Solubility Tests for Electrolytes and NonElectrolytes

The Electrolyte or non Electrolyte solutions :
Objective : role and action of solutions

Soluble and Insoluble Salts
In our discussion up to now, we have considered ionic compounds that dissolve in water; they are soluble salts. However, some ionic compounds do not dissociate into ions in water. They are insoluble salts that remain as solids even in contact with water.
Salts that are soluble in water typically contain at least one of the following ions: Li+, Na+, K+, NH4+, NO3-, or C2H3O2- (acetate). Only a salt containing a soluble cation or anion will dissolve in water. Most salts containing Cl- are soluble, but AgCl, PbCl2, and Hg2Cl2 are insoluble chloride salts. Similarly, most salts containing SO42- are soluble, but a few are insoluble, as shown in(Table 1) Most other salts are insoluble and do not dissolve in water (see Figure 1).
Figure ( 1): If a salt contains a combination of a cation and an anion that are not soluble, that salt is insoluble. For example, combinations of cadmium and sulfide, iron and sulfide, lead and iodide, and nickel and hydroxide do not contain any soluble ions. Thus, they form insoluble salts.

In an insoluble salt, the ionic bonds between its positive and negative ions are too strong for the polar water molecules to break. We can use the solubility rules to predict whether a salt 1a solid ionic compound2 would be expected to dissolve in water.( Table 2) illustrates the use of these rules.
In medicine, the insoluble salt BaSO4 is used as an opaque substance to enhance X-rays of the gastrointestinal tract. BaSO4 is so insoluble that it does not dissolve in gastric fluids