i placed a bottle of used ferric chloride somewhere in a cabinet and after about 2 weeks, i noticed that there is a sludge-like matter below. do i have to remove that by filtration, or just let it stay with the mixture?
I alwas leave it there.
If you add a Small Amount of Hydrochloric Acid to the Ferric Chloride, you probably will not get this to precipitate to happen.
Ferric chloride precipitates out a solid (iron? copper chloride?) as it etches. If you do an inverted etch rather than agitating, it falls right off the panel to the bottom.
As it is a solid waste product, it might be slightly better to filter it out, but I think it's inert at this point so it shouldn't matter one way or another.
I alwas leave it there.
If you add a Small Amount of Hydrochloric Acid to the Ferric Chloride, you probably will not get this to precipitate to happen.