Lead Antimonate

A white precipitate of lead metantimonate is formed when a solution of antimonic acid is added to one of lead acetate. After drying in the air this precipitate has the composition Pb(SbO₃)₂.9H₂O, but when dried over sulphuric acid it loses 7H₂O leaving Pb(SbO₃)₂.2H₂O, which may really be PbHSbO₄.H₃SbO₄. The pigment known as Naples yellow is an antimonate of lead containing excess of lead oxide. It is prepared by heating just to fusion for two hours 1 part of tartar emetic, 2 parts of lead nitrate, and 4 parts of sodium chloride (Brunner), or by heating 1 part of potassium antimonate with 2 parts of red lead (Guimet). The product is washed with water, and a fine orange or yellow pigment results, which is employed in oil-painting and for staining glass and porcelain.