Transition elements
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For my chemistry investigation I am comparing the growth and colours of various crystal compounds under different variables.
I have had difficulty in forming tetra-amminecopper(II) crystals. I have used a method provided by this site twice and each time the same result occurs. Once I form the solution, a green powder is left. I was wondering if you could tell me what the possible reasons for this could be? Also is there another method that I could attempt in order to obtain crystals of a tetra-amminecopper(II) salt?
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Ulex replies
You might care to try this version but I have to say that getting this complex salt to crystallise is a tricky and uncertain business (but you know that already!)
Dissolve 5 g of copper sulphate crystals in 20 cm3 of water and add, slowly with agitation, of 2M ammonia solution until the precipitate which first forms is completely re-dissolved. To this solution add 30 cm3 of ethanol and leave the mixture in a fridge or ice bath. Filter the crystals (if you get any!) at the pump.
Good luck! Whatever else happens, you shouldn’t get any green powder!
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updated: 01 April 2008
