Isotech 17725 Mercury Triple Point Apparatus

The Isotech 17725 Mercury Triple Point Apparatus is a purpose‑designed, fully self‑contained system for realising the mercury triple point (–38.8344 °C). Unlike traditional liquid‑bath methods, this apparatus uses mechanical refrigeration to provide a clean, safe and highly stable environment for operating mercury fixed‑point cells. Developed specifically for the Isotech Mercury Cell, the system combines strong cooling performance, precise temperature control and a rugged construction. With more than 35 years of successful use in national metrology institutes, it has become a trusted standard for laboratories requiring the highest accuracy.

Designed for convenience, safety and reproducibility

The apparatus includes a main well for one mercury cell and two auxiliary wells for pre‑chilling thermometers. The cryostat temperature is adjustable from –36 °C to –42 °C, allowing controlled melt and freeze cycles. The refrigeration system has enough capacity to bring a cell to operating temperature in about one hour. Once stabilised, the system can cool at approximately 1 K/min and heat at 2 K/min, enabling rapid but controlled temperature transitions without stressing the cell. All temperature control is achieved through refrigerant‑flow regulation, an inherently fail‑safe method that ensures stable and reliable operation.

Modern control and connectivity

While the mechanical design has a long and proven history, the control system has been fully updated. The apparatus now features:

• > a large colour display with clear graphical output
• > an Ethernet interface for remote monitoring
• > a USB host for copying programs and exporting heat‑up/cool‑down history
• > a programmable mode for switching between melt and freeze conditions

These enhancements make the system both user‑friendly and fully compatible with modern laboratory workflows.

Proven performance in primary laboratories

The Mercury Triple Point Apparatus has been relied upon by national laboratories for more than three decades. Its stable thermal environment and safe, liquid‑free operation make it ideal for producing long, flat plateaus of 8 to 12 hours, essential for high‑accuracy ITS‑90 calibration. When used with the Isotech Mercury Cell, the system achieves an uncertainty of 0.2 mK, placing it among the most accurate mercury fixed‑point systems available.

The Isotech 17725 Mercury Triple Point Apparatus provides a safe, liquid‑free and exceptionally stable method for realising the mercury triple point. With strong cooling performance, modern control features and decades of proven reliability, it is an essential tool for laboratories requiring the highest precision in low‑temperature ITS‑90 calibration.