Isotech 17724 Mercury Triple Point Cell
- Uncertainty 0.000200°C
- Rugged Stainless Steel Construction
- 7N Pure
The Isotech Mercury Triple Point Cell is a primary ITS‑90 standard with a triple point of –38.8344 °C, designed for laboratories requiring the highest confidence in low‑temperature metrology. Housed in a rugged, sealed stainless‑steel enclosure, the cell allows the mercury triple point to be realised safely, reliably and with exceptional reproducibility. With an uncertainty of just 0.000200 °C (0.2 mK), it is among the most accurate fixed‑point standards available today. Its 7N‑purity metal, proven construction and decades of international use make it a reference trusted by national laboratories worldwide.
Developed with NIST — a legacy of precision
The modern embodiment of the Mercury Triple Point Cell was developed more than twenty years ago through close collaboration between Henry Sostmann and Dr. Furukawa of the former NBS (now NIST).
Isotech continues to manufacture the cells to the original specifications:
- > identical physical dimensions
- > identical materials
- > identical metal purity
- > identical supplier
The mercury is quadruple‑distilled, leaving only 10–15 parts per billion of impurities. Even after twenty years, opened cells have been found to remain >99.99995% pure, demonstrating the long‑term stability of the design.
In international intercomparisons, Isotech cells have consistently performed within the uncertainty limits of national laboratories.
Operation and plateau realisation
The Mercury Cell can be realised in two ways:
- In an Isotech stirred liquid bath, such as the Hydra or 915, producing plateau durations of up to one week.
- In the dedicated Mercury Triple Point Apparatus, which avoids the need for liquids and is widely used in NMIs and commercial calibration labs.
Both methods provide a stable, flat and highly reproducible plateau.
Construction and durability
The cell is built entirely from stainless steel, ensuring:
- > mechanical robustness
- > safe containment of the mercury
- > long‑term reliability and transport safety
The metal column has a depth of 200 mm, ideal for immersing precision thermometers.
The Isotech Mercury Triple Point Cell is a highly accurate, stable and durable ITS‑90 fixed‑point standard. With its 7N‑purity metal, proven design and decades of successful international use, it is an essential reference for laboratories requiring absolute confidence in low‑temperature calibration.
