white lead

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white lead, heavy, white substance, poisonous, insoluble in water, extensively used as a white pigment and base in paints. It is one of the oldest paint pigments used by humans. Chemically, it is basic lead carbonate, a mixture of lead carbonate and lead hydroxide. It is prepared in various ways. When used in paints, it is first ground into a fine powder and mixed with linseed oil. Its covering power is greater than that of most other white pigments, but its use has certain disadvantages. It reacts with hydrogen sulfide and some other sulfur compounds in the atmosphere, the lead combining with the sulfur to form lead sulfide, a dark substance. In paints made with white lead a chalky film is formed after some time. White lead is extremely poisonous, and painters who apply it are often afflicted with painter's colic (see lead poisoning) because of the absorption of too great a quantity into the body. White lead is used also in making putty and in the manufacture of certain pottery. Sublimed white lead is the basic sulfate of lead mixed with lead oxide and zinc oxide; it is also used as a white pigment. White lead is often adulterated with barite.