1.1 这些试验方法 2. 涵盖所有类型水的酸碱度测定。三种试验方法如下: 小节 试验方法A（电位滴定） 7. 到 15 试验方法B（电位滴定法或变色滴定法） 16 到 24 试验方法C（氢后变色滴定 过氧化物氧化和沸腾） 25 到 33 1.2 在所有这些试验方法中，通过标准碱（酸度）或酸（碱度）滴定法中和水中因溶质解离或水解而存在的氢或羟基离子。在这三种程序中，测试方法A最为精确。它用于绘制电位滴定曲线（有时称为pH曲线），该曲线定义了样品的酸碱度，并指示了拐点和缓冲能力（如有）。此外，可以根据任何特定的pH值来确定酸度或碱度。 其他两种方法用于根据内部指示剂的颜色变化或pH计测量的等效终点来确定相对于预先指定终点的酸度或碱度。它们适用于常规控制目的。 1.3 当滴定到特定终点时，终点的选择将需要仔细分析滴定曲线、成分的任何预期变化对滴定曲线的影响、水的预期用途或处置的知识，以及所涉及过程控制的特征。虽然拐点（pH值快速变化）通常是准确分析样品成分和获得最佳精度的首选，但在某些应用中，使用拐点进行过程控制可能会导致化学处理或过程控制中出现重大错误。当滴定到由实际考虑决定的选定终点时( 1. )只能测量水的实际中和能力的一部分，或( 2. )在达到最佳酸度或碱度条件时，实际上可能会超过该容量。 1.4 每个试验方法中都提供了范围部分作为指南。分析员有责任确定这些测试方法对每个矩阵的可接受性。 1.5 停止使用以前的试验方法C（比色滴定）和D（煮沸后变色滴定）。提到 附录X4 以获取历史信息。 1.6 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.7 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和健康实践，并确定监管限制的适用性。 ====意义和用途====== 4.1 酸度和碱度测量用于帮助确定化学处理水平，以控制水垢、腐蚀和其他不利的化学平衡。 4.2 酸碱度对于确定某些金属的溶解度、某些金属的毒性和某些水的缓冲能力至关重要。

1.1 These test methods 2 cover the determination of acidity or alkalinity of all types of water. Three test methods are given as follows: Sections Test Method A (Electrometric Titration) 7 to 15 Test Method B (Electrometric or Color-Change Titration) 16 to 24 Test Method C (Color-Change Titration After Hydrogen Peroxide Oxidation and Boiling) 25 to 33 1.2 In all of these test methods the hydrogen or hydroxyl ions present in water by virtue of the dissociation or hydrolysis of its solutes, or both, are neutralized by titration with standard alkali (acidity) or acid (alkalinity). Of the three procedures, Test Method A is the most precise and accurate. It is used to develop an electrometric titration curve (sometimes referred to as a pH curve), which defines the acidity or alkalinity of the sample and indicates inflection points and buffering capacity, if any. In addition, the acidity or alkalinity can be determined with respect to any pH of particular interest. The other two methods are used to determine acidity or alkalinity relative to a predesignated end point based on the change in color of an internal indicator or the equivalent end point measured by a pH meter. They are suitable for routine control purposes. 1.3 When titrating to a specific end point, the choice of end point will require a careful analysis of the titration curve, the effects of any anticipated changes in composition on the titration curve, knowledge of the intended uses or disposition of the water, and a knowledge of the characteristics of the process controls involved. While inflection points (rapid changes in pH) are usually preferred for accurate analysis of sample composition and obtaining the best precision, the use of an inflection point for process control may result in significant errors in chemical treatment or process control in some applications. When titrating to a selected end point dictated by practical considerations, ( 1 ) only a part of the actual neutralizing capacity of the water may be measured, or ( 2 ) this capacity may actually be exceeded in arriving at optimum acidity or alkalinity conditions. 1.4 A scope section is provided in each test method as a guide. It is the responsibility of the analyst to determine the acceptability of these test methods for each matrix. 1.5 Former Test Methods C (Color-Comparison Titration) and D (Color-Change Titration After Boiling) were discontinued. Refer to Appendix X4 for historical information. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 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 and health practices and determine the applicability of regulatory limitations prior to use. ====== Significance And Use ====== 4.1 Acidity and alkalinity measurements are used to assist in establishing levels of chemical treatment to control scale, corrosion, and other adverse chemical equilibria. 4.2 Levels of acidity or alkalinity are critical in establishing solubilities of some metals, toxicity of some metals, and the buffering capacity of some waters.