A man went door to door posing as a goldsmith. He promised to bring back the glitter of the old and dull 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's actions and the outcome suggest that he used aqua regia to clean the gold bangles. Aqua regia is a mixture of one part by volume of concentrated nitric acid and three parts by volume of concentrated hydrochloric acid. It is known for its ability to dissolve noble metals like gold and platinum.
When the man dipped the bangles in aqua regia, outer layer of gold dissolved in it. So, although the bangles sparkled like new but their weight was reduced drastically.