cold nitric recipe, another observation

[au-artifax]

Hello all. First off, I really enjoy the ease of making nitric with Steve's recipe. It is simple and quick.

On time though, I didn't get quite the output expected. I followed the recipe to the letter as always, and I use KNO3 to do mine and have had no issues. This particular batch I did by weighing the sulfuric and KNO3, which I find easier than doing volumetric with one and weight with another. Also, I kept the mixture down to -10C overnight with great crystalization and clear product, slightly yellow and very reactive.

Here's what I did though: I took the leftover crystal mass, added 200ml of distilled water to the same reaction vessel, heated till all was disolved again, yada yada, same process, and I got a whole nother batch with slightly more output than the first.

After the first batch the crystals were yellowish, but the second, they are almost white... just a hint of yellow.

I tested the reactivity and great results processing the material a second time.

The one thing I did not do yet, because I am doing a third round, is do a specific gravity test on all three batches combined.

Has anyone ever re-processed the cold nitric recipe like this? And for anyone who asks about the amounts used, I used exactly the ratio the recipe asked for, but doubled.

Is there anything else I should be thinking about here that might be a good idea? I think maybe it would benefit anyone who does this recipe to consider running the process again by adding some more DW.

Comments?

 

[butcher]

Sodium nitrate does not have the same problem KNO3 does, the sodium sulfate salts are smaller crystals they do not trap nitric acid like the potassium sulfate salts can, If the nitric acid is cooled too fast with the potassium sulfate salts forming quickly most of the nitric acid can get trapped in the crystal structure of the salts, very slow cooling can help to slowly form crystals and thus trap less of the nitric acid in the potassium sulfate salt.

 

[au-artifax]

Sodium nitrate does not have the same problem KNO3 does, the sodium sulfate salts are smaller crystals they do not trap nitric acid like the potassium sulfate salts can, If the nitric acid is cooled too fast with the potassium sulfate salts forming quickly most of the nitric acid can get trapped in the crystal structure of the salts, very slow cooling can help to slowly form crystals and thus trap less of the nitric acid in the potassium sulfate salt.

Yes butcher, that is exactly what happened, and thank you for cluing me in on how kno3 reacts. In fact, I transfered the reaction vessel from around 50°C to a -10°C ice blanket directly.

I will try it slower like you said next time.

Thank you.

 

[au-artifax]

Sodium nitrate does not have the same problem KNO3 does, the sodium sulfate salts are smaller crystals they do not trap nitric acid like the potassium sulfate salts can, If the nitric acid is cooled too fast with the potassium sulfate salts forming quickly most of the nitric acid can get trapped in the crystal structure of the salts, very slow cooling can help to slowly form crystals and thus trap less of the nitric acid in the potassium sulfate salt.

And one more quick question; do you thing I should let it cool slower to roomtemp.also, as I saw crystals forming before it reached room temp, and that is the point where I iced the batch.

 

[butcher]

First I make sure that all salts are dissolved before cooling it back down to room temperature, this way the nitric acid and potassium sulfate salts are both in solution, to insure a complete reaction of all of the potassium nitrate with the sulfuric acid solution.

Much of the potassium sulfate salts will form after lowering heat from the initial reaction, slow cooling to room temperature, and a stir to bust up crystals, I decant the nitric acid from these initial salts before freezing (where more salts will form), because the solubility of the potassium sulfate being lower at these colder temperatures.

 

[rickbb]

I hate to bring back old threads, but;

I'm using Steve's cold recipe for the first time. He states to boil 100 ml of water then stir in 202gm's of either potassium nitrate or 170gm's sodium nitrate, I'm using potassium. (Spectracide Stump Remover, MSDS says its 100% KNO3.)

So far so good, I've added in the KNO3, stirred until it has completely dissolved, but, when it starts cooling off the KNO3 is precipitating back out. The cooler it gets the more KNO3 crystals form.

