Randy Holmes-Farley
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Reef Chemistry Question of the Day #264
Most reef aquarists that use refractometers are aware that the refractive index changes with temperature. Some handheld refractometers account for temperature by employing a bimetal strip inside them. This bimetal strip expands and contracts as the temperature changes. The bimetal strip is attached to the optics inside the refractometer, moving them slightly as the temperature changes. This movement is designed to exactly cancel temperature’s effects on refractive index.
Suppose that you have a refractometer that DOES NOT have such a temperature correction, and is properly made to read seawater salinity at 20 degrees C (68 degrees F).
If you measure salinity at 30 degrees C (86 degrees F), the reading you get from the refractometer will incorrectly give approximately what value when the water is really 35 ppt salinity?
A. 30 ppt
B. 34.1 ppt
C. 35.9 ppt
D. 40 ppt
Pick the closest choice to what you think the answer is.
Good luck!
.
Most reef aquarists that use refractometers are aware that the refractive index changes with temperature. Some handheld refractometers account for temperature by employing a bimetal strip inside them. This bimetal strip expands and contracts as the temperature changes. The bimetal strip is attached to the optics inside the refractometer, moving them slightly as the temperature changes. This movement is designed to exactly cancel temperature’s effects on refractive index.
Suppose that you have a refractometer that DOES NOT have such a temperature correction, and is properly made to read seawater salinity at 20 degrees C (68 degrees F).
If you measure salinity at 30 degrees C (86 degrees F), the reading you get from the refractometer will incorrectly give approximately what value when the water is really 35 ppt salinity?
A. 30 ppt
B. 34.1 ppt
C. 35.9 ppt
D. 40 ppt
Pick the closest choice to what you think the answer is.
Good luck!
.