1857.] of Woody Fibre and their Applications. 411 



cotton or flax, thus azotized, will not take dye ; but that if either by 

 spontaneous, or else by artificially-produced decomposition, the fibre 

 loses part of its nitrous principles, it then actually combines with 

 colours much more energetically than it did»while in its natural 

 state. Specimens of the cloth, which M. Kuhlmann had experi- 

 mented upon, and which that gentleman had sent for illustration 

 of this subject, were exhibited. 



Having reminded the audience that, in all these cases, a change 

 in chemical constitution accompanied the change in physical pro- 

 perties, Mr. Barlow contrasted with the pyroxylised textures of 

 Kuhlmann and the ,gun paper of Pelouze, the woven fabrics sub- 

 jected to Mercer's process, and the Parchment-paper, the inven- 

 tion of Mr. Gaine. By acting on cloth with chloride of zinc, tin, 

 or calcium, with sulphuric and arsenic acid, and, especially, by the 

 caustic alkalis in the cold (the temperature sometimes being lowered 

 to — 10° Fahr.), Mr. Mercer has obtained many important effects 

 on the fineness and the general appearance of cloth, and its suscepti- 

 bility of dye. This subject was brought before the Royal Institu- 

 tion by Dr. Lyon Playfair, C.B.,* and it has since been closely 

 investigated by Dr. Gladstone.! Mr. Mercer also experimented 

 on the effect of acids on paper. It being known that sulphuric acid, 

 under certain conditions, modified vegetable fibre, Mr. Gaine insti- 

 tuted a course of experiments to ascertain the exact strength of 

 acid which would produce that effect on paper which he sought, as 

 well as the time during which the paper should be subjected to its 

 action. He succeeded in discovering, that when paper is exposed 

 to a mixture of two parts of concentrated sulphuric acid (s. g. 1 • 854, 

 or thereabouts) with one part of water, for no longer time than is 

 taken up in drawing it through the acid, it is immediately converted 

 into a strong, tough, skin-like material. All traces of the sulphuric 

 acid must be instantly removed by careful washing in water. If 

 the strength of the acid much exceeds or falls short of these limits, 

 the paper is either charred, or else converted into dextrine. The 

 same conversion into dextrine also ensues, if the paper be allowed 

 to remain for many minutes in the sulphuric acid after the change 

 in its texture has been effected. 



In a little more then than a second of time, a piece of porous and 

 feeble unsized paper is thus converted into the Parchment-paper, 

 a substance so strong, that a ring seven-eighths of an inch in width, 

 and weighing no more than 23 grains, sustained 92 lbs. ; a strip of 

 parchment of the same dimensions supporting about 56 lbs. Though, 

 like animal parchment, it absorbs water, water does not percolate 

 through it. Though paper contracts in dimensions by this process 

 of conversion into Parchment-paper, it receives no appreciable 

 increase of weight, thus demonstrating that no sulphuric acid is 



♦ Proceedings of the Royal Institution, Vol. i. p. 134. (1852.) 

 t Journal of the Chemical Society, Vol. v. p. 17. (1853.) 



