410 Rev., J. Barlow, on some Modifications [April 3, 



remain in close contact after the water has been withdrawn. This 

 was experimentally exhibited. It was also shown that, when the 

 vegetable fibres were long and strong (as those of the Daphne 

 papyraica, from which much of the Indian paper is made), the paper 

 possesses the requisite strength. In other cases the paper is 

 strengthened and rendered sufficiently impervious to fluids for all 

 requisite purposes, by being made to imbibe, during the process of 

 manufacture, vegetable or animal size. But all paper is liable 

 to be disintegrated by water, however strongly it may have been 

 sized. 



The chemical composition and properties of woody fibre were 

 then considered. The components of this substance are carbon, 

 hydrogen, and oxygen ; the last-named elements being combined in 

 the same proportion as they exist in water. In this respect, woody 

 fibre is identical with starch, dextrine, gum, and sugar. Unlike 

 these substances, it is insoluble whether in water, ether, alcohol, or 

 oil, and much more averse than they are to chemical change. Mr. 

 Barlow called attention to the enormous inconvenience which would 

 arise if water could dissolve cloth, or if vegetable tissues were 

 easily decomposed. It is, however, many years since Braconnot* 

 discovered that sawdust, linen, and cotton fabrics, &c. could be 

 made to part with a portion of their constituent hydrogen in 

 exchange for an oxide of nitrogen obtained from the decomposition 

 of the nitric acid with which they were treated. Pelouzef after- 

 wards applied this principle in operation on paper ; and to the same 

 principle must be ascribed the gun-cotton and collodion of Schon- 

 bein.J Taking what may be called the gun-paper (Pelouze's paper) 

 as a type of all these substances, Mr. Barlow showed by experiment 

 that it is inflammable and highly electrical, and that in consequence 

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

 five to three) of hyponitric acid (NO4) for an equal proportion of 

 hydrogen, it becomes 50 per cent, heavier than the paper out of 

 which it was converted. Gun-cotton is soluble in ether and potash : 

 the latter solution has the property of reducing silver, in a bright 

 metallic mirror, from the nitrate of that metal. 



The surface-action of vegetable fibre in receiving dyes was 

 then mentioned, in order to introduce some researches recently 

 made by M. Kuhlmann, Director of the Mint at Lille. § Led to the 

 investigation by the general notion that azotized substances, as 

 wool, silk, &c. are more susceptible of dyes than are vegetable 

 textures, M, Kuhlmann instituted a series m£ experiments on gun- 

 cotton, both woven and in the wool, by which he discovered that 



♦ Annales de Chimie, Vol. lii. p. 290. (1833.) 



t Comptes Rendus, tome xxiii. p. 809. (1846.) 



X Philosophical Magazine, Vol. xxxi. p. 7 (1847): and Athenseum for 

 1847, p. 100. 



§ Etudes sur la fixation des couleurs dans la Teinture ; Comptes Rendus, 

 tomexlii. p. 673. (1856.) 



