Gold ornaments are polished using a liquid called aqua regia .
Aqua regia is a mixture of concentrated nitric acid and hydrochloric acid in the ratio of 1 : 3. It is a highly corrosive liquid.
It is a yellow-orange fuming liquid which can dissolve gold and platinum but not all metals.
When gold is dipped in aqua regia, the outer layer which had become lustreless, dissolves in aqua regia and the inner layer appears, thus making the gold look lustrous.
As the outer layer is dissolved in the aqua regia, hence some portion of gold is lost during this process. Therefore it has a slight loss in its weight.