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?

Explanation

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. The chemical reactions have been discussed in consult Section 3.5.