Dale J. Chatham wrote:
>
>
> My guess is that you have CuCl as the blue sludge. I suppose it could
> be CuOH, but you'd have to convince yourself that Cu would rather bond
> with OH. A smell of chlorine when you are reacting would be a clue, or
> bubbles and a yellow gas.
>
CuCl is copper(I) chloride, a white insoluble and unstable solid.
Or you have to convince yourself that sodium ion prefers chloride,
therefore leaving copper ion nothing else but to except the hydroxide.
If the solid is a bright pale blue with clear liquid then you can be
sure its copper hydroxide.