Can DIY calibration fluid be used to check swing arm hydrometer

[Fieroguy19]

I was wondering if the 35ppt NaCl solution could be used to check a swing arm hydrometer for accuracy.

I am guessing that it will not work since the solution is made for a specific refractive index and not for a certain specific gravity. Is that right?

Thanks

[Randy Holmes-Farley]

Not exactly 35 ppt NaCl, but yes you can do it. I give a recipe here:


Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm