Non-Chemical Urea vs Baking Soda

[joubjonn]

Quick question,

i have never refined anything, i just learned of this a few days ago and plan on spending at leased a month reading, watching and learning. i have purchased a few books already and have started to stock pile material. my background is mechanical engineering, i did take some organic chem my senior year of college so i know a bit about a chem lab.

why use the urea to lower the pH? why not just use simple baking soda to get the pH around 3.5-4 where all the nitric would be neutralized? i would think urea to be a bit dirty

 

[butcher]

The point is to remove any un-reacted nitric acid remaining not to lower pH, In refining I would not use urea, baking soda or any thing else to lower pH.

Raising pH can be counter productive, you can form nitrates, and if you raised it as high as you are talking about precipitate unwanted metals back out of solution.

Urea can be dangerous, it can form ammonium compounds, it does not work that well, baking soda can form insoluble carbonates, use of either of these would be a big mistake in my opinion.

Study the forum, you will find better methods that work best, like the use of the bare amount of nitric needed to oxidize the gold, so that basically the nitric is consumed in the reaction, sulfamic acid which has side benefits, using gold to consume free nitric in solution, or the tried and proven method of the three evaporation process taught in Hoke's book.

Many times depending on your material it is not necessary to use aqua regia (or nitric acid), to put gold into solution, and these methods can be easier to deal with to get the gold back out of solution for those unfamiliar with aqua regia, aqua regia is not as easy to deal with as you may have read about, and where ever you have read about it so far it sounds like you have not learned anything but miss-information, spend some time learning from Hoke's book and the forum.

 

[joubjonn]

appreciate it! i just started reading Hoke's book today. very good so far.

one other quick question, i live in Texas and it's getting pretty cold these days, especially in a month or so when i finally feel i know enough to try this, is it better to wait until it's warmer outside?

 

[butcher]

I work year round, sometimes the weather even has benefits, snowing is a great time to make my nitric acid.