The solubility groups

It has been found convenient (0. Kamm, 1922) to place organic compounds into seven solubility groups on the basis of  

Group I. Clompounds soluble in both water and ether. 

Group II. Compounds soluble in water, but insoluble in ether. 

Group III. Compounds insoluble in water, but soluble in dilute sodium hydroxide. This group may be further subdivided into Group IIIA—soluble in dilute sodium hydroxide and soluble in dilute sodium bicarbonate and Group IIIB—soluble in dilute sodium hydroxide and insoluble in dilute sodium bicarbonate. 

Group IV. Compounds insoluble in water, but soluble in dilute hydrochloric acid. 

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An outline of the solubility classification procedure is given in Table X 1,5,2, whilst the characteristic features of each of the solubility groups are summarised in Table XI,5,3. 

Memorize the Group 1 hydroxides (hi OH) and the soluble Group 2 hydroxides (OH)2)-LiOH... 

After the unknown is assigned to one of the solubility groups (Fig. 2) on the basis of solubility tests, the possible type should be further narrowed by application of classification tests, e.g., for alcohols, or methyl ketones, or esters. 

To classify a given compound, it may not be necessary to test its solubility in every solvent. Do only those tests that are required to place the compound in one of the solubility groups. Make your observations with care, and proceed in a logical sequence as you make the tests. 

The test is carried out with solvents in the given sequence. Once the solubility group is determined (see below), no more experiments with subsequent solvents are made. If the substance is not soluble in water, its solubility in ether is not tested, but solubility in subsequent solvents is tested immediately. 

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