Concentrate Nitric Acid ?

Chris,

Nothing appears wrong with yours a first glance, except in mine I'm not leaving any Hydrogen behind as follows:

H2SO4 + 2 NaNO3 --> Na2SO4 + 2HNO3

The big difference in my recipe is the solubility of the sodium sulfate salt (as opposed to sodium hydrogen sulfate you produce) and the fact that my equation yields twice the nitric acid at a higher temperature ( no dry ice, just salted ice ). :wink:

I've run the numbers like you did and ended up with about 160 mL of 50% nitric (give or take a few percent) for a single mole of 96% sulfuric and using 100mL H2O to dissolve the nitre.

I won't bore everyone with the math, but here's my summary (PM me to see all the factors I used to derive this reaction):



Reaction:

-Bring 100 mL of Distilled Water in a 500 mL pyrex beaker to 100 C
-Add the Nitre of your choice (202 gm K / 170 gm Na)
-Stir until Nitre is completely dissolved, let cool below boiling
-SLOWLY add 56 mL conc (96%+) Sulfuric Acid to Hot Nitre solution while stirring, DON'T allow the solution to boil!
-Allow solution to cool to room temp (DO NOT SKIP - VESSEL WILL SHATTER IF PUT ON ICE WHILE HOT!!!)
-When vessel reaches room temp (25 °C) put the vessel in the freezer or on a salt water ice bath
-Let stand until temperature of mixture reaches -5 °C
-Let stand at -5 °C until all precipitate settles
-Pour the COLD solution off into glass container with tightly sealed lid DO NOT POUR OFF ANY OF THE SALT IN THE BOTTOM!!!
-Makes ~160 mL ~50% HNO3



Steve

Here's a very interesting tidbit I just noticed on wiki while reviewing the sodium sulfate salt produced by the above reaction:

http://en.wikipedia.org/wiki/Sodium_sulfate#Other_applications

Pay very close attention to the last paragraph of this section (Other Applications). We may have an excellent processing cycle in the works here. One that may even allow us to recycle the by products for reuse. :idea:

Steve

They both are valid equations and both are reactions of the same 2 starting chemicals. The quantities of the 2 chemicals is what makes the difference. You went in one direction and I went in the other. I don't think either of us realized the other direction existed. I know I didn't.

However, to produce all Na2SO4, the quantities of H2SO4 and NaNO3 must either be perfect or short on sulfuric. If any extra H2SO4 is present, it seems the NaHSO4 will form, as in the Wiki link you just gave. Check the first equation under "Physical and Chemical Properties", near the top. Do you read this the same way?

I notice that you are using conc. H2SO4. What about using the drain cleaner? It would be touchy but it could be done. You need a method of analyzing the drain cleaner. This could be done in a few minutes with a scale and a small vessel to measure some sulfuric fairly accurately. An inexpensive graduated cylinder would be good. Measure the sulfuric out accurately, weigh it and calculate the density. Look the answer up on a chart and it tells you the concentration. You could easily get within 1%-2% accuracy.

Of course, making sodium sulfate would be better than making sodium bisulfate.

Exactly how I read it as well.

Read my post again. I added to it.

I merely specified the percentage to set a reference point for the molar calculations. Any concentration above 90% would be fine, you just need to adjust the input volume. The extra water can begin to dilute the product if you go much lower in concentration. Luckily sulfuric is the easiest of the mineral acids to concentrate!

Steve

Hi Steve:

A great piece of work on comming up with a safe and easy method that us neophytes can make an acceptable Nitric Acid.

I just read this post last night and decided to try to make a batch of Nitric acid with this formula.

I made a batch today with good results. The only difference was, I came up with a different total amount of nitric acid. After taking it down to approximately -5c. and carefully pouring off all liquid, I wound up with 130 ml. I may have poured it off too quick.

I immediately poured some on some small semi-gold plated pins and the acid went to work immediately. In just a short time it had disolved all of the non gold metals.

I have been making a very weak nitric acid with concentrated sulfuric acid and sodium nitrate by letting it sit over night and pouring it off.. There was always about half the sodium nitrate left and the resultant acid was very weak. It took several days to disolve small gold pins.

Your method and formula is certainly appreciated and as always, thanks again for your many contributions to this forum.

I have an old say "Nothing happens accidentally"

Thanks again,

Catfish

PS Thanks to Cris for his input also.

Catfish,

Thanks for the feedback, I'm glad it worked for you. Did you use Potassium Nitrate or Sodium Nitrate?

