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通常采用电阻率、粒子大小和细菌数目来衡量高纯水的纯度。目前主要以电阻率为标准,它的单位以兆欧·厘米来表示。水在25℃时的最高电阻率为18.3兆欧·厘米。水质的好坏与电阻率的高低成正比。 按电阻率高低,可将纯水分为四类: (1)软化水:硬度为0.1～5°之间; (2)脱盐水:25℃时电阻率为0..1～1兆欧·厘米; (3)纯水:25℃时水的电阻率为1～10兆欧·厘米; (4)高纯水:25℃时水的电阻率为10兆欧·厘米以上。 由于用途不同而对水的质量的要求也不同。如,对于集成电路的生产用水,其要求是:电阻率为18～19兆欧·厘米,粒子尺寸<0.45微米,细菌数为0～10个/毫升。
Resistivity, particle size and number of bacteria are commonly used to measure the purity of highly purified water. Currently mainly based on the resistivity, its unit is expressed in megohms cm. The highest resistivity of water at 25 ° C is 18.3 megohm · cm. The quality of water is proportional to the level of resistivity. According to the resistivity level, the pure water can be divided into four categories: (1) demineralized water: the hardness is between 0.1 and 5 °; (2) desalinated water: the resistivity is 0..1 to 1 megohm at 25 ° C. Cm; (3) Pure water: the resistivity of water at 25 ℃ is 1 ~ 10 megohm · cm; (4) High-purity water: the resistivity of water at 25 ℃ is above 10 Megohm · cm. Due to different purposes and the quality of the water requirements are different. For example, the production of water for integrated circuits, its requirements are: resistivity of 18 ~ 19 megohm · cm, particle size <0.45 microns, the number of bacteria is 0 ~ 10 / ml.