Does anyone know at what temperature the SO2 from using SMB starts to break down and dissipate once it has been dissolved into solution? When heating a solution of AR that has had SMB used in it, how hot does it need to be to get past the false positive test may be the answer, but I still haven't found that answer also.
SMB question.
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SO2 is quite soluble in water also at higher temperature (significant also in boiling water), so boiling the SMB drop cannot easily accomplish the thing. You will need to physically boil out some of the water to force SO2 out mixed up with steam escaping. Can be done fairly easily tho, if really needed. SO2 will have appreciable pressure in the gas phase created, so the ammount of steam to force it out of solution shouldn´t be that excessive. Simultaneously, you will nicely pack the gold drop 
Thing which can help quite a bit is reduce the pressure. I regularly de-gas solvents etc. by evacuating the vessel with solvent, which cause rapid de-gassing of the dissolved gasses - alongside with minor evaporation loss of the actual solvent.
What is the purpose of the de-sulfurizing of the solution ? Just for convenience purposes (no smell in wastebucket), or some other intentions ?
Because sulfites and sulfates are easily scrubbed by calcium reagents. Forming insoluble calcium salts. So if it is only inconvenience issue, neutralize the solution to create sulfite salts, treat the waste with slaked lime (or better calcium chloride) briefly, scavenging all sulfates and sulfites and insoluble calcium salts, which can be disposed easily as they are after decantation.
Thing which can help quite a bit is reduce the pressure. I regularly de-gas solvents etc. by evacuating the vessel with solvent, which cause rapid de-gassing of the dissolved gasses - alongside with minor evaporation loss of the actual solvent.
What is the purpose of the de-sulfurizing of the solution ? Just for convenience purposes (no smell in wastebucket), or some other intentions ?
Because sulfites and sulfates are easily scrubbed by calcium reagents. Forming insoluble calcium salts. So if it is only inconvenience issue, neutralize the solution to create sulfite salts, treat the waste with slaked lime (or better calcium chloride) briefly, scavenging all sulfates and sulfites and insoluble calcium salts, which can be disposed easily as they are after decantation.
Can it be done without boiling?
With a heavy dose of SMB, I am curious if the false positive is hiding a positive test for other PGM's, and how it affects very low amounts of PGM tests.
By reducing the pressure, do you mean place the solution in a vacuum? I can do that pretty easily.
With a heavy dose of SMB, I am curious if the false positive is hiding a positive test for other PGM's, and how it affects very low amounts of PGM tests.
By reducing the pressure, do you mean place the solution in a vacuum? I can do that pretty easily.
Yeah. Reducing pressure is putting the thing under vacuum
Be aware of "boil" over from gas bubbles emerging from the solution and quickly expanding due to vacuum. Gasses are easily de-sorbed from solutions by means of reducing pressure. I can imagine that one can take slightly warm solution, put it under vacuum and gradually reduce the pressure. De-sorption of gasses from water is usually endothermic - so the solution will cool considerably. But if you manage to heat it with some hot water bath or anything like that, it will be usable approach in my view. It would be best to maintain the temperature to attain equilibrium, when no more gas would be de-sorbed, and then slightly rise it, causing the solution to start evaporating. And in this moment, last bits of gas will be eliminated as water vapor will constantly strip the SO2 gas, equilibrating from the solution.Altough I do not precisely know, how quantitative it would be in realistic circumstances (considering mainly time of the applied vacuum suction), but I think much more efficient than just heating the solution.
Thanks orvi that gives me a lot of new direction possibilities to consider.
One more question. Would calcium carbonate work, and leave a precipitate at the bottom of the solution? Something that could be filtered out of the way maybe allowing for better removal of any pgm’s that remain. I have plenty of calcium carbonate on hand.
One more question. Would calcium carbonate work, and leave a precipitate at the bottom of the solution? Something that could be filtered out of the way maybe allowing for better removal of any pgm’s that remain. I have plenty of calcium carbonate on hand.
Hi
After denoxing the gold containing aqua regia I used SMB solution to precipitate the gold out of solution. Gold precipitate out but got some lines on beaker wall as in attached pic. It seems to be gold powder stick to wall in this pattern. Can any one guide what might be the reason for these lines? As I was expecting that all gold will precipitate out and settle down with time. What I am getting is some gold stick to wall of beaker as it is a loss. I used glass rod to mix the SMB solution in Aqua Regia.Does it might be the reason for these lines?
After denoxing the gold containing aqua regia I used SMB solution to precipitate the gold out of solution. Gold precipitate out but got some lines on beaker wall as in attached pic. It seems to be gold powder stick to wall in this pattern. Can any one guide what might be the reason for these lines? As I was expecting that all gold will precipitate out and settle down with time. What I am getting is some gold stick to wall of beaker as it is a loss. I used glass rod to mix the SMB solution in Aqua Regia.Does it might be the reason for these lines?
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Do you clean your glassware thoroughly after each usage? ;-)
Marcel is correct, the glass ware need to be completely clean.
Specially fats and other organic material will do that.
These glass wares never used in fats. Always used in acids and washed normaly. Is it possible that gold which were dissolved in aqua have some glue in it causing this?
No, if it has been dissolved and then precipitated it will not.
But the glassware needs to be without scratches even, invisible ones.
And you need to clean them with proper cleaning chemicals.
I don't know what is available in Hungary, but our American members seem to prefer something called Bon Ami, if I remember correctly.
Ohk. Thanks allot.
There it was, I just remembered one name from the discussion, and it was the wrong one
I did of course remember the wring name, sorry for bad advice.
Find out what the wine restaurants use to clean their glasses and you might find good alternatives.
cejohnsonsr1
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Alconox is what I used to use for cleaning. After you pour off the waste, try to rinse with distilled water and see if it settles. If so, probably dirty glass. If not, maybe scratches. Either way, Aqua Regia will dissolve it. Nothing lost. Yet.
Thanks for all replies. It easily settle with water.
