CHEMICAL SCIENCE. 325 







sequence of the substitution of a certain number of equivalents (varying 

 from live to three) of hyponitric aicd (NO-i) for an equal proportion of 

 hydrogen, it becomes fifty per cent, heavier than the paper out of which 

 it was converted. 



The surface-action of vegetable fibre in receiving dyes was then men- 

 tioned, in order to introduce some researches recently made by M. Kuhl- 

 mann, Director of the Mint at Lille. Led to the investigation bv the 



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general notion that azotized substances, as wool, silk, &c., are more sus- 

 ceptible of dyes then are vegetable textures, M. Kuhlmann instituted a 

 series of experiments on gun-cotton, both woven and in the wool, by 

 which he discovered that cotton or flax, thus azotized, will not take dye ; 

 but that if either by spontaneous, or else by artificially-produced decom- 

 position, the fibre loses part of its nitrous principles, it then actually com- 

 bines with colors much more energetically than it did while in its natural 

 state. Specimens of the cloth which M. Kuhlmann had experimented 

 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 

 properties, Mr. BarloAV contrasted with the pyroxylized textures of Kuhl- 

 mann and the gun-paper of Pelouze, the woven fabrics subjected to Mer- 

 cer's process, and the Parchment-paper, the invention 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 tem- 

 perature sometimes being lowered to 10 Fahr.), Mr. Mercer has ob- 

 tained many important effects on the fineness and the general appearance 

 of cloth, and its susceptibility of dye. It being known that sulphuric acid, 

 under certain conditions, modified vegetable fibre, Mr. Gaine instituted 

 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 dur- 

 ing 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. l - 854, or thereabouts) with one part of 

 water, for no longer time than is taken up in drawing in 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 wash- 

 ing 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 dex- 

 trine. 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 twenty-three grains, sus- 

 tained ninety-two pounds ; a strip of parchment of the same dimensions 

 supporting about fifty-six pounds. Though, like animal parchment, it 

 absorbs water, water does not percolate through it. Though paper con- 

 tracts in dimensions by this process of conversion into Parchment-paper, 



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