Presence of Multiple Solutes
The aqueous solubility of nonelectrolytes is nearly always affected in some
way by the addition of an electrolyte. Salting-out
is the precipitation of organic solutes from aqueous solution by the
addition of an electrolyte or salt. This is attributed to competition between
solute molecules for the solvent and is dependent upon the size and valence
of the ion. Salting-in is the increase
in solubility of an organic solute upon addition of an electrolyte. The
mechanism of this phenomenon is poorly understood and it is rarely encountered.
An example is with the group of proteins called globulins which are more
soluble in dilute salt solutions than in water. Complex ion
formation occurs when an insoluble solute reacts with a soluble
substance to form a soluble complex. An example is the addition of the
soluble potassium iodide (KI) to the insoluble iodine molecule (I2) to
form a soluble triiodide complex (KI3).