| http://www.w3.org/ns/prov#value | - For these reasons, numerous attempts have been made at great expense to devise can filling and sealing equipment which can be automatically operated in a vacuum, or in a chamber filled with inert gas such as carbon dioxide or nitrogen, but so far as I am aware, such equipment has not been made commercially successful, and, in any event, it is extremely expensive and diihcult to control.
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