Irons2 said:
Very nice. There's more than one way to get the job done, it seems.
Thanks Irons2.
Yes, doing this the first few times as per Hoke, i've thought that there must be a more convenient way and tried to alter the process several times. I found this way to be to must efficiant (time and labor wise) with same results.
ericrm said:
my only question, is what do you do with the waste that has oxalic acid in it?? do you neutralise it just like regular chloride/nitric waste or is it something different?
ericrm said:
samuel at 3:33 is your beaker at tall form 2000ml?
The majority of the oxalic/oxalate actualy decompose during the process, however if you use excess of it, some will be left in the solution.
After making sure pH is back at 0, I'm adding it to my regular acid waste buckets. (btw, if it is clean enough which usually it is, i keep it and use it as dilute HCl to wash very dirty gold from other process).
Though not Toxic, i wouldn't recommand handling oxalic acid solution without gloves. Chronic exposure to Oxalic acid (ingestion and/or skin absorption) is a known couse for kidney stones.
The flask in 3:33 is not a tall form, just seems that way... i think it is the angle of camera that make it look like that.
bswartzwelder said:
If the gold you dissolved with AR had any other metals present, would they also precipitate out with the oxalic acid and sodium hydroxide?
Ideally no, but we know there's never 100% refining.
Oxalic excels in seperating Copper and Palladium from gold, less so for Silver (chloride). But for the last, we used dilution and smb in the first refining.
Of course, if pH goes over 1-2 some insoluble oxides/hydroxides of some base metals (if there are any) may form.
That's why the addition of base is done very carefully and the later HCl washes are very important and should not be skipped.
