The oxymu"iatic acid has also been used from its bleaching power in the ma nufacture of paper ; either the linen rags from which the paper is to be made be ing blanched by it, or, what has been re garded as preferable, the pulp into which they are reduced being submitted to its action. This method, though once ex tensively practised in this country, has been relinquished by many of our paper manufacturers, as it has been found, that in paper prepared with it, in the course of a few years, the ink is altered, and its blackness even so much impaired, as to affbrd some reason for the suspicion that in time it will altogether fade ; nor is this confined to writing ink, but has been observed even in printing ink. The ef fect is no doubt to be ascribed to a slight impregnation of the oxymuriatic acid, and this indeed can often be rendered perceptible by its odour, by breathing on paper which has been bleached in this manner. It might no doubt be removed by very careful washing of the pulp; but we have been informed by some intelli gent paper manufacturers, that the addi tional labour which would be requisite for this would, upon the whole, render the method more expensive than the old one.
The process of bleaching by steam with an alkali at a high temperature might probably be advantageously employed. A branch of the manufacture, however, in which the acid necessarily must be used, is that of discharging the colours from coloured rags, or to remove the ink from waste written paper. Even printed paper has been whitened by its agency, combined with that of an alkali, to re move the oily matter, and made to afford at least a coarser kind of paper. Chaptal applied it to the purpose of restoring the colour of old books or prints, the paper being whitened by a very dilute acid, which did not act sensibly on the print ing ink.
Wax, reduced to thin plates, has been bleached by the oxymuriatic acid. The process succeeds best when the acid is used in the state of gas. Berthollet has announced a peculiar effect obtained from the action of oxymuriatic acid, that of giving the appearance of cotton to hemp or flax. The process consists in immers ing the flax, prepared by boiling, and by an alkaline solution in oxymuriatic acid of a certain strength, for some time, and alternating this immersion repeatedly with the action of an alkaline ley.