Nikel interference on fire assaying

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david1205

New Member
#1
I would like to consult one problem regarding the Nickel intereference on fire assaying. The bead forming will be a big issue as the Nickel concentration is high. How could I modify this? Thanks.
 
fireguy

fireguy

Supermoderator
#2
david1205 said:
I would like to consult one problem regarding the Nickel intereference on fire assaying. The bead forming will be a big issue as the Nickel concentration is high. How could I modify this? Thanks.
Hi David:
You may be able to use nitric acid to dissolve some or all of the nickel. This will also dissolve the silver, so this assay will not be good for silver only gold. The acid will also dissolve other things, reducing the weight of the sample. You will need to start with a know weight, for instance 15 grams, dissolve with nitric acid (I would try 50%, heated gently), filter, wash, re-pulverizer and weigh. The assay calculations should be based on the starting weight and not the final weight. Is this a sulfide material? If so you may want to start with a roast first to drive off the sulfur.
 
R

rookieminer

New Member
#3
When using nitric acid as a pretreatment for a fire assay on a sulfide ore, is it necessary to roast the sample to drive off the sulfur first?

rookieminer
 
fireguy

fireguy

Supermoderator
#4
rookieminer said:
When using nitric acid as a pretreatment for a fire assay on a sulfide ore, is it necessary to roast the sample to drive off the sulfur first?

rookieminer
I would suggest only doing the roast. This will remove the the sulfur and will make the assay much cleaner. Unless you have very high concentrations of base metals (copper, nickle, etc) you should not have a problem. Some of the base metals will report to the slag, and some will collect with the lead and be absorbed into the cupel.

If you have very high base metal concentrations you can reduce sample size, or add extra reducer to drop a larger lead button and use a larger cupel- or both.
 
D

david1205

New Member
#5
I would suggest only doing the roast. This will remove the the sulfur and will make the assay much cleaner. Unless you have very high concentrations of base metals (copper, nickle, etc) you should not have a problem. Some of the base metals will report to the slag, and some will collect with the lead and be absorbed into the cupel.

If you have very high base metal concentrations you can reduce sample size, or add extra reducer to drop a larger lead button and use a larger cupel- or both.
Hi, we got a problem on fire assaying regarding the silver result which is generally high compared to real result. our materials normally are sludge which it comes from the wastewater. It will contain higher copper or nickel metal. Our fire assaying used the Pb/Ag method to collect Au, Ag and PGMS. And then doing the parting and them aqua-regia digestion, and followed by ICP analysis. We will record the weight of the final bead. And then analyze the Au, Pt and Pd by ICP directly., However, the silver result was calculated by subtracting the Au, Pt, Pd and other residue. But it seems that the silver result is generally high and not reproducible. Is there any way we could improve the silver result? Thanks.
 
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