I know that for a particular, immiscible solute, there is a limit on how much of it can be dissolved in a solvent at a given temperature. However, I was wondering if there is only so much "total solute" that a given solvent can dissolve. As a simple example, suppose you saturate water with salt, then start dissolving sugar into it. Does the fact that it is saturated with salt limit how much sugar it can dissolve? My mental image is one of each water molecule being able to suport only so many solvation structures, regardless of the chemicals participating in the structure.
If you speak about solubility, you are out of domain of simple approximations and the only correct answer is the experiment. For the example given, see http://dx.doi.org/10.1111/j.1365-2621.1992.tb01192.x
The problem is the difficulty to quantify the effect of temperature, which is very important here.