What is the most reliable salinity test process?

[Jan]

OK, re-reading the article in ReefKeeper Magazine, I found this passage:

...recalibration of a refractometer with a slope error...what happens when adjusting the calibration screw so that the specific gravity of a 35 ppt seawater standard (with a known specific gravity of 1.0264) really reads 1.0264...the refractometer is then good to go at specific gravity values near 1.0264 (say, 1.020 to 1.030), but it is no longer accurate at a specific gravity of 1.000 (freshwater; Figure 19).

So the fact that my refractometer doesn't read fresh water at 0 anymore should not be a problem...I think...

 

[Boomer]

Yes, that is correct. Just take that Pinpoint 53mS solution and put it on the refract and cal it to read 1.0264 or 35 ppt. Forget about RO/DI.