Classification of cations metal ions into analytical groups

The group reagents used for the classification of most common cations are hydrochloric acid, hydrogen sulphide, ammonium sulphide, and ammonium carbonate. Classification is based on whether a cation reacts with these reagents by the formation of precipitates or not. It can therefore be said that classification of the most common cations is based on the differences of solubilities of their chlorides, sulphides, and carbonates. 

The five groups of cations and the characteristics of these groups are as follows  

Group / Cations of this group form precipitates with dilute hydrochloric acid. Ions of this group are lead, mercury(I), and silver. 

Group III Cations of this group do not react either with dilute hydrochloric acid, or with hydrogen sulphide in dilute mineral acid medium. However they form precipitates with ammonium sulphide in neutral or ammoniacal medium. Cations of this group are cobalt(II), nickel(II), iron(II), iron(III), chromium(III), aluminium, zinc, and manganese(II). 

Group IV Cations of this group do not react with the reagents of Groups I, 

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Classification of cations (metal ions) into analytical groups... 

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