186 ON THE DEFECTS, ETC., OF CERTAIN PAPERS. 



However, we repeat, repressive measures must be adopted against 

 such a system of manufacture, at least as far as regards papers for 

 public documents, which necessarily require a guarantee of durability, 

 to be se cured only by sound paper made of white rags, of hemp, or of 

 flax, tub-sized. After verifying the good quality of the paper by its 

 rattle, rigidity, clearness, and resistance to breakage, the length of the 

 fibre on the torn edge of a sheet must be examined with a glass, and in 

 respect to writing papers, the equality of the sizing should be ascertained 

 by wetting. 



As was long ago proved by Baron Liebig, all vegetable substances 

 undergo, when placed in contact with moist air, a true slow combustion 

 or eremacausis. The oxygen of the atmosphere, combining in these 

 circumstances with the carbon that forms the essential constituent 

 element of the vegetable matter, there is formed one volume of carbonic 

 acid gas equal to that of the absorbed oxygen ; at the same time a por- 

 tion of the latter takes up a part of the hydrogen of the cellulose, to 

 form water. The porous state of the substance, which increases its 

 faulty absorption, favours this decomposition in a high degree. 



Substances of animal origin undergo an analogous decomposition ; 

 but here the presence of nitrogen contained therein, gives rise also to 

 the formation of ammoniacal salts, which specially favour microscopic 

 vegetable development of the cryptogamous class. Hence that formation 

 of mouldiness which is ordinarily observed under similar circum- 

 stances. 



Paper being formed, as we have seen, essentially of vegetable fibres 

 and of the gelatinous substances introduced in the sizing, is subject, 

 like every other organic substance, to decomposition or eremacausis, 

 more or less rapid, according to certain conditions of manufacture. But 

 it is easy to conceive that the presence of earthy matters in the paper 

 pulp, combined with the accelerated desiccation which the paper 

 undergoes, by diminishing its cohesion, can but increase the rapidity of 

 its decomposition. 



The first symptom of decay in the paper is generally manifested 

 by inequalities on the surface, which, in some places, become 

 fluffy, at the same time its whiteness is impaired. During this internal 

 decomposition, besides the carbonic acid above mentioned, traces of 

 organic acids, such as humic and crenic, form on its surface reddish 

 spots or holes, when the paper has been blued. In other cases, these 

 spots are yellowish or ochrish ; they sometimes arise from the scum, 

 caused by the imperfect mixture of the size with the pulp. When these 

 alterations are more advanced, a mouldiness is developed in these parts, 

 especially if the paper has been sized with gelatine, of which the most 

 common is a species of penicillium. These microscopic vegetations, 

 insinuating themselves between the pores of the paper, lessen its co- 

 hesion and accelerate its disintegration. 



According to M. Bjckramin, a printer in Treptow, these mouldy 



