Homebrew PCBs

Roger Blair wrote:
>  
> 
> I wish to prepare some HCl/H2O2 etchant, and I have 10% HCl. (10% HCl is 
> $5 per gallon, but 40% HCl which is what I need is a lot
> more expensive)
> 

You would end up less than you started with as others have commented. 
30~35% (wt) HCl is readily available as brick cleaner/ pool acidfier 
here in Australia. Even sold in 250ml bottles up to 20L drum at some 
local hardware stores. Its possible to remove some of the water, but not 
practical. Normally, dry HCl is produced in an oven and then dissolved 
in water until saturation, of which you get about 35% acid at STP.

Adam