7 ноября, 2015 
Pokraskin The chrome yellow pigments [1344-37-2], C. I. Pigment Yellow 34:77600 and 77603, are pure lead chromate or mixed-phase pigments with the general formula Pb(Cr, S)O4
[3.115] (refractive index 2.3-2.65, density ca. 6 g cm-3).
Chrome yellow is insoluble in water. Solubility in acids and alkalis and discoloration by hydrogen sulfide and sulfur dioxide can be reduced to a minimum by precipitating inert metal oxides on the pigment particles.
Both lead chromate and lead sulfochromate (the latter is a mixed-phase pigment) can be orthorhombic or monoclinic; the monoclinic structure is the more stable
[3.116] . The greenish-yellow orthorhombic modification oflead chromate is metastable
at room temperature, and is readily transformed to the monoclinic modification under certain conditions (e. g., concentration, pH, temperature). The latter modification occurs naturally as crocoite.
Partial replacement of chromate by sulfate in the mixed-phase crystals causes a gradual reduction of tinting strength and hiding power, but allows production of the important chrome yellows with a greenish yellow hue.
3.4.1.1
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