Purple of Cassius

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Description

A permanent red-violet pigment. Purple of Cassius was first made by Andreas Cassius in Germany in 1676. It is composed of fine particle Gold precipitated on hydrated stannic oxide when tin chlorides are mixed into a dilute Gold chloride solution. The addition of Potassium carbonate to the solution deepens the purple color. Purple of Cassius was used until the mid 19th century when it was replaced by Cobalt violet. The expensive pigment was used in miniature paintings and to make Ruby glass and ceramic glazes. When Tin is present as a red-violet painting pigment, there is also the possibility of Cochineal prepared on a tin substrate.

Synonyms and Related Terms

purple-of-Cassius; gold-tin purple; gold purple

Physical and Chemical Properties

  • Soluble in ammonia. Insoluble in water.
  • Resistant to high temperatures.

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