metabisulfite and sodium bisulfite

[arthur kierski]

sometimes when i add smb to an ar solution to precipitate gold,it does not precipitate-----to this solution i add an equal quantity of sodium bisulfite and the solution becames brown and the gold precipitates----
could someone tells me what happens?

 

[jimdoc]

As far as I know they should both work the same,maybe your SMB
went bad for some reason.

Jim

 

[lazersteve]

Arthur,

It could be that you have excess nitric in the solution that is preventing the first addition of SMB from precipitating the gold. Try adding the sodium sulfite first, then the SMB, and see if you get the same results. If you do it may be that you need to de-noxx your solutions better before adding SMB and/or sodium sulfite.

SMB requires some water to react. If your solution is very concentrated you may not be generating enough SO2 gas to precipitate the gold. Try adding a little water to get the SMB reacting. A little free HCl is also a good thing when using SMB.

Could also be that your SMB is bad, if the SMB is clumped up it may have lost some of it's reducing power due to exposure to water in the air. Keep your SMB in a sealed container away from moisture. Your SMB should flow freely like table salt.

Steve

 

[arthur kierski]

thanks jim and steve for the replyes----yes , my smb is stony(clamped ) by moisture or air----it probably went bad----

what is the diference in using sodium sulfite or sodium bisulfite or sodium metabisulfite?or there is no diference?
ps.i know that bisulfite and metabisulfite have hydrogen in its formula ,making it acid----while sulfite is alkaline