VI. IMETALS.— Sub-salts. 249 



Patext yellow, Muriate of lead, Chloride of lead. Common 

 salt 1 cwt., litharge 4 cwt., ground together with water, kept for 

 some time in a gentle heat, water being added to supply the loss 

 by evaporation, the subcarb. of soda then washed out with more 

 water, and the white residuum heated till it acquires a fine yellow 

 colour : used as a paint. 



Naples yellow. Lead lib. and a half, common antimony 

 lib., alum and common salt of ea. loz. : calcined together. 



2. Flake white 12oz., diaphoretic antimony 2oz., calcined 

 alum half an oz., sal ammoniac loz., calcine in a covered crucible, 

 with a moderate heat, for three hours, so that at the end of that it 

 may be barely red-hot : with a larger proportion of diaphoretic 

 antimony and sal ammoniac, it verges to a gold colour. Used as 

 a yellow colour. 



lEON. 



PbussiAN blue, Cyanuret of iron^ Hydrocyanate of iron^ CcEru^ 

 hum Berolijieiise, Argol and saltpetre, 21b. of eacn, throw by 

 degrees into a red-hot crucible. Dry bullock's blood over the 

 fire, in an iron pan, mix 21b. of this dry blood with the prepared 

 salt, calcine it in a crucible till it no longer emits a flame ; then 

 dissolve common alum 41b. in water 26 pints, and strain the solu- 

 tion ; dissolve also dried green vitriol lib. in water 4 pints, and 

 strain while hot ; mix the two solutions together while boiling-hot ; 

 dissolve the alkaline salt calcined with blood in 30 pints water, 

 and filter through paper supported upon linen ; mix this with the 

 other solution, and strain through linen : put the sediment left 

 upon the linen, while moist, into an earthen pan, and add spirit of 

 salt lib. and a half, stir the mass, and when the effervescence is 

 over, dilute with plenty of water, and strain again ; lastly, dry the 

 sediment. Used for preparing the cyanuret of mercury. 



2. Mix lib. of Dantzic potash with 2lb. each of dried blood 

 and horns, put it into an iron pot, and keep it in a red heat till 

 it no longer flames or smokes; take out the pasty mass, when cold 

 (h\s/)lvc it in water, filter, eva[>oratc, crystallize, and rcdissolve the 

 crv^tc'ils in a pint and half of water. Then take green vitriol lib., 

 common alum lib. to 411)., mix and dissolve them in a gcxxl quan- 

 tity of water, by boiling, and filter while hot ; precipitate this 

 solution by the solution of prepared alkali, and filter. The pre- 

 cipitate will \ie the darker the less alum is added ; but at the same 

 time it will be greener from the great admixture of the oxide of 

 iron which is precipitated, and which must be got rid of by add- 

 ing, while it IS moist, spirit of salt, diluting the mixture with 

 water, and straining. 



3. Precipitate a solution of green vitriol with the solution of 

 prepared alkali, and purify the precipitate with spirit of salt ; pre- 



