Zinc yellow
Composition and Properties of Zinc Yellow
Zinc yellow is a complex zinc potassium chromate with a formula of K2O · 4 ZnCrO4 · 3 H2O.The pigment is soluble in acids and in alkalis (1), but it is not very lightfast and can change its colour to gray-green due to the reduction of the chromate ion to chromium 3+ ion (1). Newer research shows that it can also change its colour to dirty brown due to the reaction of the chromate ion to dichromate ion (2 and 3). The exact mechanism of this degradation is described in the tab ‘Discoloration’ on the page about Seurat’s painting ‘A Sunday Afternoon on the Island of La Grande Jatte‘.Zinc yellow is compatible with all non-alkaline pigments.
Names
Ultramarine yellow, yellow button of goldPY 36, CI 77955Zinc: from German Zink, perhaps related to Zinke “prong, point;” said to have been used first by Paracelsus (c. 1526) on analogy of the form of its crystals after smelting. Zinke is from Old High German zint “a point, jag,” from Proto-Germanic *teng– “tine”From Online Etymology Dictionary
Preparation of Zinc Yellow
Attention: All chromates and dichromates are highly toxic chemicals and should not be used by people not trained to handle them.The pigment can be precipitated from the mixture of solutions of a chromate salt, potassium salt and a zinc salt. The precipitate can then be filtered, dried and homogenized in a mortar.
History of Use
It was first synthesized at the beginning of the nineteenth century but was not used as a pigment until the 1850s.Examples of use
