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.

From Project Gutenberg

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

From Project Gutenberg

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.

From Project Gutenberg