BLEACHING. 175 



the sulphureous acid, either in the form of gas, or 

 combined with water, as directed for wool. 



Bleaching Prints and Printed Books. 



4 



An application has been made of the new mode 

 of bleaching to the whitening of books and prints 

 that have been soiled by smoke and time. 



Simple immersion in oxygenated muriatic acid, 

 letting the article remain in it a longer or shorter 

 space of time, according to the strength of the li- 

 quid will be sufficient to whiten an .engraving. 



If it be required to whiten the paper of a bound 

 book, as it is necessary that all the leaves should 

 be moistened by the acid, care must be taken to 

 open the book well, and to make the boards rest 

 upon the edge of the vessel in such a manner that 

 the paper alone be dipped in the liquid : the leaves 

 must be separated from each other, so that they 

 may be equally moistened on both sides. 



The liquor assumes a yellow tint, and the pa- 

 per becomes white in the same proportion j at the 

 end of two or three hours the book may be taken 

 from the acid liquor and plunged into pure water, 

 with the same care and precaution as recommended 

 in regard to the acid liquor, that the water may 

 exactly touch the two surfaces of each leaf. The 

 water must be renewed every hour, to extract the 

 acid remaining in the paper, and to dissipate the 

 disagreeable smell. 



By following this process, there is some danger 

 that the pages will not be all equally whitened, 

 either because the leaves have not been sufficiently 

 separated, or because the liquid has had more ac- 

 tion on the front margins than on those near the 



