Quote:
Originally Posted by sphelps
Ensuring some salt always remains undissolved insures the salt solution is at max saturation and with constant temperature you can be sure the the salinity of the make up is consistent (max saturation at given temp). You could also in theory measure the salinity and keep it constant however it can be difficult to measure salinity of saturated saltwater and it's easier to just simply look for undissolved salt. It makes other options easier to employ as well. This is of course only important without the use of controllers, a controller eliminates the need to maintain constant salinity in make up water.
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The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.
Think of it this way -- if you dumped a whole lot of salt mix and pushed it to saturation, separated the precipitate out, add more salt mix and repeat -- you would have some expensive NaCl without much else in it.