roche alum

[rohch]

noun

Chemistry.

1. an alumlike substance derived from alunite.

Word History and Origins

Origin of roche alum¹

1400–50; roche cliff, rocky height (now obsolete), late Middle English ( rock ¹ ); apparently partial translation of Middle French alum en roque, alun de roche

Example Sentences

To dye white gloves of a beautiful purple, boil four ounces of logwood, and two ounces of roche alum, in three pints of soft water, till half wasted.

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By infusing brazil wood, French berries, or indigo in the vinegar, with a little roche alum, either red, yellow, or blue may be produced.

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This article must first be prepared, by being steeped for several days in a mixture of roche alum, vitriol, verdigris, and copper filings, infused in white wine vinegar.

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