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Table 1 Chrome, barium, zinc and strontium yellow pigments: common and chemical names, chemical formula, colour index number (C.I.), refractive index, solubility product constants (K sp at 25 °C), crystal structure and space group [8,9,10,11]

From: Barium, zinc and strontium yellows in late 19th–early 20th century oil paintings

Common names Chrome yellow Barium yellow
Lemon yellowa
Zinc yellow
Citron yellow
Strontium yellow
Strontian yellow
Chemical name Lead chromate Barium chromate Zinc potassium chromate hydrate Strontium chromate
Chemical formula PbCrO4 BaCrO4 4ZnCrO4·K2O·3H2O SrCrO4
C.I. pigment yellow 34:77600 31:77103 36:77955 32:77839
Refractive index 2.3–2.65 1.94–1.98 1.84–1.9 1.92–2.01
K sp 1.8 × 10−14 1.17 × 10−10 3.3 × 10−11b 3.5 × 10−5
Crystal structure Monoclinic Orthorhombic Monoclinic Monoclinic
Space group P21/n Pnma P21/n P21/n
  1. aThe designation “lemon yellow” was also used for zinc and strontium chromates [5] but herein it will only refer to barium chromate
  2. bThe solubility product constant of zinc yellow is not tabulated. It was calculated using the data from Simonsen et al. [12]