Silver becomes bluish

When silver turns blue

The American was actually pretty healthy. He only complained that he kept getting respiratory infections. On the other hand, he had been given various antibiotics over a long period of time - until he lost his job and therefore had to cancel his health insurance. Then, instead of the expensive antibiotics, he resorted to a supposedly equally good alternative: a drinking solution that contained colloidal silver, i.e. silver in an extremely fine distribution. Such liquids are often offered as panaceas, especially on the Internet, which are supposed to protect against all forms of infection.

It was precisely this remedy that caused the strange discoloration, the 61-year-old's doctors were able to prove: They took a tissue sample from the skin of his face and found black, metallic granules in the lowest layers. The diagnosis was clear: through the long, regular consumption of silver, the man had developed what is known as argyria, a disease in which the precious metal ingested is deposited under the skin.

This phenomenon, which is now quite rare, has been known for several hundred years. A team of US scientists was only recently able to find out what exactly happens chemically. In order to be able to trace the path of the silver particles, Robert Hurt from Brown University in Providence and his colleagues in the laboratory had - greatly simplified - recreated the three most important stations that the silver passes through on its journey: the digestive tract, the bloodstream and the skin.

Station one is the stomach with its low pH value and high concentration of hydrochloric acid. Under such conditions, the silver oxidizes to positively charged particles, so-called silver ions. This is a crucial step, explain Hurt and his colleagues, because: The metallic silver from which the particles are originally made can only pass through the digestive tract in extremely small quantities and pass into the blood. The ions, on the other hand, are treated by the body like any other salt and are even actively transported into the bloodstream.