Slow dissolution of the borosilicate container of triple-point-of-water (TPW) cell is widely recognized as the main cause of long-term drift in observed triple point temperature. We add to the available experimental data a comparison of two large batches of TPW cells (67 cells in total) of various ages (from 1 year to 64 years), manufacturers (NRC, VSL, Fluke, Isotech, etc.), and materials (borosilicate glass and fused-silica) which was undertaken in 2018. After measuring the TPW temperatures realized by all 67 cells, 12 borosilicate cells were opened and their water was analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in order to correlate their impurity content with their respective age and their realized TPW temperature. No direct correlation was observed between the TPW cells age/impurity content and their measured triple-point temperature for neither borosilicate cells nor fused silica cells (Pearson’s correlation coefficient rxy is within the range −0.60 ≤ rxy ≤ +0.40 for all the pairs considered). For fused-silica cells, the results indicate that after the isotopic variation in the water source is taken into account, the long-term drift due to the dissolution of glass envelope, if any, is negligibly small: (+0.4(±0.6) μK·yr reported herein). Given that all the fused-silica cells realize the TPW temperature within 100 μK of NRC and VSL national reference cells and since the analyzed time period of 15 years is equal to the average lifespan of a TPW cell, we conclude that fused-silica TPW cells are superior to those made from borosilicate glass.

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关于三相水电池的长期稳定性

水三相点 (TPW) 电池的硼硅酸盐容器的缓慢溶解被广泛认为是观察到的三相点温度长期漂移的主要原因。我们在可用的实验数据中添加了对不同年龄（从 1 年到 64 年）、制造商（NRC、VSL、Fluke、Isotech 等）和材料的两大批次 TPW 电池（总共 67 个电池）的比较（硼硅玻璃和熔融石英），于 2018 年进行。 在测量了所有 67 个电池实现的 TPW 温度后，打开 12 个硼硅酸盐电池并通过电感耦合等离子体质谱 (ICP-MS) 分析它们的水，以便将它们的杂质含量与它们各自的年龄和它们实现的 TPW 温度相关联。对于硼硅酸盐电池和熔融石英电池，在 TPW 电池老化/杂质含量与其测量的三相点温度之间未观察到直接相关性（对于所有考虑的对，Pearson 相关系数 rxy 在 -0.60 ≤ rxy ≤ +0.40 的范围内） . 对于熔融石英电池，结果表明，在考虑水源的同位素变化后，由于玻璃外壳溶解引起的长期漂移（如果有的话）小到可以忽略不计：(+0.4(±0.6) μK·yr 在此报告）。鉴于所有熔融石英电池都实现了 100 μK 以内的 NRC 和 VSL 国家参考电池的 TPW 温度，并且由于 15 年的分析时间段等于 TPW 电池的平均寿命，我们得出结论，熔融石英 TPW 电池优于由硼硅玻璃制成的那些。