Log Ksp is the exponent to which one would have to raise 10 to in order to regenerate the product of multiplying the concentrations of all ions in solution to get the solubility product constant, including raising the concentration to the power of the molar ratio for any chemical reaction causing solution. Solubility product constants are usually determined on saturated solutions in which there is some solid that is not dissolved in solution. Gold's value for its sulfide, binding chemical compounds like vitaletheine, is -54.5. The more negative the number, the worse these metals can be for us since they bind up the sulfur metabolism needed to properly balance our bodies. These are logarithmic numbers, so the Ksp is actually 10 raised to the power of these.