an alumlike substance derived from alunite.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use roche alum in a sentence
Or, wash the brass-work with a strong solution of roche alum, and polish it with tripoli.Mrs. Hale's Receipts for the Million | Sarah Josepha Hale
If one ounce of powdered roche-alum be put into a cask of four gallons of wine, it will make it fine and brisk in ten days.Mrs. Hale's Receipts for the Million | Sarah Josepha Hale
A strong lye of roche alum and water also improves the appearance of brass.