Not to thread-jack, but what is the proper method of disposal of the
CuOH precipitate following this procedure?
--- In Homebrew_PCBs@yahoogroups.com, YD <yd_br@...> wrote:
>
> Your method is what works for me, except I use the
> solution itself as an indicator.
>
> First off, mix 40 g NaOH to 1 liter of water to make a
> 1 molar standard solution (even 4 g in 100 ml will
> last you a lifetime).
>
> Place 10 drops of CuCl2 in a test tube or other
> similar container. Add some water to increase the
> volume a bit, quantity isn't critical but don't make
> it too transparent. Double or triple is fine.
>
> Fill the dropper with the standard solution (wash it
> off first). Add it to the test tube one drop at a
> time. A darkish cloud forms where it hits. Shake the
> tube to dissolve it. As you keep dropping it will
> start forming tiny white flakes. Keep shaking it. Stop
> when the flakes refuse to dissolve. Divide by 10 (or
> however many drops of CuCl2 you used) to find the
> molarity.
>
> The NaOH at first reacts with the HCl forming NaCl
> and H2O. The initial darkish cloud is due to a
> momentary formation of CuCl which reacts with the
> remaining HCl back to CuCl2. When the HCl is exhausted
> the reaction forms CuOH which is only weakly soluble
> making it cloudy.
>
> As for density you can weigh 100 ml in a tared
> container and multiply by 10.
>
> You can also use a tared container of unspecified
> volume by first weighing the solution and then the
> same volume of plain water. Divide the former by the
> latter to find the density directly.
>
> The methods above are ballpark only, but should be
> within 10% tolerance. CuCl2 itself is pretty tolerant
> about variations as long as they stay within limits.
>
> - YD.
>