1.1 本试验方法包括使用钼蓝法（也称为杂多蓝法）通过比色分析在线测定水中可溶性二氧化硅。 1.2 本试验方法适用于二氧化硅浓度在0.5以内的水中二氧化硅的测定 ppb至5000 μg/L）。 1.3 本试验方法包括可溶性二氧化硅二氧化硅的测定 2. （二氧化硅）或水中的硅酸盐。可溶性二氧化硅化合物被认为是钼酸盐反应性二氧化硅。本试验方法不包括胶体或聚合二氧化硅的测定，其被认为是非钼酸盐反应性二氧化硅。 1.4 本试验方法不包括水中二氧化硅的实验室或取样测量。 参考测试方法 D859天 . 1.5 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。 1.6 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。 1.7 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 硅是一种准金属，是地壳中含量第二丰富的元素。各种形式的二氧化硅（二氧化硅 2. )在石英、沙子和岩石中发现。这些岩石的降解导致在天然水中发现二氧化硅。天然水中的二氧化硅可以是离子二氧化硅、硅酸盐、胶体或悬浮颗粒。 5.2 升高的温度和压力会导致水中的二氧化硅蒸发并形成沉积物或水垢。二氧化硅的水垢沉积物将覆盖发电厂使用的锅炉和涡轮叶片。二氧化硅水垢的存在会影响金属的传热能力。在半导体工业中，当去离子水用作制造晶片的冲洗剂时，需要去除二氧化硅。 5.3 二氧化硅通常通过使用阴离子交换树脂的脱盐、蒸馏、反渗透或石灰软化过程中的沉淀来去除。二氧化硅的在线测量是试图获得和监测超纯水的行业实验室分析的首选方法。由于二氧化硅是最早突破阴离子交换树脂的物种之一，因此经常使用在线二氧化硅监测来确定阴离子或混合树脂床的再生需求。

1.1 This test method covers the on-line determination of soluble silica in water by colorimetric analysis using the molybdenum blue method, also known as the heteropoly blue method. 1.2 This test method is applicable for silica determination in water with silica concentrations within 0.5 ppb to 5000 ppb (μg/L). 1.3 This test method covers the determination of soluble silica SiO 2 (silicon dioxide) or silicates in water. Soluble silica compounds are considered molybdate reactive silica. This test method does not cover the determination of colloidal or polymeric silica, which is considered non-molybdate reactive silica. 1.4 This test method does not cover the laboratory or grab sample measurement of silica in water. Refer to Test Method D859 . 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 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. 1.7 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 Silicon (Si), a metalloid, is the second most abundant element in the earth’s crust. Various forms of silica (silicon dioxide SiO 2 ) are found in quartz, sand, and rocks. The degradation of these rocks results in silica found in natural waters. Silica in natural waters can be found as ionic silica, silicates, colloidal or suspended particles. 5.2 Elevated temperatures and pressure can cause silica in water to vaporize and form deposits or scale. Scale deposits of silica will coat boilers and turbine blades used in power plants. The presence of silica scale affects the ability of metals to transfer heat. Silica needs to be removed when deionized water is used as a rinse for manufacturing wafers in the semiconductor industry. 5.3 Silica is commonly removed by demineralization using anion exchange resins, distillation, reverse osmosis or precipitation in a lime softening process. The on-line measurement of silica is the preferred method to laboratory analyses for industries trying to obtain and monitor ultra-pure water. Since silica is one of the first species to breakthrough anion exchange resins, on-line silica monitoring is frequently used to determine the need for regeneration of an anion or mixed resin bed.