That gives me some insight as to what happens, but since there are obvious shifts in composition, I can't really base a whole lot on it.
I'm getting conflicting information from elsewhere too. It seems my best approach may be with samples until I get what I'm looking for?
I suppose the answer to my original question is 'yes', but now it's a matter of figuring out the optimal mixture.
From experimentation with the freezer and a thermometer (with just fresh water ATM), I'm estimating my ideal bottom line temperature to be about 0F (-17.78C). Targeting too much colder than that really begins to show a strain on the freezer (and may not even completely freeze), too much warmer than that and it would be a waste of time.
I'm noticing from the chart in the PDF that the heat capacity drops as the ratio of 'salt' to water gets higher, while the latent heat drops only slightly. This leads me to believe that the 'holding power' at a lower temperature is worth the effort, but it 'burns' it quicker by absorbing the heat at a lower temperature.
The result being that if a given volume of pure water holds the temperature at 32F for, say 1 hour, the same volume of salt water might only be able to hold 0F for 45 minutes (made up times to illustrate the point).
Not that I would not be able to work with that, but I want to make sure... Am I on target here?
Steve