1.1 这些试验方法包括使用玻璃电极作为传感器，通过电测量来测定pH值。两种试验方法如下: 小节 试验方法A-精确实验室测量 8. 到 15 试验方法B-常规或连续测量 16 到 24 1.2 试验方法A包括使用七种标准参考缓冲溶液中的至少两种精确测量水中pH值，以进行仪器标准化。 1.3 试验方法B涵盖了水中pH值的常规测量，尤其适用于连续监测。使用两个缓冲器在受控参数下对仪器进行标准化，但条件的限制性比试验方法A中的限制性小一些。 对于在线测量，另请参阅测试方法 D6569 这提供了更多细节。 1.4 两种测试方法均基于NIST（前身为NBS）标准参考材料建立的pH标度。 2. 1.5 这两种试验方法均不足以测量电导率小于约5μS/cm的水中的pH值。参考测试方法 D5128 和 D5464 . 1.6 仅使用缓冲溶液获得精度和偏差数据。用户有责任确保这些测试方法对未经测试的水类型的有效性。 1.7 以国际单位制表示的数值应视为标准值。 括号中给出的值是英寸-磅单位的数学转换，仅供参考，不被视为标准值。 1.8 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户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。 1.9 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）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》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 水的pH值是一个关键参数，影响微量矿物的溶解度、水形成水垢或引起金属腐蚀的能力，以及水维持生物体的适宜性。它是一个定义的规模，基于缓冲溶液系统 2. 具有指定值。在25°C的纯水中，pH 7.0是中性点，但这随温度和样品的离子强度而变化。 5. 与空气平衡的纯净水的pH值约为5.5，大多数天然未受污染的水的pH值在6到9之间。

1.1 These test methods cover the determination of pH by electrometric measurement using the glass electrode as the sensor. Two test methods are given as follows: Sections Test Method A—Precise Laboratory Measurement 8 to 15 Test Method B—Routine or Continuous Measurement 16 to 24 1.2 Test Method A covers the precise measurement of pH in water utilizing at least two of seven standard reference buffer solutions for instrument standardization. 1.3 Test Method B covers the routine measurement of pH in water and is especially useful for continuous monitoring. Two buffers are used to standardize the instrument under controlled parameters, but the conditions are somewhat less restrictive than those in Test Method A. For on-line measurement, also see Test Method D6569 which provides more detail. 1.4 Both test methods are based on the pH scale established by NIST (formerly NBS) Standard Reference Materials. 2 1.5 Neither test method is considered to be adequate for measurement of pH in water whose conductivity is less than about 5 μS/cm. Refer to Test Methods D5128 and D5464 . 1.6 Precision and bias data were obtained using buffer solutions only. It is the user's responsibility to assure the validity of these test methods for untested types of water. 1.7 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard. 1.8 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. 1.9 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 The pH of water is a critical parameter affecting the solubility of trace minerals, the ability of the water to form scale or to cause metallic corrosion, and the suitability of the water to sustain living organisms. It is a defined scale, based on a system of buffer solutions 2 with assigned values. In pure water at 25°C, pH 7.0 is the neutral point, but this varies with temperature and the ionic strength of the sample. 5 Pure water in equilibrium with air has a pH of about 5.5, and most natural uncontaminated waters range between pH 6 and pH 9.