大象传媒

The presenter talks to a doctor about the use of metals in the human body. They look at the X-rays of a swimmer with metal implants in her legs. The presenter wants to know why gold, the least reactive metal, is not used for implants. The doctor explains it is used for teeth but is too soft for holding bones together - for this task titanium is used. Titanium is more reactive than gold but forms a protective, harmless and stable oxide layer when exposed to oxygen.