Tetrammine cupric sulfate

F. Mazzi. Acta Cryst. 8, 137-41 (1955). x-ray crystal structure of cupric tetrammine sulfate monohydrate. 

Salts of this complex ion can be crystallized from ammonia solution. The best known one is cupric tetrammine sulfate monohydrate, Cu(NH3)4S04-HoO, which has the same deep blue color as the solution. 

What is the difference in constitution between tetrammine cupric sulfate and cupric ammonium sulfate ... 

A dissolved substance can also be made to crystallize by adding a liquid which will mix with water but which is a poor solvent for the substance to be crystallized. Thus tetrammine cupric sulfate is precipitated from solution in Experiment 5 by adding alcohol. Evaporation could not be used to crystallize this salt, since ammonia would be lost on boiling and the salt would decompose. Another instance of the addition of a second solvent to bring about crystallization is in Experiment 26, in which chromium trioxide is made to crystaUize by adding excess of sulfuric acid. Here the desired product is so very soluble in water that it could not be crystallized in pure form by evaporation. 

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