Question

A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?​

Answer 1

• The goldsmith had used a solution of aqua regia, which is a mixture of conc. nitric acid and conc. hydrochloric acid in 1:3 ratio.
• Aqua regia has the ability to dissolve metals with low reactivity, like platinum and gold.
• The outer layer of gold dissolves as soon as it is dipped in aqua regia thus exposing the inner shiny layer of gold present beneath.
• As a result, the piece of jewellery loses weight and also gets a sparkling appearance.