@Rudeofus: You were right! An hour or two after I developed film in tap-water, keeping the used developer in a bottle, I noticed some cloudiness formed which became a finely powdered precipitate. I'm doing more experiments to see how long before the precipitate starts forming. If it's at least 30 minutes, it's probably not a problem. Otherwise, I have a problem. I'm also doing an experiment with metaborate in tap-water to see what happens.
And thanks for answering Relayer's question about 4-mol versus 8-mol. Those names are confusing.
@Relayer: If your developer using borax+carbonate had a pH of 8.3, then I think it should act the same as my developer. The digitaltruth times are starting points, and if it's "slightly dense", then the time was close. I suggest trying 7.5 minutes at 21C. Note that carbonate will not dissolve in propylene glycol.
@PeterB: I think you're correct in that the reaction is 1st-order. But *both* reactants are declining in concentration, which I think results in a 2nd-order reaction and thus a different half-life. I'm a computer scientist, not a chemist, so I'll need to take some time to go through those equations.
Last edited by albada; 07-22-2012 at 05:01 PM. Click to view previous post history.