42 
MILDEW IN PAPER AND PARCHMENTS. 
undergoing the same change, in the same manner that yeast causes 
fermentation. Animal matter enters into combination with oxygen 
in precisely the same way with vegetable matter ; but as, in addi- 
tion to carbon and hydrogen, it contains nitrogen, the products of 
theeremacausisare more numerous — carbonate and nitrate of ammo- 
nia, carburetted and sulphuretted hydrogen and water ; and these 
ammoniacal salts greatly favour the growth of fungi. Now paper 
consists essentially of woody fibre, having animal matter as size 
on its surface. 
The first microscopic symptom of decay in paper is irregularity 
of surface, with slight change of colour, indicating the commence- 
ment of the processes just noticed ; during which, in addition to 
carbonic acid, certain organic acids are formed, as crenic andulmic 
acids, which, if the paper has been stained by a colouring matter, 
will form spots of red on the surface. Spots of the same kind are 
similarly formed on leather coloured during its manufacture. Pro- 
vided that fungi have not taken root-, the colour can be restored by 
ammonia or any alkali. The same process of decay goes on in 
parchment as in paper, only with more rapidity, from the presence 
of nitrogen in its composition. When this decay has begun to take 
place, fungi are produced, the most common species being Peni- 
cilium glaucum. They insinuate themselves between the fiber, 
causing a freer admission of air, and consequently hasten the 
decay. 
The substances most successfully used as preventives of decay 
are the salts of mercury, copper and zinc. Bichloride of mercury 
(corrosive sublimate) is the material employed in the kyanization 
of timber, the probable mode of action being its combination with 
the albumen of the wood, to form an insoluble compound insus- 
ceptible of spontaneous decomposition, and therefore incapable of 
exciting fermentation. The antiseptic power of corrosive sublimat 
may be easily tested by mixing a little of it with flour-paste, the 
decay of and appearance of fungi on which are quite prevented by 
it. Next to corrosive sublimate, in antiseptic value, stands the salts 
of copper and zinc. Chloride of zinc has been patented by Sir W. 
Burnett for the preservation of wood, sail-cloth, &c, and appears 
to succeed admirably. For use in the preservation of paper, the 
sulphate of zinc is better than the chloride, which is to a certain 
extent deliquescent. 