This would have been a great tutorial, you may have been the contest winner had you entered it as a tutorial, it's not too late.
:wink:
Steve

Steve:

I used Sodium Nitrate (16%) and contcentrated sulfuric acid (battery acid from NAPA) that I boilded down to Specific Gravity of 1.8 Grams per 1 ML. I found that commerical battery acid is 65% H2O and 35% of 98% Concentrated H2SO4. I measured the SG of the the Battery acid and found it to be 1.25 SG and then boiled 1000 ml of the battery acid down to 360 ML and remeasured the SG and it came out to be 1.80 SG per 1 ml. 1.84 sp per 1ml at 25`C would have been 98%. Unfortunately I dont have any specilized laboratory equipment for precise measuring of the specific gravity and concentration precentage of this H2SO4, but my calculations puts it in the 90+ % range.

I have been using this acid in my Electrolytic cell. It is absolutely clear, no special additives or inhibitors, and works extremly good.

Keep up the good work Steve. I enjoy reading all your posts and find not only do they make interesting reading, but are also very informative. Steve, too often we see folks that are extremly knowledgeable but do not possess the verbal or written skills to explain thier ideals. You have a very good understanding of gold recovery and refining principals and technical theory. You are also very good at being able to convery your thoughts and ideas to others in layman terms to us neophytes, inorder that we not only understand them, but we can put them to practical use.

Thanks again,

Catfish

All,

I put my thinking cap on at lunch today and fine tuned my original nitric acid recipie from yesterday's post. I'm running the numbers one more time and will be posting a new and improved, never before seen, version of the experiment. The chemicals are readily available, safe, and the reaction produces a product that is more concentrated than the previous version of the experiment. Stay tuned gold diggers!

Catfish,

Thank you for the kind words, they make my efforts all that much more rewarding!


Steve

Catfish and everyone else,

How long did it take to boil down the battery acid? Did you actually boil it? If you did, I'm sure you noticed that, the stronger it got, the higher the boiling point. In fact, 98.3% sulfuric acid, by weight, boils at 640 deg. F. I can't imagine anything more dangerous than 640 degree concentrated sulfuric. Since the sulfuric holds the heat, it's easy to let the temp. rise that high, on a regular hotplate. Be extremely careful. Rethink how strong you want to get this stuff and how hot you want to get the temp. At a lower temp., it will take a lot longer but, will be safer.

Put the vessel that you're heating the sulfuric in, inside of a larger heatproof container, in case of breakage or spills. The best arrangement I can think of is a beaker inside of a 5 quart, white, flat-bottomed, Corning Ware dish. Of course, you don't need the lid.

Also, around 98%, you start giving off sulfur dioxide fumes. Did you smell this?

I've done a lot of what's called "wet ashing", using very hot concentrated sulfuric. This is used to dissolve organic materials (think skin). For example, I used it for vacuum filter papers that had small quantities of gold powder stuck to them. The wet ashing totally dissolved the paper, leaving a clear solution with the gold powder on the bottom. This was for assay purposes and not for refining. I have also dissolved a few dead flies, grasshoppers, etc., in my life. BTW, this is very dangerous and I haven't told you the whole procedure because I don't want you trying it. It won't work as I gave it. I'm just trying to illustrate the dangers of hot strong sulfuric.

Goldsilverpro:

You are absolutely correct about the boiling temp of H2SO4, My book sez 338C or 640.4F at 98.3%.

I heat the NAPA battery acid in a pyrex bowl on a hot plate out side. I also place the hot plate and all in a foot tub in case of breakage. (this also keeps the wind from effecting the heat) I heat the H2SO4 at 230` F with a good quality thermometer, monitoring the temp at all times. My objective is to reduce the h20 only. When I start this process, I weigh 1.0 ml of battery acid in 10 ml test tube on my gold scales after zeroing the scale with an empty test tube. I also then weigh 1 ml of distilled water and determine the Specific gravity of it which always comes out to be 1.0 SG. I always come up with 1.20 to 1.25 SG on NAPA battery acid. This is about 65% h2o and 35% H2SO4. Keep in mind I dont have a pycnometer to a be able to make a precise measurement. But this is close enough for me. Also I don't crank in the temp correction factor of .0023.

It takes me about 1 hour to boil off the required amount of water. At 230 degrees it will eventually stop boiling and condensing. There are never any odors that come from this process. After it cools to room temp, I then take 1 ml again and weigh on gold scales. It just about always comes up to 1.8 + or - .1, specific gravity. Keep in mind my scale has a + or - accuraticy of .1 gram. I then measure the volume of the remaining acid and it usually comes out to about 360 ml + or - 10ml, when I do a 1000ml in a batch.

I have done several different batches of different volumes and they all come out the same. Just the boiling times are different. I have no way to actually measure the precent of concentration of the remaining sulfuric acid. All I can do is determine the approximate precent computation by using the formula of 1.84 SG at 98.3% concentration., and do the math to come up with my precentage of concentration.

