Using urea to dispel nitric

[Dr. Poe]

I use a crock pot to heat my gold chloride solutions to 160F (72C) prior to using urea. The problem is that the escaping gases cool the solution too much for additional urea to work. I then must wait for the temperature to rise before testing or adding more urea. If I don't wait and raise the temperature, I get a false negative for the presence of nitric acid in solution.
It's best to add only enough nitric acid to keep the reaction going when using aqua regia. So if you have had problems with the reduction of your gold to the metallic, this might be the reason for it. Dr. Poe 8)

 

[glondor]

Thanks Dr Poe. I have wondered why urea sometimes has no effect when I know there is nitric in the mix. When doing cpu's i find i need extra amounts of A\R just to overcome the dilution factor. ( it may take a gallon of water to cover 5 pounds of chips in a bucket) After a thorough rinse there may be 2 gallons of dilute aucl with excess nitric in the solution. Evaporation in these cases is not an option as it would take over a day. So I need an effective way to kill excess nitric. I will try heat.

 

[samuel-a]

Evaporation in these cases is not an option as it would take over a day. So I need an effective way to kill excess nitric. I will try heat.

glondor

Wouldn't it be just simpler if you heat your AR while dissolving the metals?
That way, even upon dilution, the AR will be very aggresive and no exess nitric will be used...


You can do several pounds easily in 4000ml borosilicate beaker.

 

[glondor]

Hi Sam. For smaller batches I do use heat. My largest standard beakers are 2 liter. When I use a pail I try to heat in a hot water bath. I have a 5 liter beaker but I think the ceramics may be a little hard on it. I have had 4 two liter beakers break in the last 3 months for no apparent reason. Lucky they were all empty at the time. I need better beakers.

 

[butcher]

I like the corning ware type dish on the hot plate for heating solutions, also the amber or purple corning vision type stove top dishes work great too.