I am at the end of my straw here.
I tried to precipiate basic copper carbonate from a solution of copper II chloride through the addition of a saturated solution of sodium carbonate. Both solutions were at around room temperature. The copper chloride was dissolved in just about enough distilled water.
At first, I slowly added the sodium carbonate solution to the solution of copper chloride, but after the short burst of bubbling subsided, I dumped the rest in, which resulted in the precipitation of a solid copper compound.
I knew right away that something was off: The basic copper carbonate I previously made was the expected green-blue color that leaned more towards green. I believe I made that batch using copper II acetate instead of the chloride I used this time. The precipitate that formed was clearly more towards the blue end of the spectrum and had a harder time settling to the bottom after stirring was stopped, which told me that something went wrong.
I took a sample of the solution with some re-suspended precipitate and heated it, closely monitoring the temperature. At around 70°C, the solution turned pitch black.
After stirring was stopped, a deep blue solution and a black precipitate at the bottom remained.
Basic copper carbonate shouldn't decompose at these temperatures if I am not mistaken, which is why I tried heating the solution. To the best of my knowledge, I just made copper hydroxide instead of the compound of my interest.
Can someone tell me what I did wrong and how this could even happen? I read somewhere that is was fairly tricky to produce copper hydroxide, but for me, the opposite is true. Any advise highly appreciated, I am going nuts!