A man went door to door posing as a goldsmith. He promised to bring back the glitter on 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?
The man had actually used the solution of aqua regia (mixture of cone. HCl and cone. HNO3 in the ratio of 3 :1 by volume) which has dissolved gold forming soluble auric chloride (AuCl3). 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, the original shine on the bangles got restored.