Pigments through the Ages - Technical Information

About the chemical structure:

Chemical name:	lead(II)-chromate
Formula:	PbCrO₄
Crystal system:	Monoclinic - Prismatic (at Mineralogy Database)
Refractive index:	alpha = 2.31, beta = 2.37, gamma = 2.66

Color:

Color Index (C.I.)

PY 34

How can you identify Chrome yellow?

Imaging:

OM: the pigments are microscopically identified by their crystalline particles, the deeper shades having a more rectangular shape. The lighter, more yellow shades have finer particles.

Analytics:

It's identified by means of FTIR and Raman. It is also identified chemically by a change to black in sodium sulfide. In nitric acid, the orange turn's bright yellow and the yellow is only slightly affected. In other acids, the yellow turns red.

Raman spectra: University College London;

FTIR spectra: IRUG;

Usage and handling:

Permanence:	Toxicity:
Lightfast: poor. Degradation processes: it tends to fade when exposed to sunlight. The darker shades were known to brown over time. All chrome colors were blackened by sulfur-bearing air and the yellow variety sometimes would turn green when mixed with organic pigments. Because the pigment tends to oxidize and darken on exposure to air over time, and it contains lead, a toxic, heavy metal, it has been replaced by cadmium yellow.Chrome pigments were fast drying in oil and more permanent in oil than in watercolor.	toxic. MSDS: PIGMENT SANAS

Permanence:

Toxicity:

Lightfast: poor.

Degradation processes: it tends to fade when exposed to sunlight. The darker shades were known to brown over time. All chrome colors were blackened by sulfur-bearing air and the yellow variety sometimes would turn green when mixed with organic pigments. Because the pigment tends to oxidize and darken on exposure to air over time, and it contains lead, a toxic, heavy metal, it has been replaced by cadmium yellow.Chrome pigments were fast drying in oil and more permanent in oil than in watercolor.

toxic.

MSDS: PIGMENT SANAS

Literature:

Burton, G. et al., Chemical Storylines (Salters Advanced Chemistry), Heinemann, Oxford 1994, s. 204

Ramette, R. W., Precipitation of lead chromate from homogeneous solution. A lecture demonstration or laboratory experiment, J. Chem. Educ., 49, 1972, s. 270.

Artists’ Pigments A Handbook of Their History and Characteristics, Vol. 1, L. Feller, Ed., Cambridge University Press, London 1986, p. 187 - 204