Poor mans nitric vs lab grade nitric

[denim]

I have read in various places on this forum that poor mans nitric can cause problems especially with regards to silver refining. I understand that some put their nitric in the freezer to drop out the salts (chlorides). Is this really necessary if I am only dealing with gold from fingers, fiber cpu's, and other plated metallic parts. I use poor mans nitric due to the ease of availability of battery electrolyte and the fact that sodium nitrate ships without a hazardous material surcharge. Thanks in advance.

 

[gold4mike]

I use poorman's nitric on pins by first adding the sulphuric and an equal amount of water, warming the solution on a hotplate, then adding sodium nitrate a couple of teaspoons at a time until I no longer get a reaction.

Decant immediately to avoid the growth of copper sulphate (?) crystals in the beaker. I add another roughly equal volume of water to avoid the crystal growth and filter through coffee filters to catch any gold foils that have already loosened from the pins.

I realize there are better methods for dealing with pins but, doing toll refining for others, its tough to meet promised completion dates and keep batches separate when using acid peroxide or a deplating cell.

The main problem I see using poorman's nitric in this manner is managing the growth of the crystals and the large volume of solution I create by trying to avoid them.

 

[butcher]

Poor mans nitric acid would be ok for gold, the sulfate salts will not be a problem with gold, but if your nitrate salt was high in chlorides it could dissolve your gold when you do not want it to, the chlorides can be removed easily from your nitric acid see below.

With poor mans nitric acid the problem of using it with silver is not the small amount of chlorides the nitrate salt may have contained, as these can be removed easily.
The chloride ions can be removed from the nitric acid, by using silver nitrate solution, forming a precipitant of silver chloride; decanting the silver chloride would leave nitric acid chloride free.

When you make poor mans nitric acid using a nitrate salt and sulfuric acid, you make nitric acid mixed with a sodium or potassium sulfate salt, it is the Na2SO4, or K2SO4 that you try to precipitate out of solution, although chilling the solution you can remove more of these salts, you cannot remove them all without distilling your home made nitric acid, it is the sulfate salts that become a problem with your nitric when working with silver, this will form silver sulfate which is not very soluble, and the silver sulfate is harder to recover silver later (melting with iron).

You can use your homemade nitric acid for silver if you distill the nitric acid, for a more pure nitric, leaving the sulfate salt behind in the reaction vessel, the chlorides carried over in the distillation is cleaned up from the nitric with silver nitrate solution, as stated above, this way you can end up with a nitric acid solution free of sulfates or chlorides, which will make it easier to use on silver, or for parting your in-quartered gold where you wish to recover the silver.

 

[denim]

Thanks for the responses gentlemen- much appreciated.