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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]