I need more than that what his recipe he has posted, so I doubled all the quantities, 200 ml water, 404gm's KNO3 and was going to use 112ml of concentrated sulfuric acid to produce a yield of ~320ml 50\50 nitric.

Obviously I've done something wrong here, can anyone point me in the right direction? Was I wrong to assume that a simple doubling of the water and KNO3 would work? It seems I'm over the saturation point of KNO3 in the volume of water since it precipitates back out when cooled.

 

[FrugalRefiner]

So far so good, I've added in the KNO3, stirred until it has completely dissolved, but, when it starts cooling off the KNO3 is precipitating back out. The cooler it gets the more KNO3 crystals form.

Rick,

You may be letting it cool too much. According to Steve's instructions, you don't let it cool to the point that the nitrate would start to recrystalize.

-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!!!)

He came up with the amounts involved to create the strongest acid possible, so the nitrate solution is used hot to minimize the amount of water in the reaction.

Dave

 

[Barren Realms 007]

I hate to bring back old threads, but;

I'm using Steve's cold recipe for the first time. He states to boil 100 ml of water then stir in 202gm's of either potassium nitrate or 170gm's sodium nitrate, I'm using potassium. (Spectracide Stump Remover, MSDS says its 100% KNO3.)

So far so good, I've added in the KNO3, stirred until it has completely dissolved, but, when it starts cooling off the KNO3 is precipitating back out. The cooler it gets the more KNO3 crystals form.

I need more than that what his recipe he has posted, so I doubled all the quantities, 200 ml water, 404gm's KNO3 and was going to use 112ml of concentrated sulfuric acid to produce a yield of ~320ml 50\50 nitric.

Obviously I've done something wrong here, can anyone point me in the right direction? Was I wrong to assume that a simple doubling of the water and KNO3 would work? It seems I'm over the saturation point of KNO3 in the volume of water since it precipitates back out when cooled.

I haven't used potassium nitrate only sodium nitrate. You will get a lot of crystals as the solution cools down to ambient temperature and more will form when you cool it down to freezing as recomended. I would suggest you make twice of what you think you need so you can filter the liquid that you pour off after the solution has set freezing over night. A trick that you can use is to filter the crystals after it reaches ambient temperature then take the filtered liquid and freeze it then filter again.

 

[rickbb]

Oh crap your right.

I even have the recipe up on my laptop here in the shop and still only saw the "let cool to room" temp. But that's for AFTER I add the sulfuric.

My bad.



Maybe I need some remedial reading lessons. sigh.

EDIT: correct spelling and to add;

Thanks Dave, all good now. Have a nice bright dark yellow solution cooling off.

 

[rickbb]

OK, I guess I did something wrong after all. The solution is not quite down to room temp yet and I have a large amount of precipitate in the bottom. It started out looking like crystals, long ice like formations. I broke them up and stirred it all and now it looks granular.

This after adding the sulfuric acid and letting cool.

What I did;

boil 200 ml of di water, while boiling stir in 404gm KNO3 until dissolved, turn heat down.

When boiling stopped and solution was still hot and clear, slowly added 112ml concentrated sulfuric acid, stir and turn heat off. Stirred a few more times then let sit.

When I noticed some precipitate, checked temp and it was about 105F, I stirred and broke up the precipitate several more times. It's now just about room temp and I have granules of something up to the 300ml mark.

Is this normal? From what I've read you get the precipitate after you freeze it, haven't seen any mention of it at room temp.

Here is a picture;

http://i24.photobucket.com/albums/c7/rickbb/20140927_181117.jpg


Edit: change pic link

 

[Barren Realms 007]

Looks normal just not as much crystals with sodium nitrate.

 

[rickbb]

Thanks Barren,

After some gentle prodding from a nice fellow, (thanks Dave), I went back and re-read the posts and this time I realize that the answers to all my questions were right there in front of me. (I blame that speed reading class I had in high school, spent too much time skimming and not enough time understanding.)

