question_answer

  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?

Answer:

                  Goldsmith dipped the set of the gold bangles in aqua regia solution. Aqua regia is a freshly prepared mixture of 1 part of cone. HNO3 and 3 parts of cone. HCl by volume. Aqua regia dissolved a considerable amount of gold from the dipped gold bangles and hence reduced their weight drastically. The goldsmith (dishonest) can recover the dissolved gold from aqua regia by a suitable treatment.