To reduce soluble impurities and to produce simply and economically by dissolving a gas purified by being contacted with pure water in advance into a cleaning liquid.
A gas purified by being contacted with pure water in advance is dissolved into a cleaning liquid. Besides pure water and ultrapure water, an acidic cleaning liquid in which hydrochloric acid and others are added into pure water or ultrapure water, an alkaline cleaning water containing added with ammonia and others, an oxidizing cleaning liquid added with hydrogen peroxide and others, and a reducing cleaning liquid added with a hydrogen sulfate and others are used as the cleaning liquid. Ozone, hydrogen, oxygen, carbon dioxide, chlorine, argon, and others is used as the gas to be dissolved. The gas is led to a porous plate 3 installed in the bottom part of a water bath container 2 through raw material gas piping 1 and released into pure water as bubbles. The gas in which impurities are dissolution-removed is sent through a purifying gas piping 4. A pure water inlet 5 and water outlet 6 are formed in the container 2 for the renewal of water.
IDA JUNICHI
MIZUNIWA TETSUO
OSAWA KIMINOBU
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