Homebrew PCBs

Stefan Trethan wrote:
>>One option is to etch in a small tray and then immediately dispose of the 
>>used etchant it into a 20L drum (correctly labeled) and worry about it 
>>another day when it drum is full.
>>
> 
> 
> 
> ;-)))
> 
> What happens if you neutralize the stuff, then let it dry out it an open 
> tray?
> What's left there? copper, in which form? and what is the result of dried 
> out neutralized etchant?
> what results from neutralizing acids at all? how is this ph neutral mixture 
> called?
> 


All the common etchants (persulfates, ferric chloride, 
cupric chloride, HCl+H202) that finished etching copper will 
precipitate copper(II) hydroxide (bright blue solid) when 
neutralized. The copper(II) ion is only soluble when the 
solution is acidic (pH < 7) as it is with all the above 
etchants. The dried solids will contain mixed salts and 
copper(II) hydroxide, and maybe some copper(II) oxide. It 
depends on the etchant. Which etchant were you interested in ?


see;
http://lrs.ed.uiuc.edu/students/erlinger/water/background/ph.html



Adam