Question about dropping gold

[plamenppp]

Last night a strange thing happened. I used AR to extract some gold from cpus and ram memories. I carefully collected all the liquid at a 5 liter plastic dish. I left it there for a couple of hours and started dropping the gold liter by liter. For my surprise alomost nothing dropped. I used urea, water and SMB. 30 minutes ago I tried to drop the last 1 liter liquid. At for all my astonishment the gold dropped immediately - nice brown collor and lots of mud.

Is it possible the dissolved gold to fall at the lower parts of the 5 liter dish and this to cause this strange accident?
I've had problems with dropping the gold of all kinds - not enough SMB, not enough urea, not enough waiting but this was more than strange.

 

[butcher]

I believe the gold would be in all parts of the solution, using urea might have had something to do with your reaction (gas rising in solution)???
Or reaction of urea de-NOx-ing the solution was not complete on the first portions you tried precipitating (so you still have them right), (they may still contain gold), just because it did not precipitate does not mean it was not there???

Did you use stannous chloride to test solution? Remember nitric in solution will not let gold precipitate, or will not let the stannous chloride form purple of cassius reaction, if I tested negative with stannous and suspected nitric, I would take a small sample few drops of solution in test tube and evaporate (hair dryer or candle will work with test tube) or some other method, then add water and re-test with stannous chloride on Qtip.

With aqua regia, the removing the unused nitric in solution (and being free of base metals in solution) is very important,

I would not use urea, I tried it several times when i first started learning, I did not like the trouble I had with it, evaporation method may take a little more time but it works well for me and adding (Harold’s trick gold button insures nitric is gone).

Also limiting the nitric used (in aqua regia reaction to dissolve gold adding it a little at time (as the trick GSP taught us), instead of mixing it up with HCl at the beginning, these tricks of the trade have made using aqua regia much easier for me

 

[plamenppp]

I dropped the gold with the help of some heat. I added the trouble solution to the last batch of dropped gold and waited. At the end there was a nice brown mud everywhere and it took a lot of time to melt it with gas torch (no 02). The result is 10 gr gold