Scheele's Green not the first to contain arsenic
I removed the claim that "Scheele's green was the first pigment to contain arsenic". Even though the reference claims that this is true, arsenic pigments such as Orpiment have been used since at least the middle ages. See for example pg 176 of "The Materials and Techniques of Medieval Painting" by Daniel V. Thompson and published by Dover in 1956.
Perhaps a different claim was meant, such as "Scheele's green was the first synthetic pigment to contain arsenic" or that "Scheele's green was the first green pigment to contain arsenic" but arsenic pigments for painting and glassmaking are well known from before the middle ages. Jeff Dahl 18:04, 2 September 2007 (UTC)