----- Original Message ----- From: Philip Pemberton To: Sent: Saturday, September 11, 2004 12:26 AM Subject: Re: [EE]: Ferric chloride etchant disposal > In message <9B73ACC8-0379-11D9-AADA-000A95E5DF26@mac.com> > William "Chops" Westfield wrote: > > > Lye is seriously DANGEROUS stuff. > > And yet it's used as a PCB developer in some cases... Hm. > > > Adding the copper from a couple square feet of boards (at about 1oz/sw > > foot) isn't a big deal. > > Well, there's an outside drain that the guttering runs into. I suppose the > old "chuck it in a bucket, heavily dilute and dump down the drain" trick > might work... ISTR Radioshack actually printed that on the side of the > bottles of etchant they sold, but I wouldn't take their word for anything. > > The other suggestion I got was to chuck the FeCl into an ice-cream tub, add > some Plaster of Paris, then cover the tub, put it in a bag and leave it to > set. I suspect PoP is alkaline, so it would theoretically neutralise the > FeCl+HCl, %DEITY knows what byproducts it would produce though (probably > CO2). No, plaster of paris is partially dehydrated calcium sulphate which is very insoluble in water. Adding water to it rehydrates it but does not desolve it. The heat this produces is due to the rehydration and not a chemical reaction. Adding the FeCl to plater of paris would result in a brick which locks up the FeCl. It would probably leatch out with time if placed in running water but it should be safe to dispose of in a normal landfill site. If you do have any HCl in your etchant, you can easily nutralise it with sodium carbonate or bicarbonate - cheap and very easy to get. You will get bubbles forming until all the HCl is nutralised. When it stops bubbling you're done. This obviates the need for indicator paper. Regards Sergio Masci http://www.xcprod.com/titan/XCSB - optimising PIC compiler _______________________________________________ http://www.piclist.com View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist