"Rocco Moretti" wrote in message
...
Bill Stock wrote:

I gather these "dissolvability" numbers are cumulative and not specific
to each chemical? Is the cumulative effect straight line or does it
depend on the chemicals being dissolved.

In chemistry the amount of a salt that can dissolve is sometimes expressed
as a solubility product constant. That is, at saturation, multiplying the
concentration of the negative ion by the concentration of the positive ion
gives a constant value. (What the value is depends on which salt you're
talking about.)

To a first approximation, the value of the constant does not depend on
what other salts are dissolved in solution. For example, the amount of K+
in a saturated KNO3 + NaCl solution is the same as the amount of K+ in a
saturated KNO3 solution without the sodium chloride.

However, if the two salts share the same ion, you get what's called the
common ion effect - you increase the total amount of the shared ion, which
reduces the amount of the other ions which can be dissolved, relative to
dissolving each one individually. I've seen it happen with concentrated
HCl added to concentrated NaCl - the Cl concentration got too high, and
NaCl crashed out of solution.

Thanks Rocco, so my MgSO4+7H2O should not reduce the solubility of my KCL if
I understand you correctly. This does not seem to be what I'm experiencing
though, as I'm achieving no where near the solubility numbers in Chuck's
calculator. Perhaps there is some CL in the Plantex mixture, which is
causing the KCL to precipitate.