Copper sulfate is a fascinating substance that burns with a green to aquamarine colored flame. Often it’s used in high school chemistry classes to demonstrate just such a phenomenon. It’s also considered a “green chemical” in that the US agricultural industry has used copper sulfate in pesticides since 1956. It is approved for use even in organic farming.

The copper in copper sulfate binds to proteins in bacteria, fungi and algae. It damages their cells, causing the organism’s cells to leak and die. Copper sulfate especially inhibits the growth of Esherichia coli. E. coli is an aggressive bacterium that is often the source of contamination in commercially grown produce.

Agricultural products containing copper sulfate are available in liquids, dusts and crystals. Copper sulfate can be toxic—and even lethal—if large amounts are absorbed through the skin. Accidental poisoning with this chemical has been reported occasionally among farm workers.

Workers can be exposed to the chemical as it comes into contact with skin. The dust can be breathed in, or the accidental contamination of food or drink can occur. That’s an interesting idea for the genesis of a murder mystery or thriller plot!

The chemical appears as a pale green powder, but when mixed in water it turns the liquid a bright blue—a telltale sign of the presence of copper sulfate.

Although copper is an essential element and required by the body for proper health, the human body has internal mechanisms to maintain proper copper equilibrium. Excess copper is not stored in the body but excreted in solid wastes. The body cannot handle sudden large doses of the chemical, however. It overwhelms the body’s defense mechanisms, resulting in tissue damage or even death.

As with most toxic chemicals, the degree of harm is proportionate to the dose. Smaller doses of copper sulfate cause nausea and vomiting, loss of appetite, shock and diarrhea. Larger doses can lead to tissue damage, destruction of blood cells and moderate to severe damage to the liver and kidneys. Lethal doses result in multi-organ failure resulting from the chemical binding to proteins in different organs.

An ingested dose of 15-20mg of copper sulfate causes mainly gastrointestinal symptoms, but higher doses can be lethal. Acute liver failure is the primary result of severe poisoning.

Accidental poisonings occasionally happen in the agricultural industry, but fortunately they have been on the decline with better education regarding safe handling of the chemical. Copper sulfate ingestion is also rare, and mainly is limited to the Indian subcontinent. This chemical is easily found in Sri Lanka and sold over the counter in that area of the world. Burning of copper sulfate in houses and shops as good luck charms or for religious activities has been a common practice among local Buddhists and Hindus.

The colorful flames from burning the hydrated crystals are attractive to children and a source of inadvertent ingestion and poisoning. The chemical is also commonly used there in pesticides, in the leather-making industry and for making homemade glue.

For an interesting poison in your next murder mystery, copper sulfate might be the perfect chemical weapon. It’s easy to use, readily available on the Internet and particularly lethal in sufficient quantities.

Thoughts? Comments? I’d love to hear them!