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. What is the solution in which he dipped the gold?

The solution is aqua regia. 
Conc. Hydrochloric acid and conc. Nitric acid is mixed in the ratio of 3:1. This freshly prepared mixture, which is known as aqua regia, is used as the solution by him. 

Aqua regia is capable of dissolving gold. Due to this dissolving capability, when the goldsmith dips the bangles in the aqua regia, some of the gold amounts are dissolved and hence the weight of the bangles is reduced.