Great video ! Keep it up. Question: Does the HCL remove all the sulfides (same as roasting), or should you roast the sample prior to adding chemicals ?
It is my understanding that the sulphur will produce hydrogen sulfide gas and chlorine gas as the sulfur takes hydrogen from the HCl. It also contaminates the solution with whatever the sulfur was originally bonded with. If you have a lot of sulfides, roasting in advanced would be a good idea.
Great video! I did also the aqua regia mix with the crushed rocks. I used HCL & Nitric acid, but I'm noticing when I use urea to kill the Nitric; the urea is not dissolving 100%. Half still floating at the top. Not sure to heat the mix with the urea in it?? Any suggestions?
I now dissolve the urea with water before adding it to the AR. This way you don’t get undissolved urea in the mix. You can also heat the AR to help dissolve the urea but you need to cool it down before precipitating.
Shouldn’t the solution containing base metals dissolved from the muriatic acid be rinsed out before using aqua regia to put any gold in solution in what’s left? Thanks!
Thanks for the demo. I once did this experiment. I added stanous chloride the aqua rigia rich mixture , the change of colour immediately happened. When I took the same sample for an XRF assessment, I was told there was no gold. How can this be Sir?
If the nitric acid is not completely neutralized, the stanous test will give you a false positive. Also if there is palladium in the test sample it could look like a strong positive for gold. Other metals can also contaminate the AR and give odd results.
I did the same experiment on a sample. The result was strange. The color of the sample changes to black gradually and takes about half an hour. Does this mean there is gold in the sample?
It probably indicates that you have other metals or PMGs in solution. Platinum, palladium or iron and copper. I have had this happen as well. Sometimes you just can’t get around it without doing more processing.
can't you just cut filter paper into strips, dip the strips in the solution and drop the stanous chloride to the strip. Much less waste than either procedure you chose
Yes, at times I do use them. When refining gold at higher concentrations the change on the paper strip is instantly noticeable, but the paper strip method is difficult for me to read with low gold concentrations. In the spot plate method, any positive test is not discarded. I save all the little squirts of positive tests, than once I accumulate enough I redissolve in AR and precipitate with SMB or ferrous sulfate.
@@thisoldminewithlars5324 I mean when you mix all solution in one beaker and then at 15:40 I little bit confuse, cause you didn't do the denox with urea, but use smb to get precipitate,,, is it we can get the gold without denox the aqua regia with urea?
I don’t use an excess of nitric in the tests so the denoting is minimal. I usually re-treat the ore after I do a test to get all the gold. Denoxing is critical if you have a lot of nitric left over. Other than denoxing, you will need to use extra SMB to precipitate.
