The coal gas used for lighting will sometimes cause silver and plated goods kept near the gas burners to become discoloured. This blackening is caused by the presence of sulphuretted hydrogen in the gas. No special form of burner will prevent the blackening of the silver if the gas is impure, though the use of an incandescent burner will lessen the evil, because a smaller quantity of gas will be consumed. If the sulphuretted hydrogen cannot be removed from the gas before it is sent out from the gasworks, a small purifier filled with slaked lime, through which the gas must be passed, should be fixed on the premises. This lime would remove the sulphuretted hydrogen. The spent lime should be removed from time to time, and fresh lime put in its place.