Salt Mixing Problems

[Rog]

I learned something very interesting in this process. my Selbon refractometer I've been using for years, although calibrates perfectly with the solution isn't quite right.

Apparently the Selbon refractometer sold in pretty much all marine aquarium stores is meant for brine solutions, and although close, isn't quite as accurate for seawater specifically. I was at J&L yesterday and tried a new bottle of 35 ppt Selbon calibration fluid on a few other refractometers. Very interesting. The sample that read 1.026 on my freshly calibrated Selbon showed 1.024 on two other refractometers...