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 man had actually used the solution of aqua regia (mixture of conc. HCl and conc. `HNO_(3)` in the ratio of 3 : 1 by volume) which has dissolved gold forming soluble auric chloride `(AuCl_(3))`. Since gold actually reacted, there was a loss in weight of the gold bangles. With the removal of the dull layer of gold from the surface, there was original shine on the bangles.