This week I was lucky enough to be sent a silvered bottle, shown in the graphic, by Andres Tretiakov. If you’re a chemist you’ll already be familiar with the chemical reaction used to produce this effect, but if you’re not you might be wondering how it’s accomplished. Though sadly it’s not one that can be easily carried out at home, this graphic gives an insight into the chemistry involved!
Silver tarnishes in air to form a black coating of silver sulphide, which has the formula Ag2S. The chemical equation for the formation of silver tarnish following reaction with hydrogen sulphide (H2S) is as follows:
2 Ag(s) + H2S(g) → Ag2S(s) + H2(g)
There’s speculation that, in the present day, tarnishing of silver actually occurs more quickly due to the increased amounts of hydrogen sulphide being released into the atmosphere by the combustion of fossil fuels and the like. This silver sulphide tarnish can be quite easily removed using polishes that contain abrasives to rub off the silver sulphide, but these have the disadvantage of also removing small amounts of silver. Handily, chemistry provides a method which sidesteps this problem.
