It is a substance that can kill people and poison water supplies, yet it's for sale on Craigslist, and there is no law that directly prohibits people from possessing or selling it.
Mercury exposure, particularly Mercury vapor exposure, can cause severe problems for humans from skin irritation, to muscle disorders, to death.
"With any exposure, it depends on the dose, but a high enough dose, it can kill you," Dr. Robert Emery of the University of Texas School of Public Health said.
Mercury is used, although less widely than in the past, for thermostats, thermometers, switches, and a variety of industrial products.
Recently, on Craigslist Houston, Local 2 Investigates was alerted to a curious ad for a mason jar filled with "12 pounds" of Mercury.
Local 2 Investigates made arrangements to meet the seller.
The seller, Rebecca Cleveland, a Southeast Texas resident said she had inherited the substance from her father who was both an electrician and experimenter.
"I mean you could poison the whole damn city with this," Cleveland acknowledged.
When Local 2 Investigates Joel Eisenbaum asked why she would sell something with that kind of potential for danger on Craigslist, Cleveland said, "I couldn't dispose of it properly, I couldn't give it away. I went through every avenue I had and Craigslist was the the last line."
Cleveland added she would not have sold the substance to kids or anybody who looked suspicious.
Local 2 agreed to help Cleveland find a safe place to dispose of the Mercury. It took several phone calls. No agency or disposal site in Cleveland's immediate area would take the Mercury. But the city of Houston's Solid Waste Department did gladly oblige our request to dispose and or recycle the substance.
"We had a good ending. Finally it went where it should and not in the trash," Cleveland said.