WHITES. Alum White.—Dry mix 2 lb. powdered alum, 1 lb. honey ; powder; calcine to white ness in a shallow dish, cool, wash, and dry, Chinese White.—Mix finely-ground zinc white into a cream with mucilage of gum tragacanth, grinding with a glass muller.
Permanent White.—Precipitate sulphate of barium from the chloride by adding dilute sulphuric acid.
Sp inlet White.—Tho softest and purest NN, hite chalk, elutriated. balled, and dried.
Sulphate of Lead.-1', ccipitate the pigment by adding dilute sulphuric acid to an acetic or nitric acid solution of litharge ; wash and dry. The clear liquid may be used indefinitely. Whiting.—Grnund chalk, balled and dried.
White-lead.—White-lead or carbonate of lead is made by placing metallic lead in contact with acetic acid in open earthenware vessels, and covered with tan, a number of these vessels forming a " stack," and the whole remaining thus for about 11 weeks, when the lead becomes completely carbonized. The stack is then pulled down, and the carbonate of had is ground and dried. Many
mixtures of white-lead and chalk are sold under fanciful and misleading names.
Wilkinson's 117nte.—Litharge is ground with sea-water till it ceases to whiten, and is then washed and dried.
Zinc White (Griffithe').—Chloride or sulphate of zinc is precipitated by means of a soluble sulphide—sodium', barium, and calcium sulphides have been used—and precautions are taktn that no iron present is precipitated. The precipitate is collected, dried, and calcined for some time at cherry-red heat, with careful stirring. It is raked out while hot into vats of cold water, then levigated and dried. It is an oxysulphide of zinc.