G’day; Once again into the breach dear friends! Metabisulphite has
no place in a jeweller’s workshop. The trouble is that the pickle
called ‘Sparex’ is NOT meta bisulphite but sodium bisulphAte. Also
sold as pool pH adjuster, Bisulphate is stable; bisulphIte is NOT
stable. That’s why it gives off choking sulphur fumes. However,
Bisulphite has a place - in disinfecting beer bottles before reuse.
Home Brewers use it for that purpose. – Cheers for now,
John Burgess; @John_Burgess2 of Mapua Nelson NZ