Sodium sulfite vs. Sodium metabisulfite

[huggybear]

Hi All,

Forgive me, I'm sure this topic has been discussed in depth before. But as a new member, I found it hard to pinpoint a thread that compares the two in detail.

Is there a distinct advantage (be it more effective or safer) using Sodium sulfite vs. Sodium metabisulfite to drop out gold?

Thanks,

huggybear

 

[Lino1406]

No difference except SMB contains more SO2 units for unit weight

 

[huggybear]

Thanks Lino.

 

[orvi]

I found them practically identical in terms of efficiency and performance. But as Lino wisely pointed out - you need two equivalents of acid such as HCL to liberate active SO2 from Na2SO3. So the consumption of the acid is higher with sodium sulfite. It can cause minor problems regarding the solubility of silver chloride in heavy chloride solutions - hence adding Na2SO3 = relatively basic compound will eat up twice as much free acid in solution, thus basifying it more = likely more drag-down of silver chloride or other base metals along with gold.

I used sodium sulfite for quite a long time, as it was accessible in large quantity for bargain price. Altough I am slowly diversifying my precipitant portfolio and use metabisulfite more often, when I am concerned more about purity