Concentrate Nitric Acid ?

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Noxx

Well-known member
Joined
Feb 24, 2007
Messages
3,365
Location
Quebec, Canada
Hello,
Is there a way to concentrate my nitric acid without distillation ?
I made it with with Sulfuric acid and Potassium Nitrate. Final product is about 30% Nitric.
Thanks
 
Have you cooled the solution down to below zero degress C and filtered? This will help drop out as much salt as possible leaving you with more nitric acid in the solution. The only other way that I know is careful distillation.
skullnbones_smallrev.jpg


Steve
 
Yes, I cooled it unden 0°C.
Do you have good websites explaining how to distillate ?
I have most of the appartus needed, I just don't have the right tubing. I suppose I can't use vinyl tubes with rubber stoppers...
Thanks
 
I now think I know the reasons for your nitric acid questions on the gold testing thread. Do you plan on using your homemade nitric to test the gold you are buying? This could be a big mistake. Buying gold is an area you don't want to make mistakes in. Using this Mickey Mouse nitric puts another big variable into the mix. If you're just playing around or just have a pioneer spirit, that's one thing. When you put hard earned cash out for questionable gold, that's another thing. If you can't find good nitric, order some bottles of testing solutions from eBay or, better still, from a jeweler's supply company. They're only about $3 per bottle.
 
I taught I could use my own but then I realised I need good quality nitric. But no I won't use it for testing. I'm having hard time dissolving copper mixed with gold. My acid is too weak and doesn't dissolve it much...
Thanks
 
I bought 22K testing solution from ebay.. I kinda looks like AR (it just might be. The label says "contains HCL and Nitric Acid")

I've been testing everything for the sheer fun of it ... :lol:

I paid $5 with shipping for it, so I'd say def. buy the stuff instead of trying to make it.

The only reason I bought it was because I bought it at the same time as all the other chems for AR and I wanted to know when I got at least 22K out of my batches.

There was a full set of testers for $15 the last time I checked. (10,12,14,18,22,24)

I'd say that is the best bet until you are confident you can make it. I know I'm not there yet, but hopefully someday I'll get there. In the meantime, I'll just pay for what I know to be perfect and concentrate on other things.

I hope that made sense. :D
 
Have you cooled the solution down to below zero degress C and filtered? This will help drop out as much salt as possible leaving you with more nitric acid in the solution. The only other way that I know is careful distillation.

Like Noxx, I too make nitric from sodium nitrate and 33/100 battery acid. I have a lab still & tried to still it off. Nothing happened at 83C (boiling point of nitric acid) The condenser didn't even get wet untill untill I slowly raised the temp to 100C and got the water to boil.

I am boiling off some battery acid (without the sodium nitrate) right now to use in Steve's recovery cell I'm putting together. But I would like to know the trick to getting nitric acid to come out of the dumb thing.

Battery acid is cheap at NAPA. Last time was $11 something for 5 gallons.
 
Phillip,

It may make more sense if you knew that the information quoted was nearly the last step in a multistage procedure. I had already discussed this with Noxx in a PM a while back.

The reduced temperature will force any dissolved niter salts to precipitate out of the solution as sulfates leaving the nitrate portion of the molecule behind. It stands to reason that if an ion is dissolved in a solution the acidic molecule it is bond to won't be free to form the desired acid.

Here's a solubility chart that I calculated the reaction around:

solgraph.jpg


The idea was to dissolve the nitrate in the minimum amount of warm water, cool to room temp, add the sulfuric acid, then bring the solution temperature down to drop the least soluble salt. What remains is a small quantity of the original nitrate in dilute nitric acid with a touch of the resultant salt.

Steve
 
A crazy idea - maybe.

I spent a couple of years experimenting with ion exchange membrane cells. They are basically ion traffic controllers. You can buy membranes that only pass negative ions or, those that only pass positive ions or, those that pass no ions, etc. In the Shor refining machine, I think he uses one of these membranes. It's in one of his patents.

I've worked out a way to make pure nitric plus water with a membrane cell. It's basically 3 or 4 inline plastic chambers, with membranes in between, and electrodes in the end chambers. The chambers all contain liquids.

Sodium nitrate is in one chamber. The nitrate part of the sodium nitrate is pulled into another chamber by the current. The hydrogen ion generated at the anode is also pulled into the same chamber from the opposite direction. The result is H+NO3 - Nitric acid.

They use these things for desalinization. The Na+ and the Cl- are pulled out of the water, to other chambers, in different directions.

I know that this will work from past experiences. No doubt. It can be made to any strength. The longer it's on, the stronger it gets. The problem is in finding a membrane that will stand up to strong nitric. I'm still looking. I may be able to use a flower pot with the hole sealed up. The old fizzer cells, which were membrane cells for making gold chloride with strong HCl and current, used unglazed clay pots as the membrane.

This would be very cheap to set up. The biggest cost would be the power supply.
 
I'm still studying your chart. Good job. You've been busy in the CRC Handbook, it looks like.

Sorry Steve. I started typing my long post before you posted your great chart. I didn't mean to rain of your parade.

I'm now reading my Chemical Dictionary on how they make nitric acid. One of the methods sounds interesting. They start with weak nitric acid. This is neutralized with soda ash, evaporated to dryness, and treated with sulfuric acid. Synthetic niter cake - NaHSO4 - precipitates out as a by product and, I guess you're left with conc. HNO3. I'll work out the equations. Sounds simple and cheap.

WOW! I just caught on!

The more I read this, the more I realize that it's EXACTLY the same process you're working on, Steve! You're starting with sodium nitrate. They're making sodium nitrate in the first step. Everything else sounds the same. The only difference is that they add the H2SO4 to DRY sodium nitrate. Wouldn't this be better? Wouldn't you end up with stronger nitric? May I ask where you got your process? Does this process have a name? I love this process. This is very exciting.

