| abstract |
A steady stream of high purity gas, e.g. for use in semi-conductor processing, contng. 10-8 p.b.w. of water, from a standard industrial reservoir (e.g. type C25), contng. unrefined commercial gas esp. N2, is produced by providing an outlet pipe of stainless steel (which may be sheathed in copper) dipping below the surface of the liq. gas, so that solid impurities, floating or sedimented, are eliminated. Outlet pipe transfers heat of evaporation by conduction, and has a valve to regulate gas flow. Pressure in reservoir is controlled, pref. by a relief valve operating at a preset pressure level. No supplementary cryogenic or chemical traps are necessary, and short connecting pipes with low dead space may be used. |