1.1 这些测试方法涵盖了通过2.00mm（10号）筛的土壤pH值的测量。此类测量用于农业、环境、岩土工程和自然资源领域。该测量确定了悬浮在水中的土壤材料的酸度或碱度，以及0.01 M 氯化钙溶液。两种液体中的测量对于完全确定土壤的pH值是必要的。该变量可用于确定土壤矿物质的溶解度和土壤中离子的流动性，并评估土壤植物环境的生存能力。参考文献中对此参数的有用性进行了更详细的讨论 ( 1. 6. ) 2. . 1.2 提供了两种测量土壤pH值的方法。使用的方法应由请求机构指定。当没有指定方法时，应使用方法A。 两种方法都在试验水中和氯化钙溶液中测量pH值。 1.2.1 方法A-- 使用具有pH敏感电极系统的电位计测量pH值。此方法可用于任何应用程序，并且必须在应用程序保证更高分辨率时使用。 1.2.2 方法B-- 使用pH敏感纸测量pH值。然而，这种方法可用于任何应用，因为纸张的分辨率通常较低，它提供了土壤pH值的近似估计，当应用需要更高的分辨率时，不应使用( 附注1 ). 注1: 例如，将灵敏度为最接近1 pH单位的纸张放入4的缓冲溶液中，应指示pH值为4，但它不会指示pH值是4.449还是3.449。 1.3 单位-- 以国际单位制表示的值应被视为标准值。 本标准不包括其他计量单位。 1.4 所有测量和计算值应符合实践中规定的有效数字和四舍五入的指导方针 D6026 . 1.4.1 用于规定如何在标准中收集/记录和计算数据的程序被视为行业标准。此外，它们代表了通常应保留的有效数字。所使用的程序不考虑材料变化、获取数据的目的、特殊目的研究或对用户目标的任何考虑；并且通常的做法是增加或减少报告数据的有效数字以与这些考虑相称。考虑工程数据分析方法中使用的有效数字超出了这些测试方法的范围。 1.5 本标准并不旨在解决与其使用相关的所有安全问题（如果有的话）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 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 土壤的pH值是确定土壤矿物质溶解度、土壤中离子迁移率和评估土壤植物环境生存能力的有用变量。 5.2 pH值测量是在测试水和氯化钙溶液中进行的，因为钙会置换一些可交换的铝。低离子强度通过将溶液的盐浓度设置为更接近土壤溶液中预期的盐浓度来抵消交换平衡的稀释效应。由于释放出更多的铝离子，然后水解，氯化钙溶液中获得的pH值略低于水中测量的pH值。因此，需要两种测量方法来充分确定土壤pH值的特征。 5.3 为了这些试验方法的目的，试样通过2.00mm（10号）筛进行筛分。通过这些测试方法对粒径大于2.0mm的土壤或土壤组分的测量可能无效。如果土壤或土壤颗粒大于2。 如果使用0 mm，则必须在报告中说明，因为结果可能存在显著差异。 注2: 本标准产生的结果的质量取决于执行人员的能力以及所用设备和设施的适用性。符合实践标准的机构 D3740 通常被认为有能力进行合格和客观的测试/取样/检查。可靠的结果取决于许多因素；实习 D3740 提供了一种评估其中一些（但不是全部）因素的方法。

1.1 These test methods cover the measurement of the pH of soils that will pass the 2.00 mm (No. 10) sieve. Such measurements are used in the agricultural, environmental, geotechnical, and natural resources fields. This measurement determines the degree of acidity or alkalinity in soil materials suspended in water and a 0.01 M calcium chloride solution. Measurements in both liquids are necessary to fully define the soil's pH. This variable is useful in determining the solubility of soil minerals and the mobility of ions in the soil and assessing the viability of the soil-plant environment. A more detailed discussion of the usefulness of this parameter is given in Refs ( 1- 6 ) 2 . 1.2 Two methods for measuring the pH of soils are provided. The method to be used shall be specified by the requesting authority. When no method is specified, Method A shall be used. The pH is measured in test water and a calcium chloride solution for both methods. 1.2.1 Method A— The pH is measured using a potentiometer having a pH sensitive electrode system. This method can be used for any application and must be used when the application warrants a higher level of resolution. 1.2.2 Method B— The pH is measured using pH sensitive paper. This method can be used for any application, however, because paper typically has a lower resolution, it provides an approximate estimate of the pH of the soil and should not be used when the application requires a higher level of resolution ( Note 1 ). Note 1: For example, paper with a sensitivity to the nearest 1 pH unit placed into a buffer solution of 4 should indicate a pH of 4, however, it would not indicate if the pH is 4.449 or 3.449. 1.3 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 All measured and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 . 1.4.1 The procedures used to specify how data are collected/recorded and calculated in the standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of these test methods to consider significant digits used in analysis methods for engineering data. 1.5 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. 1.6 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 the soil is a useful variable in determining the solubility of soil minerals, the mobility of ions in the soil, and assessing the viability of the soil-plant environment. 5.2 pH measurements are made in both test water and a calcium chloride solution because the calcium displaces some of the exchangeable aluminum. The low ionic strength counters the dilution effect on the exchange equilibrium by setting the salt concentration of the solution closer to that expected in the soil solution. The pH values obtained in the solution of calcium chloride are slightly lower than those measured in water due to the release of more aluminum ions which then hydrolyses. Therefore, both measurements are needed to fully define the character of the soil's pH. 5.3 For the purpose of these test methods, the test specimens are sieved through a 2.00 mm (No. 10) sieve. Measurements on soils or soil fractions having particle sizes larger than 2.0 mm by these test methods may be invalid. If soil or soil fractions with particles larger than 2.0 mm are used, it must be stated in the report since the results may be significantly different. Note 2: The quality of the result produced by this standard is dependent on the competence of the personnel performing it and the suitability of the equipment and facility used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some, but not all, of those factors.