If you were to use concentrated sulfuric, not drain cleaner, and dry sodium nitrate, there would essentially be no water in the system. You might end up with red fuming nitric, which wouldn't be good. To make 68%-70% nitric, by weight, which is about tech. grade strength, you would have to add some water somewhere. Have you done the equations?

To get out most all of the salt, you're chilling it. The process in the book gets it all out by having a non-water system. The salt is NaHSO4, sodium bisulfate, which, to have excellent nitric, you must get rid of. There must be a middle ground. Terribly exciting. Have you tried this?

Ideally, the way to do it would be to make it without water, to get rid of all the salt, and then dilute. However, the red fuming nitric might drive you out of the building, or the county.

Have you posted any other info about this on the forum? I think you have. Can you find it and give links. I didn't pay much attention because I thought it was a distillation process you were talking about, which I hate. I apologize.
 
Chris,

It came from the space between my ears! :lol:

I have not tried it yet. It's something I cooked up for Noxx last month in a PM. When he replied about his success I realized he took some shortcuts and made a few measurement errors (no offense Noxx :wink:, you did great ). I had considered going dry but you've already pointed out the pitfalls of that idea. The idea is to use the least amount of H2O to dissolve the niter. This is accomplished by temperature control, hence the chart. Yes, I've done the math on this one. No it hasn't been made public.

Steve
 
Not understand all the chemistry you guys are talking. The girls, I understood back when I should have been paying more attention to education. Now I'm paying!

ANyhow. I stilled off some sulfhuric acid. "no more water." I added sodium nitrate pellets. They did not dissolve, even when heated. I had to add it to a little of the water I stilled off, and heat, to dissolve the pellets. The pellets made heat when mixing. It is no where near "Red Fuming"

It will eat metals, but could be a lot better.

From what I gather here is to now freeze it, and filter it.

At what point do I plug the cord in? :roll:
 
Steve,

Here's the equation:

NaNO3 + H2SO4 = NaHSO4 + HNO3

Here's the weights in grams, rounded off, for the reaction to produce 1 liter of 70% nitric acid. This assumes that everything is anhydrous which, of course, it isn't. I have included the 30% water in the nitric on both sides. More water than this will be needed to dissolve the NaNO3 so, the nitric % will be less. Also, there's water in the sulfuric to consider.

1330(NaNO3) + 1533(H2SO4) + 422(H2O) = 1878(NaHSO4) + 986(HNO3) + 422(H2O)

One liter of 70% nitric weighs about 986 + 422 = 1408 grams

The salt, NaHSO4, sodium bisulfate, is strongly acidic when dissolved. It's used for toilet cleaners (Sani-Flush is 75% NaHSO4), lowering the pH of swimming pools, a safer sulfuric substitute in school labs, and an acid pickle for silver castings.

NaHSO4 is very soluble in water, even at 0 deg C. Here's the solubilities: 500 gm/L at 0 C., 670 gm/L at 22 C., and 1000 gm/L at 100 C. If you plot those out, it curves down to the left and seems to hit zero at about -80 C. This happens to be the temp. of dry ice. It seems like, if you used dry ice, you could get all of the salt out. The problem is, nitric freezes about -42 C. and, this figure is probably for 100% nitric. For 70%, it would be higher. There is most likely a low temp to maximize salt dropout without the nitric freezing. You could use a thermometer.

On the net, with the little amount of info that I could find on the process you're doing, they required distillation to get rid of the salt. Of course, they didn't think about chilling it.

The solubilities, above, are for the salt dissolved in water. In the presence of the high nitric acid, the solubilities might be a lot less.

All in all, we don't need 70% nitric acid for most any of our processes. For dissolving silver, copper, etc., a 50/50, nitric/water, mix of commercial 70% nitric, cut by volume, is the most efficient mix for dissolving. This figures out to 41% nitric by weight. For aqua regia, I usually add about 10% water, for effeciency. I could use a weaker nitric, add no water, and end up with the same thing. The nitric for this purpose would be about 53%, by weight, assuming a 3/1, HCl/HNO3 mix.

Also, if the nitric % is high enough, the presence of some of the salt in the solution might not interfere much with our processes. This would require experiments.

I downloaded a couple of old industrial chemical books on Google Books. I found another process. Instead of sodium nitrate, they used barium nitrate. The equation, otherwise, is about the same. It takes about 1.5 times as much weight of Ba(NO3)2 as it does NaNO3. The big difference is that Ba(NO3)2 is only about 10% as soluble in water as NaNO3. Therefore, the nitric yield was only about 10%, by weight. They said you could boil it to raise it to 25%, the point at which HNO3 starts coming off. The 25% would work for our processes but, not as fast. The beauty of using Ba(NO3)2 is that the resulting salt, BaSO4, is zero soluble in everthing and, therefore, could be completely removed at room temp. About the cheapest I found barium nitrate was from pyrotechnic chemical companies, for about $3.30/pound. That was for one pound quantities. They couldn't ship it, so you had to pick it up.

Steve, unless I made mistakes, those are the numbers. I wish I had a lab but, I don't. If you need help or advice, I'm here. Please keep us posted with your progress. As you know, this process could be very important to all the members that can't get nitric acid.
 
Sorry about all the chemistry talk, PhillipJ. Steve's process could be very important to all members and, we have to get the numbers right. When finished, the process will be much simpler.
 
Here is a link to platinuminfo about nitric acid making.
http://www.platinuminfo.net/app_ind_na.html
maybe there will be something in what they say that will
help. They say platinum or rhodium gauze is used in the
Ostwald process.
I don't understand all the chemistry talk, but cheap or even
available nitric would be a help to all of us, so thanks guys.
Jim
 
Back
Top