Assay cyanide solution by "Lead Boat"

[fireguy]

When trying to analyze a solution by fire assay, there are several options. One technique is to use a "lead boat". Starting with lead foil, fold into a rectangular tray. Be sure to fold the corners so they wont leak.

Add an accurate amount of solution (by pipetting, graduated cylinder, weight, etc).

Place on hot plate. Do not boil. Don't melt the lead. Wait for solution to completely evaporate. Add inquart if needed. Fold into a compact cube and cupel.

The size and shape of the lead boat can be decided by the volume requirements:

 

[Auassayer]

Fireguy,

I have used a much simpler and more reliable method than the evaporation method you cite, or the Chiddey, or Copper Sulfate extraction or litharge absorption etc.. I started using this 20 years ago after I swore earlier in my career I would use a different method. the method is simple as follows;


Weigh up about 300 mls of the cyanide solution and place in a 1000 cc griffen beaker, and place under a fume hood. Add about 20 mls of hydrochloric acid. (make sure this is done under the hood). Add about 10 grams of test lead (prescreened to get rid of dust). Put on hot plate, cover with a watch glass and bring to a boil. Boil for one hour, remove from hot plate and allow to cool a bit. Decant and dispose of the acid solution properly. Rinse the test lead in the beaker with DI water a couple of times and ten dry on the hot plate, be careful not to melt the lead. When dry, transfer the test lead to a lead boat made out of a 3" x 3" piece of 0.006" lead foil. Add a silver inquart, wrap up and cupel. Complete as normal...opt Au = (29.167/solution weight) x mg Au recovered.

This is a very very easy procedure and has never failed for me.

 

[Jdd]

I have a very easy fire assay of solution. Using AA get a estimate of the gold in oz/gal. Using 30g fusion pots put two sandwich bags in the pot. Put in about 9 or 10 medium sized cotton balls and fuse. The cotton balls act as a reducing agent and absorb the solution that your testing. Treat now as a normal fire assay.

 

[fireguy]

I have a very easy fire assay of solution. Using AA get a estimate of the gold in oz/gal. Using 30g fusion pots put two sandwich bags in the pot. Put in about 9 or 10 medium sized cotton balls and fuse. The cotton balls act as a reducing agent and absorb the solution that your testing. Treat now as a normal fire assay.

Interesting idea JDD. Wouldn't you need to dry first to remove the moisture? I have done a similar test by adding the flux to the crucible (use a crucible glazed with borax to make it less porous), and pipetting the solution into a depression in the flux. Dry and fire.

Probably need to add an inquart for most samples unless very high grade solutions.

 

[Jdd]

There is no need to dry unless you are using more than a 30ml sample. The cotton balls absorb all the solution. We usually put the fusion pot on a hot plate to dry. Samples can be analyzed by %\wgt or pipetted with known amount.

 

[devan]

I use the same method, except I pipette the solution directly into the Pb flux, using the plastic sandwich baggies to line the 30g. crucible. I add about 15 grams of pure test lead, and the Cyanide aids in the reduction process. No need to dry if the sample size is under 30 ml, but it doesn't hurt either if you do dry it (if time is not a factor)

 

[Hutzler]

That's pretty interesting, Devan.