You have heard the term, " necessity is the motherhod of invention". Well I dont like all the additives and inhibitors in the drain cleaners and this is the reason I came up with this method. I buy the NAPA battery acid for $4.80 plus tax for 1.5 gallons. This will make about 2 quarts of pure 90+ % concentrated sulfuric acid for my cell and to make Nitric acid.

Catfish

Catfish,

I think your method is excellent, very well thought out, and scientific, yet practical. You call yourself an amateur but, I think you are underrating yourself and your method of approach could teach us all a thing or two. Steve is right, you should do a tutorial on this. It could very well win.

Catfish. You seem to think a lot like I do. Except I boil my acid in a lab still on a gas stove on low flame. It takes maybe 12 hours to get all the water off. I can tell it's done when the condenser shows few droplets. What goes in the catch jug makes a unique flavored coffee.

I tried making nitric acid with drain cleaner and found that it is best left as drain cleaner. The NAPA acid is good stuff and even cheaper in the 5 gallon jug they sell.

Haven't tried Lazer's recipe out on anything yet and am hoping it works better then the old way of just pouring the 33/100 sulphuric acid on NaNO3. When doing pins, the copper chrystals formed and clogged the whole works up and I had to add hot water to get the gold flakes out.

Also, I am assuming that the settled sodium nitrate is pretty much spent, and cannot be reused to make more nitric acid.

1st batch of distilled sulphuric acid went to my new recovery cell. It works so well I took a week off work to play with it. If I do it right, I can make smoke come off of it. Too cool! (Thanks Lazersteve & GSP for all your help here).

Hey Guys,

Do you get the acid at the local NAPA or do you order from a warehouse? I've got a NAPA store at the end of my block. Do you have a stock number for the 5 gallon size?

I agree with the cleaner is better mentality, but I tend to take shortcuts just like everyone else when I'm in a rush. The drain opener is fine for the cell, but I think the boiled down battery acid will do better for the nitric experiment.

Unfortnately, I misplaced my 98% conc Sulfuric a few years back along with a gallon of conc HCl and 2 quarts of battery electrolyte that I picked up at the local battery rebuilding shop. I was moving everything out of my old shop into a new bigger one and I think they all got put in a box that ended up in a dumpster.

I'm think I may devise a new recipie to make my own 'homemade sulfuric acid' . The experiment that readily comes to my mind may be a little too advanced for the forum (handling gases and all) so I'll have to seriously consider if I should post it or not. Who knows maybe I will have another brainstorm and devise a safe way to make sulfuric acid too. :?: :idea: :!:

Keep up the great posts!

Steve

Hi Steve:

I buy my battery acid from Local NAPA store. It is a stocked item and the Technical info is "Battery Fluid, Acid, UN2796. Casa Number Cas #7664-93-9 and of course the added water. It is 1.25 Specific Gravity and is manufactured by Colonial Chemical Company.Tabernacle, NJ.

It is 65% H2O and 35% H2SO4.

I buy mine in 1.5 US gallons or 5.68 Liters at 4.80 plus tax.

They have it in one quart quanity or you can special order 5.0 gallons. I pefer the 1.5 gallon size, it is not too hard to work with and it is much easier when you have to pour small quanities.

Steve, what I really like about it is that it is pure and no additatives or inhibitors added. It stays very clean and you don't wind up with as much junk in your cell when you are through.

Of course I reduce the water content and get it upwards to 90% plus before I use it.


catfish

We need a spell checker on this machine>

I remember paying $11.oo something for 5 gallons. They had it right at the store both times I got it. And yes, the smaller size is easier to handle. The stuff almost needs to be carted around in 5 gallons. Heavy!

Thanks guys I'll pick some up by the end of the week.

Steve

I get the 5 gal size at Napa as well. Here in Ohio it cost about $13. out the door. They usually have it in stock unless I want more than 5 gals then it only takes a day to get more if I ask.

This thread begin by strong HNO3 and end with strengthening H2SO4.

I joust want to notify that the protocol to concentrate HNO3 use to be:

Diluted HNO3 to which you add concentrated H2SO4, then distillation in glassware.

The main idea it's that HNO3 is "bond" strongly to water, in fact it's the dissolution energy that we have to provide. At this level, water get out with HNO3, so we have to add H2SO4 to force the water to stay behind. I guess that H2SO4 also compete with HNO3 for solubility.

In all case those distillation are very hazardous I would not try it myself. If there other way... I'll choose it.

For the ion exchange membrane... a bit more about that would be very interesting.

Where can we buy them? Which kind of electricity can we involve? (12V, 100V, 1KV?)

This can be a very cool solution for treatment prior to extraction, you create an acid bath to dissolve copper and the rest, and remove it from the solution as it dissolve...

maybe we can start a thread on membranes, I'm very interested since it can also be very ecological (less solution to throw away)