总硬度主要是指溶在水中的钙盐、镁盐类的含量,是水质的主要指标之一[1]。GB 5749-2006[2]规定生活饮用水的总硬度限量为<450mg/L。当测定结果在临界值附近时,只有考虑测定的不确定度,判定的结果才是完整的和有意义的,本文根据《中华人民共和国国家计量技术规范-测量不确定度评定与表示》(JJF-1059-1999)[3]和《化学分析中不确定度的评估指南》[4],对生活饮用水中总硬 The total hardness is mainly refers to the dissolved in water, calcium, magnesium content, is one of the main indicators of water quality [1]. GB 5749-2006 [2] provides that the total hardness of drinking water limited to <450mg / L. When the measurement result is near the critical value, the result of the judgment is complete and meaningful only by considering the uncertainty of the measurement. According to “National Metrology Specifications of the People’s Republic of China - Assessment and Expression of Measurement Uncertainty” (JJF -1059-1999) [3] and “Guidelines for the Evaluation of Uncertainty in Chemical Analysis” [4], the total hardness of drinking water