Dissolve 5.0 g of [Co(NH3)4CO3]NO3 in 50 ml of water and add concentrated HCl (5 to 10 ml) until all of the CO2 is expelled. Neutralize with concentrated ammonium hydroxide and then add about 5 ml excess. Heat for 20 minutes, avoiding boiling; [Co(NH3)5(OH2)]3+ is formed. Cool the solution slightly and add 75 ml concentrated HCl. Reheat for 20 to 30 minutes and observe the change in color. Purple-red crystals of the product separate on cooling to room temperature.
Wash the compound several times, by decantation, with small amounts of ice-cold distilled water; then filter under a water aspirator vacuum with a glass fritted funnel (medium porosity). Wash with several mililiters of ethanol. Drying in an oven at 120oC to remove solvent yields [Co(NH3)5Cl]Cl2. Calculate the yield.
Experiment from Synthesis and Technique in Inorganic Chemistry, Angelici, R.; J. W. B. Sanders Company: Philadelphia, 1969.
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