VSMOW Triple Point of Water Cells: Borosilicate versus Fused-Quartz

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VSMOW Triple Point of Water Cells: Borosilicate versus Fused-Quartz (335.89 KB)

To investigate an ideal container material for the triple point of water (TPW) cell, and reduce the influence to the triple-point temperature due to the deviation of the isotopic composition of the water, we developed and tested both borosilicate and fused-quartz glass shelled TPW cells with isotopic composition substantially matching that of Vienna Standard Mean Ocean Water (VSMOW). Through a specially designed manufacturing system, the isotopic composition, δD and δ¹⁸O, of the water in the TPW cell could be controlled within ±10‰ (per mil) and ±1.5‰ respectively, resulting in control of the isotopic temperature correction to better than ±8 μK. Through an ampoule attached to the cell, the isotopic composition of the water in the cell could be analyzed individually. After manufacture, the initial triple-point temperature of the two types of cell were measured and compared to assess the quality of the cells and manufacturing process. Cells fabricated with the new system agree to within 50 μK. Two innovatively-designed borosilicate and fused-quartz TPW cells were made, each with six attached ampoules. We removed one ampoule every six months to track any changes in purity of the water over time.