Monday, 6 October 2014

Thallium Artist's Paints & Crookes vs. Lamy

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Compounds of very toxic heavy metals - such as lead, cadmium, chromium, and arsenic - had been used as pigments in artist's paints for some time before Winsor & Newton announced their new thallium range in 1871. 

Caravaggio, Goya and Van Gogh all had suffered the effects of heavy metal poisoning - probably cadmium and lead. These new thallium pigments made the toxicity problems, of existing artist's paints, pale into insignificance. Here's some pigment compositions -

  • antimony white (antimony trioxide)
  • barium yellow (barium chromate)
  • cadmium red, orange or yellow (cadmium sulfide & selenide)
  • chrome green (prussian blue - iron(III) hexacyanoferrate(II), lead chromate)
  • chrome orange (lead carbonate)
  • chrome yellow (lead chromate)
  • cobalt violet (cobalt arsenate or cobalt phosphate)
  • cobalt yellow (potassium cobalt nitrate)
  • lead flake white (lead carbonate)
  • manganese violet (ammonium manganese(III) pyrophosphate)
  • molybdate orange (lead chromate, lead molybdate, lead sulfate)
  • naples yellow (lead antimonate)
  • paris green (copper(II) acetate triarsenite)
  • strontium yellow (strontium chromate)
  • vermilion (mercuric sulfide)
  • zinc yellow (zinc chromate)

  • Thallium is much, much more poisonous than the above compounds. In solution, thallium cations have similarities to those of potassium. So it is quickly assimilated into the human body via existing potassium uptake pathways, there to wreak havoc.

    Lemy, in 1861, did some horrific experiments with thallium, this from The pharmacology of Thallium and its use in rodent control By James Clyde Munch 1931 -

    Fortunately, Winsor & Newton had only shown these new pigments as a curiosity at the 1871 International Exhibition. It was only a decade since William Crookes discovered the element, and it was still very scarce. Here's Crookes' announcement of the discovery, followed by his discussion concerning the Frenchman Lemy's interest in thallium.

    And lastly, a couple of thallium experiments by Crookes, of a much more British nature than Lemy's -

    Chemical News, April 11, 1863

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    Unrelated to this post, below is an example of
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