The reaction is (NH_4)_2 S_ 2 O_8 -> CuSO4 + (NH4)_2 SO. The resultant liquid is less harmful than ferric chloride but should still be treated with other chemical waste
== Photoresist etching with Sodium Persulfate ==
# Print inversed PCB on two layers of transparencies, and make sure that there is visible text to be able to identify the side later
# Place glossy side of transparency on the glass of the UV exposure box, and the matt side (with the toner) face up - you should be able to read the text inverted now
# Peel back the protective film from the pre-sensitised PCB, and carefully place it over the transparency
# Expose for ~3 minutes (time needs to be experimented with still), with a weight (such as one of the bottles) on the cover for pressure
## Whilst the PCB is getting exposed, pour 1cm worth of soda (french: soude) into a container
## Prepare another container with just water, to rinse of the soda
# Remove PCB from UV exposure box, and place into soda solution. Stir and agitate until the soda and PCB until there are no more violet traces that leave
# Remove PCB from soda solution, and rince off with water in other container - use plastic tweezers to handle it
# Attach PCB to support wire, and place the PCB into the Sodium Persulfate solution, and wait until you can see the resin (should take ~20 minutes)
## Whilst waiting, pour the soda back into its bottle, and rinse the containers
# After you can see the resin, remove the PCB before the traces get etched away, and rinse it off
# Pour Sodium Persulfate back into its container and clean up
(photos to come)
== Safety ==