Which one of the following acid is used by goldsmith for cleaning of gold and silver articles ?
Sulphuric acid
Nitric acid
Hydrochloric acid
Phosphoric acid
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC NDA-2 – 2023
– Tarnish on silver is typically silver sulfide (Ag₂S), and tarnish on gold can involve sulfides or oxides depending on the alloy.
– Nitric acid (HNO₃) is effective in dissolving many metal oxides and sulfides, including silver sulfide tarnish, while not significantly affecting the noble metals like gold and pure silver (though alloys might react).
– Sulphuric acid (H₂SO₄) is a strong acid but not typically preferred for cleaning jewellery tarnish compared to nitric or hydrochloric acid.
– Phosphoric acid (H₃PO₄) is a weaker acid used in some cleaning agents (like rust removers) but not commonly by goldsmiths for gold and silver tarnish.
– A mixture of concentrated nitric acid and concentrated hydrochloric acid (in a 1:3 ratio), known as Aqua Regia, is capable of dissolving gold and platinum. This is used for refining or testing gold, NOT for cleaning finished jewellery.