# Verdigris

**Aerugo*; Greek *ios**

**Known today as.** Copper acetate, the green rust of copper.

Kind: Mineral  
Poisoning: Mercury, arsenic, lead, and antimony (https://thethinkingpress.org/materia-medica/poisons/heavy-metal)  
Toxic: yes

> **Caution.** Poisonous.

## What was it used for?

In salves to clean ulcers and eat away proud flesh, and in eye ointments.

## What does modern science say?

Poisonous; abandoned in medicine. Long used as a green pigment.

## Pharmacognosy and toxicology

- **copper(II) acetate**: basic and neutral
- **copper carbonate**: in the patina

**Mechanism.** A soluble copper salt: it precipitates proteins and kills bacteria and fungi on contact, which cleans an ulcer and eats proud flesh, and it is a powerful emetic by irritation of the stomach; absorbed, copper destroys red cells and the liver and kidney. It was the green of painters and the standard caustic of the surgeon’s shop.

**Dose.** A gram swallowed vomits and can kill; the external use in the old salves was at low strength.

**Standing.** Copper sulfate replaced it as the fungicide (Bordeaux mixture) and the emetic was abandoned; obsolete.

## What did the older authorities say?

**Dioscorides.** Describes its making by hanging copper over vinegar.

## Sources

- Dioscorides, *De materia medica* V.
- Goldfrank’s *Toxicologic Emergencies*, 11th ed. (2019), “Copper.”
- Scott, D. A. (2002). *Copper and Bronze in Art: Corrosion, Colorants, Conservation*. Getty.

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*Verdigris.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-09-25. The Thinking Press. https://thethinkingpress.org/materia-medica/verdigris

Historical description, not medical advice.