1.1 本试验方法包括测定水中总二氧化硅。 1.2 此测试方法适用于25 μg/L至250 μg/L二氧化硅（以二氧化硅计） 2. 更高的浓度可以通过减少等分试样的体积来确定（参见 注释6 ). 浓度范围不应通过稀释来扩大。 1.3 该试验方法测定总二氧化硅，不区分可溶性和不溶性二氧化硅。 1.4 此测试方法仅在试剂水上进行测试。用户有责任确保测试方法对其他基质水的有效性。 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 有必要控制锅炉给水和锅炉水中的二氧化硅，以最大限度地减少结垢硅酸盐的形成，从而降低锅炉中的传热。蒸汽中二氧化硅的挥发和携带可能会导致涡轮机叶片上形成坚硬的玻璃状硅质沉积物，从而降低涡轮机效率。 5.2 未通过锅炉水预处理过程去除的胶体二氧化硅可能溶解在锅炉中，从而有助于锅炉中溶解二氧化硅的浓度。溶解二氧化硅和总二氧化硅都值得关注。

1.1 This test method covers the determination of total silica in water. 1.2 This test method is applicable in the range from 25 μg/L to 250 μg/L of silica as SiO 2 . Higher concentrations may be determined by decreasing the aliquot volume (see Note 6 ). Concentration range should not be extended by dilution. 1.3 This test method determines total silica, and does not distinguish between soluble and insoluble forms. 1.4 This test method was tested on reagent water only. It is the user's responsibility to assure the validity of the test method for waters of other matrices. 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 Control of silica in boiler feedwater and boiler water is necessary to minimize the formation of scale-forming silicates that decrease heat transfer in the boiler. Volatilization and carryover of silica with the steam may cause hard, glassy siliceous deposits to form on turbine blades that reduce turbine efficiency. 5.2 Colloidal silica that is not removed by boiler water pretreatment processes may be solubilized in the boiler and thus contribute to the dissolved silica concentration in the boiler. Both dissolved and total silica are of interest.