$A$ 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?

(A) The man must have used $Aqua$ $Regia$ to clean the ornaments.
$Aqua$ $Regia$ is a freshly prepared mixture of concentrated $HCl$ and concentrated $HNO_3$ in a $3:1$ ratio.
It is a highly corrosive and fuming liquid capable of dissolving noble metals like gold.
When the gold bangles were dipped in this solution,the outer layer of the gold was dissolved,exposing the fresh,shiny inner layer,which made the bangles look new.
However,because the outer layer of gold was dissolved into the solution,the total weight of the bangles was significantly reduced.