Randy Holmes-Farley
Well-Known Member
Here's the plan:
I will bring two bottles of a NaCl standard that should match the refractive index of 35 ppt seawater, and a bottle of DI water. Greg Hiller will bring a nominal 35 ppt actual standard seawater sample. I'll bring some labeled pipettes to prevent mix ups. I'll also bring some "answer" sheets so we can keep track of the values and refractometer brands.
We will calibrate each refractometer against the DI water, then test them all against both the NaCl and seawater standard (assuming Greg has enough of the latter).
The questions to be answered are:
1. Do all refractometers get the same values for each standard, regardless of what that value ends up being? Are some off from the others?
2. Do the refractometers get the "correct" value for the seawater standard?
3. Do the refractometers get the "correct" value for the sodium chloride standard?
This information can be used to determine:
A. Whether refractometers frequently used in the hobby need only DI water calibration to give consistent values (to within what uncertainty?), or whether a different calibration point is more useful.
B. Whether the NaCl standard that I have made and discussed in a previous article is adequate for refractometers in use in the hobby.
This is the article mentioned above:
Reef Aquarium Salinity: Homemade Calibration Standards
http://www.reefkeeping.com/issues/2004-06/rhf/index.php
I will bring two bottles of a NaCl standard that should match the refractive index of 35 ppt seawater, and a bottle of DI water. Greg Hiller will bring a nominal 35 ppt actual standard seawater sample. I'll bring some labeled pipettes to prevent mix ups. I'll also bring some "answer" sheets so we can keep track of the values and refractometer brands.
We will calibrate each refractometer against the DI water, then test them all against both the NaCl and seawater standard (assuming Greg has enough of the latter).
The questions to be answered are:
1. Do all refractometers get the same values for each standard, regardless of what that value ends up being? Are some off from the others?
2. Do the refractometers get the "correct" value for the seawater standard?
3. Do the refractometers get the "correct" value for the sodium chloride standard?
This information can be used to determine:
A. Whether refractometers frequently used in the hobby need only DI water calibration to give consistent values (to within what uncertainty?), or whether a different calibration point is more useful.
B. Whether the NaCl standard that I have made and discussed in a previous article is adequate for refractometers in use in the hobby.
This is the article mentioned above:
Reef Aquarium Salinity: Homemade Calibration Standards
http://www.reefkeeping.com/issues/2004-06/rhf/index.php
