APPENDIX. . (79) 



the clippings of plated copper, the ufe of which is very exten- ^X'eWc. 

 five. 



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

 fubftitution of it for four milk, v^as firft pubHlhed by Dr 

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

 buck's chemical friends, that he had tried it, found 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 ihortened. Much of it too is 

 ufed in preparing the befl 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 flrength and purity. The 

 dyers alfo employ great quantities of it in different proceffes, 

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

 ing with that drug. 



At firft, the manufacftories 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 w^ould 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 fhow, 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 

 fhould ftand on record, to whom chemifts and artifts are fo 

 much indebted for their fubfequent fuccefsful labours. 



The. 



