To restore the colour of a 9-carat gold chain that has been burnt black and blue swill it in a warm solution consisting of 1 part of sulphuric acid to 20 parts of water; then rinse in clean warm water. If the colour appears too pale, swill again carefully in a warm solution consisting of 1 part of nitric acid to 10 parts of water; then r.nse in clean warm water, dry by rubbing in hot sawdust, and polish with rouge. If the chain is badly burnt, it may be necessary to electro-gild it.