ABSTRACT
In qualitative tests based on selective precipitation, the identity of the substance in question is verified by ensuring that it gives a precipitate under the defined conditions. In many cases it is a more or less explicit demand of the test that the precipitate have a defined appearance, such as for example a dense gelatinous or crystalline appearance. Whether a substance gives a precipitate in the conditions the tests specify depends on its solubility under these exact conditions and also on the kinetics of the given precipitation. The appearance of a precipitate, apart from the color, is largely determined by its particle size distribution and by its affinity toward the water molecules and ions of the surrounding solution.
