1.1 本试验方法包括通过光学传感器进行电位检测，通过滴定法测定水中硬度。本试验方法适用于不含会使钙或镁复合的化学物质的水域。该测试方法的检测下限约为2 mg/L至5 mg/L（以CaCO计） 3. ; 可以通过样品稀释将上限扩展到所有浓度。通过这种测试方法，可以区分由钙离子引起的硬度和由镁离子造成的硬度。 1.2 本试验方法适用于无色和有色水样，包括地下水、地表水、废水和饮用水。 1.3 以国际单位制表示的数值应视为标准。本标准不包括其他计量单位。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 水中的硬盐，尤其是钙和镁，是管道结垢的主要原因，管道结垢通常会因堵塞或传热损失或两者兼有而导致故障和工艺效率损失。 5.2 硬度是由任何多价阳离子引起的，但Ca以外的阳离子除外 +2 和Mg +2 很少有超过微量的存在。 硬度一词最初适用于难以清洗的水；它指的是水的浪费肥皂的特性。对于大多数普通的碱性水，这些肥皂浪费特性与钙和镁含量直接相关。

1.1 This test method covers the determination of hardness in water by titration with potentiometric detection via optical sensor. This test method is applicable to waters that are free of chemicals that will complex calcium or magnesium. The lower detection limit of this test method is approximately 2 mg/L to 5 mg/L as CaCO 3 ; the upper limit can be extended to all concentrations by sample dilution. It is possible to differentiate between hardness due to calcium ions and that due to magnesium ions by this test method. 1.2 This test method is applicable to both colorless and colored water samples including groundwater, surface water, wastewater, and drinking water. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Hardness salts in water, notably calcium and magnesium, are the primary cause of tube and pipe scaling, which frequently causes failures and loss of process efficiency due to clogging or loss of heat transfer, or both. 5.2 Hardness is caused by any polyvalent cations, but those other than Ca +2 and Mg +2 are seldom present in more than trace amounts. The term hardness was originally applied to water in which it was hard to wash; it referred to the soap-wasting properties of water. With most normal alkaline water, these soap-wasting properties are directly related to the calcium and magnesium content.