APPENDIX. , (79) 



the clippings of plated copper, the ufe of which is very extea- ^J-^L 



five. 



The application of the vitriohc acid in bleaching linen, or a 

 fubftitution of it for four milk, was firft publifhed by Dr 

 Francis Home. But it is well known to feveral of Dr Roe- 

 buck's chemical friends, that he had tried it, foiind it effedlual, 

 and had frequently recommended it to bleachers before the 

 date of that publication. The quantity of it now confumed 

 in that art is very great. Of late it has been ufed in decompo- 

 fing common fait, with the addition of manganefe, in order to 

 obtain the oxygenated muriatic acid, by which the procefs of 

 bleaching fine linen is amazingly fhortened. Much of it too is 

 ufed in preparing the beft kind of aquafortis, or nitrous acid, 

 from faltpetre, which was decompofed formerly, and ftill is, in 

 many cafes, by vitriol, Inftead of the vitriolic acid ; but the vi- 

 triol gives an aquafortis of inferior ftrength and purity. The 

 dyers alfo employ great quantities of it in different proceffes, 

 particularly in dlffolving indigo, in one of their methods of dy- 

 ing with that drug. 



At firll, the manufa<ftories of the vitriolic acid in Britain 

 fupplied foreign nations as well as our own, though foreigners, 

 having fince difcovered or learned the art, now make it them- 

 felves. But it would be tedious to mention all the applications 

 of it which have been already made, and it is impofllble to fay 

 how far the ufe of this powerful agent in chemiftry, and the 

 arts, may be carried. Enough has been faid to Ihow, that Dr 

 Roebuck's difcoveries, in that department, have been of the 

 greateft advantage to fcience and the pracflical arts, in facilita- 

 ting the procefs for procuring this acid, and in rendering it of - 

 general ufe ; and it is but fair that the name of that perfon 

 fliould ftand on record, to whom chemifts and artifls are fo 

 much indebted for their fubfequent fuccefsful labours. 



Tre, 



