noun
- Plural of copperas; a green or blue-green crystalline compound of iron sulfate, used historically in dyeing, ink production, and metal treatment.
Usage: chiefly historical or technical; also called ferrous sulfate or green vitriol
Examples
- Medieval dyers relied on copperases to fix certain colors in fabric.
- The old recipe called for copperases dissolved in water to create a dark ink.
- Copperases were mined and processed in large quantities during the Industrial Revolution.
- The chemist ordered several batches of copperases for the laboratory experiments.
- Historical documents mention the use of copperases in tanning leather.