I just took the solution out of the freezer and poured off 125ml the rest of that beaker is white frozen solid crystals and granular salts.

I plan to let it melt overnight and filter it off tomorrow and re-freeze to see if any more is in there. I was using stump remover, perhaps it was not up to the task. I have some tech grade KNO3 I will try on my next batch.

Rick

 

[Shark]

I have used Spectricide Stump Remover several times, and the second round seems to produce slightly better than the first. I prefer Sodium Nitrate, as it does form fewer crystals, and they seem to be a bit larger, and easier to filter out. Doing a twice filtered solution as Barren suggests helps. I place the first filtration in one container and the second in it's own container. I am not sure why I do this, as they both seem to work well. Your picture of the salts settled out look normal for a Potassium based nitric. I work with such small amounts of materials that I have never been able to justify the purchase of actual Nitric Acid, and have always used my home made variety and been pretty happy with it. The one thing I find is the slower I add the Sulfuric Acid, (with a lot of stirring), the better the Nitric Acid seems to be.

 

[rickbb]

Just an update and a thanks to those that pointed out the obvious things I missed in reading the posts here.

I ran 2 batches and now have ~550ml of nitric.

One batch with the stump remover made a very yellow liquid (~300ml), and a batch with tech grade from a lab supply company made a crystal clear liquid, (250ml).

I tested it with a small sliver of ~997 Au. At room temp the reaction was not visible. Even after 48 hours it had not dissolved, it was blackened, but mostly intact. I put some heat under it and the reaction was very clear and the sliver was gone in less than 5 minutes.

Maybe someday I'll invest in some hydrometers and graduated cylinders to measure the SP to find out the strength that I'm making but as long as I'm following a known recipe and it does the job that's what matters. (And I'm learning something to boot.)

 

[joekbit]

Well, where is Steves' recipe? There are now 15 posts here, 1 is mine and none of them Steves'. The first post how he enjoyed the ease of making it :?:

 

[jimdoc]

Well, where is Steves' recipe? There are now 15 posts here, 1 is mine and none of them Steves'

http://goldrefiningforum.com/viewtopic.php?f=60&t=14040&p=143214&hilit=nitric+recipe#p143214
Fixed link Steve

 

[joekbit]

Well, where is Steves' recipe? There are now 15 posts here, 1 is mine and none of them Steves'

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=14040&p=143214&hilit=nitric+recipe#p143214

Wow,,,lol,,,that was quick. I like that kind of service

Thanks
Joe

 

[jimdoc]

Well, where is Steves' recipe? There are now 15 posts here, 1 is mine and none of them Steves'

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=14040&p=143214&hilit=nitric+recipe#p143214

Wow,,,lol,,,that was quick. I like that kind of service

Thanks
Joe

The search box is quicker.

 

[joekbit]

Well I did my first batch with Steves recipe. Went well. I used NaNO3. I see at least 1 person ran the salts a second time, so I did the same. Not sure how it will come out right now, it's in the freezer. Any idea on just how many times you can use the salts? That would be nice to know. How can we tell if we have exhausted all the nitrate in the salts?

Corrected mistake, had NaNO2 now NaNO3

 

[butcher]

Using the recipe properly you will not have nitrate salts left to reuse, Laser Steve done a good job of calculating moles needed for the reaction and conversion, your salts would be sulfate salts (that could possibly hold some trapped nitric acid depending on how you performed the reaction, a little water will pick up any trapped nitric acid), the sulfate salts can be reused in other chemical reactions where you may need sulfates.

Reusing the sulfate salts they cannot be used again to make nitric acid.

Unless you made bisulfate, from using too concentrated sulfuric acid, and less nitrate salt in your reaction, then it has a hydrogen that can act similar to sulfuric in a chemical reaction.

I am not sure what you mean by reusing your salt, but if you do not have sodium bisulfate NaHSO4, and have sodium bisulfate Na2SO4 as a byproduct, you cannot reuse it to make more nitric, at least not the way I think you may be trying to.