PbCrO4

PbCrO4, also known as lead(IV) chromate, is an inorganic compound with the formula PbCrO4. It occurs naturally as the rare mineral crocoite, a bright red–orange crystal used by some Australian Aboriginal cultures as crushed pigment. The compound is synthesized by reacting lead(II) salts with chromic acid or by precipitating it from a solution containing lead and chromate ions. It possesses a monoclinic crystal structure and is insoluble in cold water, though it dissolves slightly in acidic solutions.

In the 19th and early 20th centuries, PbCrO4 was popularly used as a pigment, marketed under names such as chrome yellow, carmine red, or V.4 pigment. Its vibrant hue and lightfastness made it valuable for paints, inks, and dyeing. However, the compound is toxic due to its lead and chromate content; both constituents are hazardous, with chromate being a known carcinogen and lead being a neurotoxic heavy metal. Consequently, its use in pigments and other consumer products has largely been discontinued in favor of non‑toxic alternatives.

PbCrO4 is sometimes used in analytical chemistry as a reference material and in radiation shielding due to its high atomic number. Industrial handling of the compound requires proper protective equipment and adherence to regulations governing hazardous materials. Disposal must follow environmental guidelines to prevent lead or chromium contamination of soil and water.