purple of Cassius

[kash-uhs, kash-ee-uhs, kah-see-uhs]

noun

1. a purple pigment precipitated as a sol by the interaction of gold chloride and a solution of stannic acid and stannous chloride: used chiefly in the manufacture of ruby glass, ceramic glazes, and enamels.

Word History and Origins

Origin of purple of Cassius¹

1830–40; named after A. Cassius, 17th-century German physician

Example Sentences

Gold also, like silver, does not unite with oxygen readily, or remain in union with it at high temperature; therefore great care is required in the preparation of glass to be coloured by oxide of gold; the form in which it is used being generally that of the purple of Cassius, made by precipitating a salt of tin with a salt of gold.

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In solution minute quantities of gold may be detected by the formation of “purple of Cassius,” a bluish-purple precipitate thrown down by a mixture of ferric and stannous chlorides.

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When the gold is finely 193 divided, as in “purple of Cassius,” or when it is precipitated from solutions, the colour is ruby-red, while in very thin leaves it transmits a greenish light.

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At one time, indeed, a gold compound known as purple of Cassius was so employed, but this soon became obsolete on the introduction of madder purple.

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Purple of Cassius, or Cassius's Purple Precipitate, was discovered in 1683 by Cassius of Leyden.

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