Sper Scientific* Mason's Hygrometer Red Liquid - Each

One thermometer bulb is kept constantly wet by a siphon reservoir while the other gives a dry temperature reading. Humidity is obtained by comparing the two readings on the enclosed chart. The red liquid masons hygrometer uses a safe and easy to read red liquid in place of the usual mercury. Dual scales of -10 to 50°C and 10 to 120°F. 5 year warranty.
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