Chemical Properties
Bright yellow monoclinic crystals. Density 6.12 g/cm??, melting point 844°C. Insoluble in water, oil, and acetic acid, but soluble in strong alkalis and inorganic acids. It turns black in contact with hydrogen sulfide and orange-red in contact with alkali. It has strong tinting and hiding power. It cannot be used with lithopone or ultramarine. It is toxic. Its color shade varies depending on the raw material ratio and preparation conditions, and includes five types: orange chrome yellow, dark chrome yellow, medium chrome yellow, light chrome yellow, and lemon yellow. Lemon chrome yellow [3PbCrO4·2PbSO4+Al(OH)3+AlPO4]. It contains at least 50% lead chromate and has a vibrant greenish hue. It produces a good gloss finish in paints. It can be mixed with blue pigments to produce a vibrant emerald green, equivalent to 10G. It has a lightfastness rating of 4-5. It has a heat resistance rating of 140°C. Its water and oil permeability are rated 1. Acid and alkali resistance is Class 3.
Light Chrome Yellow (5PbCrO4·2PSO4+Al(OH)3+AlPO4). Containing at least 60% lead chromate, it offers bright color, strong tinting strength, and excellent gloss in paints. It can be mixed with blue pigment to create a light green. The lead chromate content is higher than that of lemon chrome yellow. Its color is equivalent to 4G. Its lightfastness reaches Class 5. Its heat resistance is 140°C. Its water and oil permeability are Class 1. Its acid and alkali resistance are Class 3.
Medium Chrome Yellow (PbCrO4+PbSO4). It has a pure color and good gloss in paints. It can be mixed with blue pigments to produce a medium green. It has the highest lead chromate content, exceeding 90%. Its color is equivalent to Grade G. Its lightfastness reaches Grades 4-5. Its heat resistance is 140°C. Its water and oil permeability are Grade 1. Its acid and alkali resistance are Grade 3.
Dark Chrome Yellow (PbCrO4+PbCrO4·PbO). It contains 85% lead chromate, has a reddish hue, and strong tinting strength. Its color is equivalent to Grade GR. Its lightfastness reaches Grade 5. Its heat resistance is 140°C. Its water and oil permeability are Grade 3.
Orange Chrome Yellow (PbCrO4·PbO). This is a basic lead chromate with a PbCrO4 content of at least 55%, resulting in an orange-yellow color. It has good lightfastness, reaching Grades 5-5. Its heat resistance is 150°C. Its water and oil permeability are Grade 1. Its acid and alkali resistance are Grade 3.
Definition
ChEBI: Lead chromate is a chromium coordination entity comprising chromate and lead(2+) ions in a 1:1 ratio It has a role as a carcinogenic agent, a neurotoxin and a nephrotoxin. It is a lead coordination entity and a chromium coordination entity. It contains a lead(2+) and a chromate(2-).
