MASSICOT, or Masticot, is a protoxide of lead, of a pale yellow colour, exceedingly varying in tint from the purest and most tender yellow or straw colour to pale ash colour or grey. It has in painting all the properties of the white lead, from which it is prepared by gentle calcination in an open furnace, but in tint with which, nevertheless, it soon loses its colour and returns to white: if, however, it be used pure or unmixed, it is a useful delicate colour, permanent in oil under the same conditions as white lead, but ought not to be employed in water, on account of its changing in colour even to blackness by the action of damp and impure air. It appears to have been prepared with great care, and successfully employed, by the old masters, and is an admirable dryer, being in its chemical nature nearly the same as litharge, which is also sometimes ground and employed in its stead.