellow flocculent precipitate. 

 This precipitate, after being filtered off and completely 

 washed, was found to consist of a substance which could 

 hardly be distinguished from the original colouring-matter. 

 After being dried, it appeared brown and resin-like ; and 

 on being heated, it burned away easily, but without the 

 least explosion or deflagration. It was insoluble in boiling 

 water, in which it merely melted to a resinous cake. It 

 dissolved easily in alcohol and alkalies, giving yellow solu- 

 tions, but was insoluble in ether. The alcoholic solution 

 left, on evaporation, a brown, brittle, resin-like residue, 

 just like the original substance. Colouring-matter B, 

 when treated in the same way, behaved similarly, and 

 yielded a product which could not be distinguished from 

 the colouring-matter itself, and was also decomposed with- 

 out any explosive action on being heated. It should be 

 mentioned, however, that in each case the product, when 

 heated in a sealed tube at ioo° C. for several hours, seemed 

 to undergo a slight decomposition, resulting in the for- 

 mation of a small quantity of acid, the nature of which 

 could not be determined ; but in other respects no marked 

 change of properties could be discovered. Parapectic acid, 

 when treated with the acid mixture, behaved very diff'erently. 

 It swelled up at first, and sank down in thick flocks, 

 which, after prolonged contact with the acid, remained un- 

 dissolved, and apparently unchanged; but on adding a 

 large quantity of water they dissolved completely, showing 

 that a conversion into metapectic acid had probably been 

 eff'ected. It is not probable, therefore, that these impurities 

 of the fibre, even when their amount is considerable, exert 

 any influence on the quality of the gun-cotton made from 

 it. The colouring-matters are dissolved by the acid, and 



