Purified water is a kind of water which has been removed almost all the conducting medium, colloid and organic matters (including bacteria), etc. The conductivity of purified water is about 0. 1-0. 55Μs/cm, and its resistivity (25℃) is about more than 10mω·cm, and its tds is about less than 0. 1Mg/l. In theory, the conductivity of purified water is 0. 055Μs/cm, and its resistivity (25℃) is 18. 3Mω·cm.