copperas
/ˈkɑpərəs/
noun
- A green crystalline substance (iron(II) sulfate) used in dyeing, making ink, and treating water.
- In the 19th century, copperas was commonly used to make black ink.
- Gardeners sometimes add copperas to the soil to correct iron deficiency.
- The old dye works stored barrels of copperas for fixing colors to fabric.
Synonyms