Volhard Titration waste treatment
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I would just accumulate it, filter it, and incinerate it with the rest of the sweeps.
Adding zinc or other reductant makes a nasty H2S smell. I suppose you could oxidize the SCN away with strong bleach, and just have silver chloride...
Adding zinc or other reductant makes a nasty H2S smell. I suppose you could oxidize the SCN away with strong bleach, and just have silver chloride...
If the titration were done right, there would be no silver remaining in the solution. It's all precipitated as silver thiocyanate, AgSCN. I would filter out and rinse the AgSCN. The solution now contains mainly copper, some iron from the indicator, and nitrate.
The solution can then be treated as any other acid waste, using methods well covered on this forum.
Since I've never worked with recovering the silver from AgSCN, I'm not sure how I would attack the problem. You may be able to use the Karo syrup/sodium hydroxide method as with silver chloride. Melting with sodium carbonate might work. In an old Google book, they converted the AgSCN to AgCl by boiling the salt in a little conc. HCl and then adding nitric drop by drop until the red color first disappears. At that point, it is supposedly converted to AgCl, which can be converted to silver using one of several methods well covered on the forum. I prefer the Karo/sodium hydroxide method.
In any case, I would certainly use a fume hood, in case any cyanide products are emitted.
Maybe 4metals can chime in here. He has mentioned the use of thiocyanate with silver.
The solution can then be treated as any other acid waste, using methods well covered on this forum.
Since I've never worked with recovering the silver from AgSCN, I'm not sure how I would attack the problem. You may be able to use the Karo syrup/sodium hydroxide method as with silver chloride. Melting with sodium carbonate might work. In an old Google book, they converted the AgSCN to AgCl by boiling the salt in a little conc. HCl and then adding nitric drop by drop until the red color first disappears. At that point, it is supposedly converted to AgCl, which can be converted to silver using one of several methods well covered on the forum. I prefer the Karo/sodium hydroxide method.
In any case, I would certainly use a fume hood, in case any cyanide products are emitted.
Maybe 4metals can chime in here. He has mentioned the use of thiocyanate with silver.
Thanks for the replies.
"I would filter out and rinse the AgSCN. The solution now contains mainly copper, some iron from the indicator, and nitrate.
The solution can then be treated as any other acid waste, using methods well covered on this forum."
That is how I have been treating it after I accumulate a few gallons.
Best Regards, Martin
"I would filter out and rinse the AgSCN. The solution now contains mainly copper, some iron from the indicator, and nitrate.
The solution can then be treated as any other acid waste, using methods well covered on this forum."
That is how I have been treating it after I accumulate a few gallons.
Best Regards, Martin
The silver thiocyanate can be rinsed well as it is all but insoluble in water, I havent looked this up lately but if I remember correctly the solubility in hot water is something like 0.000 something grams per 100 CC. And much less soluble in cold water. So rinse it well.
It also decomposes with heat so melting it under a borax / soda ash cap will give you a button. I usually titrate an operating silver cell with a 1 milliliter aliquot so that means each titration has somewhere around .06 grams per titration if your cell is running at 60 g/L. So even if you're titrating 3 times a day, 5 days a week, you still don't generate a gram of silver.
Filter it out, treat the waste, and do what Lou says, save it with the burnables.
It also decomposes with heat so melting it under a borax / soda ash cap will give you a button. I usually titrate an operating silver cell with a 1 milliliter aliquot so that means each titration has somewhere around .06 grams per titration if your cell is running at 60 g/L. So even if you're titrating 3 times a day, 5 days a week, you still don't generate a gram of silver.
Filter it out, treat the waste, and do what Lou says, save it with the burnables.
