Emerald Green

Synthetic inorganic pigment

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Composition and Properties of Emerald Green

Emerald green is copper (II)-acetoarsenite: 3 Cu(AsO₂)₂·Cu(CH₃COO)₂. It has been valued by the painters of the 19th century for its vivid tone and excellent stability. Later on, the production has been halted due to the extreme toxicity of the pigment.

Emerald green is soluble in acids and alkalis and can also be hydrolyzed by prolonged contact with water. The pigment is not very lightfast Emerald green darkens in contact with sulfur compounds such as cadmium sulfide (cadmium yellow).

Art Teachers' Materials

Richly illustrated presentation on the properties, preparation, identification and use of this pigment

Pigment

Painted swatch

Commercial product

Video: 'Emerald Green - The Deadly Pigment And Its Handling Characteristics' by Ryan Demaree

Names of Emerald Green

Alternative names

Paris green, Veronese green, Schweinfurt green, Mitis green, Vienna green, Imperial green

Color Index

PG 21, CI 77410

Word origin

From Old French esmeraude (12c.), from Medieval Latin esmaraldus, from Latin smaragdus, from Greek smaragdos “green gem” (emerald or malachite), from Semitic baraq “shine”.

From Online Etymology Dictionary

Schweinfurter Grün

German

Vert Véronèse

French

Verde di Schweinfurt

Italian

Verde de Schweinfurt

Spanish

Preparation of Emerald Green

Attention: Emerald green is highly toxic and should not be used by people not trained to handle it.

Emerald green can be prepared by a reaction of sodium arsenite and copper(II) acetate or alternately, by a reaction of sodium arsenite, copper II sulfate, and acetic acid.

Here is a recipe from the 19th century:

‘Dissolve in a small quantity of hot water, 6 parts of sulphate of copper; in another part, boil 6 parts of oxide of arsenic with 8 parts of potash, until it throws out no more carbonic acid; mix by degrees this hot solution with the first, agitating continually until the effervescence has entirely ceased; these then form a precipitate of a dirty greenish yellow, very abundant; add to it about 3 parts of acetic acid, or such a quantity that there may be a slight excess perceptible to the smell after the mixture; by degrees the precipitate diminishes the bulk, and in a few hours there deposes spontaneously at the bottom of the liquor entirely discolored, a powder of a contexture slightly crystalline, and of a very beautiful green; afterwards the floating liquor is separated.’

Image courtesy of Technisches Museum Wien

Video: 'Arsenic-based pigments' by Hegelrast

The mineral conichalcite has a similar chemical composition as emerald green, even though it has never been used as a pigment.

History of Use

Emerald green has been in use since its discovery in the first quarter of the nineteenth century. It was discontinued sometime in the second half of the twentieth century due to its toxicity. The following graph gives the frequency of its use in the paintings of the Schack Collection in the Bavarian State Art Collections in Munich (1).

An extensive collection of occurrences of this pigment in paintings from several historical periods can be found in the blog post ‘Pigment: Poison Greens‘ by The Eclectic Light Company.

References

(1) Kühn, H., Die Pigmente in den Gemälden der Schack-Galerie, in: Bayerische Staatsgemäldesammlungen (Ed.) Schack-Galerie (Gemäldekataloge Bd. II), München 1969.

Example of use

Paul Gauguin, Arlésiennes (Mistral), 1888

Vincent van Gogh, Madame Roulin Rocking the Cradle (La Berceuse), 1889, Art Institute of Chicago

Timeline for Green Pigments

Identification

Infrared Spectrum

IR-spectra at CAMEO Materials Database

Raman Spectrum

Spectrum by Ian M. Bell, Robin J.H. Clark and Peter J. Gibbs, Raman Spectroscopic Library
University College of London

X-Ray Fluorescence Spektrum (XRF)

XRF-Spectrum at CAMEO Materials Database

References

(1) Miliani, C. et al. (2004). Identification of nineteenth-century blue and green pigments by in situ x-ray fluorescence and micro-Raman spectroscopy. Journal of Raman Spectroscopy, 35, 2004, 610–615.

(2) Buti, D., Rosi, F., Brunetti, B. G., & Miliani, C. In-situ identification of copper-based green pigments on paintings and manuscripts by reflection FTIR. Analytical and Bioanalytical Chemistry, 405(8), 2013, 2699–711. doi:10.1007/s00216-013-6707-6

(3) F. Rosi, C. Miliani, I. Borgia, B. Brunetti and A. Sgamellotti J. Identiﬁcation of nineteenth-century blue and green pigments by in situ x-ray ﬂuorescence and micro-Raman spectroscopy. Raman Spectrosc. 2004; 35: 610–615.