It07:Copper Hydrogen Arsorite

Scheele's Green

Taken from http://de.wikipedia.org/wiki/Carl_Wilhelm_Scheele

Developed in 1775, by the Swedish-German chemist Carl Wilhelm Scheele, Scheele's green (also known as Schloss green- Schloss meaning castle/mansion in German), CuHAsO3 is a cupric hydrogen arsenite with a yellowish green colour. It is the predecessor to the more vibrant Paris Green (also known as Schweinfurt Green, or Emerald Green) and was used as an insecticide, as well as a pigment, until the hazards connected to its use were acknowledged. Before the discovery of this compound, the known green pigments were based on copper carbonate and had the tendency to fade, which made this choice of colour unsustainable. The popularity of Scheele's green was based on its bright colour, as well as the fact that it was a lot more durable than previous pigments, which meant that the colour green could be used in its full splendour, without having to worry too much about its progressive degradation.

3-D image of the molecule

Pentahelicene

Preparation

The pigment was prepared by dissolving potash (an impure form of potassium carbonate) and arsenic sulphide in water. After heating this mixture, it was slowly added to a warm solution of copper sulphate and allowed to precipitate. The precipitate was then separated from the liquid and heated slightly to dry it.

Uses

The beautiful green colour of this compound meant that it was largely used in pigments- be these for paints, dyes for cloths, or otherwise. It was even used to colour foodstuffs, such as sweets and alcoholic beverages, to colour candles and to paint toys. Later, once its toxicity was vaguely understood, Scheele’s green was used as an insecticide.