9. No word which is the commonly used and accepted name of any single chemical element or single chemical compound (as distinguished from a mixture) shall be registered as a trade mark in respect of a chemical substance or preparation, and any such registration shall, notwithstanding anything in section 24, be deemed for the purposes of section 46 to be an entry made in the register without sufficient cause or an entry wrongly remaining on the register, as the circumstances may require: Provided that this section shall not apply to a word which is used to denote only a brand or make of the element or compound as made by the proprietor or a registered user of the trade mark, as distinguished from the element or compound as made by others, and in association with a suitable name or description open to the public use.