248 VI. METALS.— Sub-salts. 



ScHWEiNFURT GREEN, Vienna green, Vert de mitis. Dissolve 

 verdigris lib. in vinegar, and pour into it a solution of lib. white 

 arsenic in water ; add more vinegar to dissolve the sediment ; 

 evaporate and crystallize. The crystals are a fine bluish green. 



2. Boil lOlb. of the crystals with a solution of lib. of potash; 

 this will take off the blue tinge. 



jEs ustum. Copper, rough brimstone, ana p. seq. laid in 

 strata, common salt, a small quantity sprinkled on each layer, 

 exposed to the fire till the brimstone is burned out: when one 

 piece is rubbed against another, it ought to have a red colour like 

 cinnabar; caustic. 



LEAD. 



Flake white, Fine ivhite. Carbonate of lead, Cerussa vera, 

 Plumhi carhonas, P. suhcarhonas, P, oxidmn album. Made by 

 suspending rolls of thin sheet-lead over malt vinegar, or pyro- 

 ligneous acid, in close vessels, the evaporation from the acid being 

 kept up by the vessels being placed in a heap of dung, or a steam 

 bath. 



Nottingham white. Made with alegar ; does not discolour 

 so soon as the common. 



Newcastle white. Made with molasses vinegar. 



Grace's white lead. Made with the refuse water of the 

 starch-makers, the phlegm obtained in distilling rough turpentine, 

 brewers' grains, and exhausted hops, and any other similar matters. 



French white lead, Blanc de plomb. Dissolve litharge in 

 dilute acetic acid, and pass carbonic acid gas through the solution. 

 Fine white lead is astringent, cooling; used externally, or em- 

 ployed as paint, mixed with nut or old poppy oil ; it should be 

 completely soluble in nitric acid, and the solution should not yield 

 a precipitate when added to a solution of sulphate of soda ; con- 

 tains 14 protox. lead, with 2*75 carb. acid; equiv. 16*75. 



Wilkinson's white. Grind litharge with sea water, until 

 its whiteness does not improve. 



Mineral white. Dissolve lead or litharge in nitric acid, 

 add a solution of subcarb. of potash, as long as any sediment falls ; 

 wash and dry. 



White precipitate of lead, Sulphate of lead. Litharge 

 lib., strong nitric acid 4oz., water 8oz. ; after some time decant, 

 add oil of vitriol as long as a sediment falls : pour off the liquor 

 back on the litharge. A fresh solution will take place, and this 

 may be continued until the whole of the litharge is changed into 

 the white precipitate. Used as a white colour in miniature painting, 

 being both beautiful and durable. 



