h0lx Posted April 21, 2007 Share Posted April 21, 2007 I was trying to make CuO and dissolved some CuSO4.5H2O in water and adding NaOH until neutral. along with the Cu(OH)2 some strange fine cyan ppt. formed. This shit isn't very soluble in water(didn't go away after diluting ~5 times) and doesen't go away with bouling either. What is it? how to get rid of it? Link to comment Share on other sites More sharing options...
styropyro Posted April 21, 2007 Share Posted April 21, 2007 I have had the same thing happen to me when I was making Copper Sulfate crystals. Just dissolving the Copper Sulfate in the water made the precipitate. I think its also Copper hydroxide, I've never needed to get rid of it, but I think that adding vinegar or some other acid works, someone correct me if I'm wrong. Link to comment Share on other sites More sharing options...
Rogue Chemist Posted April 21, 2007 Share Posted April 21, 2007 However low grades of CuSO4 are made, there always seems to be some CuCO3(I think thats what it is at least) present. A couple drops of dilute H2SO4 usually clear it up instantly, than add the base. Link to comment Share on other sites More sharing options...
h0lx Posted April 22, 2007 Author Share Posted April 22, 2007 hmm... but that PPt has three times more volume than the CuO.. and when the CuSO4 was dissolved, none of the ppt was present. EDIT: the PPT was indeed basic, I made the whole lot back into CuSO4 with H2SO4. Link to comment Share on other sites More sharing options...
Mumbles Posted April 22, 2007 Share Posted April 22, 2007 How old was the NaOH? It will absorb CO2 from the air to form bicarbonate. Copper carbonate occupies much more volume than CuO. From the dry powders I have I'd say a pound of CuCO3 is probably 7x the volume of the CuO. Link to comment Share on other sites More sharing options...
h0lx Posted April 24, 2007 Author Share Posted April 24, 2007 the NaOH is indeed really old, so that must be the problem. Although, the NaOH has always been hermetically sealed. Ah well, I'll just have to reattempt, this time with drain cleaner. Link to comment Share on other sites More sharing options...
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