NedL
Subscriber
"To discard ammoniacal silver solution safely, a sufficient volume of either a 20% solution of sodium chloride or a diluted solution of hydrochloric acid is added to convert the silver compounds to silver chloride, which is insoluble and immediately precipitates. An excess should be added to ensure complete precipitation of all the silver diaminohydroxide. This makes the solution non explosive."
Excellent! I'll read that carefully. I do this with left over silver nitrate containing waste: first salt to form silver chloride, which filters out easily ( and also sinks to the bottom of the container, so you can decant through a filter ), then somewhat later after that step I put in a small amount of polysulfide just to be sure any remaining silver is in an insoluble form.
Regarding ammonium chloride, if you make a very strong solution ( approaching saturation ) it will dissolve silver chloride fairly well. Not very economical, but a good trick to know if you are having any trouble with salt prints... wash wash wash them and then put them into a very strong ammonium chloride solution, prior to fixing in thiosulfate. If the combination of paper and process you are using is troublesome to clear perfectly, this can be very useful. I'm not sure how this relates to the chart Rudeofus posted above.
Also I did not know that silver citrate is soluble in sodium sulfite. That is very interesting -- and also would explain some things I've wondered about. The H2O2 bleach many of us played with converts silver to silver citrate, and I think the process can be sped up by adding sodium citrate ( I know for sure you can rehalogenate with chloride or bromide by adding sodium chloride or potassium bromide, I ran a series of tests and thought it might be useful to convert some papers to warmer tone or maybe even make them more lith develop-able. ) So now I'm also wondering if pot ferri with sodium citrate will work like pot ferri with sodium chloride or bromide? If that worked, and we could use sodium sulfite to remove the silver citrate, it might be an efficient way to do reversal.
This is an interesting thread.... thanks to everyone participating
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