No lab work was done with this group due to the smell and toxicity problems associated with sulfides. 4 Aluminum Group Analysis These metals are traditionally separated from solution as metal sulfides or hydroxides in basic solution. Sulfide precipitations will not be performed with this group but lab work will be done to look at physical and chemical properties of these cations. Several of the metals in this group form colored solutions which make identification easier. Nickel forms the very diagnostic red-pink complex with dimethylglyoxime and also forms a blue colored complex ion with ammonia.
Iron forms a characteristic complex with thiocyanate which gives a deep red colored solution.
Aluminum forms a hydroxide complex ion in strong base and is precipitated as the insoluble hydroxide in weak base. Sodium, potassium and ammonium ions do not readily form insoluble salts so they can not be identified by precipitation. Sodium and potassium give visible emission flame tests and can be identified that way. The ammonium ion is a weak acid and will be characterized based on its acid-base properties. The barium and calcium ions can be separated and identified by the formation of insoluble compounds.