# Nitric acid not condensing.



## Mmbullion1776 (May 27, 2019)

I’m running a simple distillation apparatus 1000ml round bottom flask, with Liebig condenser. I have 400grams of 98% potassium nitrate and 400 grams of 98% sulfuric acid in the flask reacting over heat. My thermometer says about 170f. I know that’s not exactly as hot as it should be. The problem is the reaction seems to be going fine but the cloud of nitric gas is just hovering around the condenser not going down it turning into liquid. The water running through it is ice cold I don’t know what the problem is.


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## Lino1406 (May 27, 2019)

To me it looks not "nitric gas" but NO2


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## Mmbullion1776 (May 27, 2019)

I’m sorry I didn’t use the correct term I’m pretty sure that’s what I meant. I’m really bummed out about this, I have watched the process over and over and I thought I did everything right. I called my friend who has taught me the most and he believes my temps aren’t high enough or the condenser is to warm.


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## Mmbullion1776 (May 27, 2019)

Not condensing.. Going to pack ice around it.


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## butcher (May 28, 2019)

with that ratio of nitrate to sulfuric acid you will be fuming off NOx gases at about half that temperature, the fume will continue until you vapor off all of the solution...

The ratio is too concentrated you would need more dilute acid.
Too concentrated for refining, with this I am hesitant to help, why so concentrated? it has no use in recovery or refining,...
You have plenty of gas and not enough water in the solution, the gas would dissolve in water, a little hydrogen peroxide will help, bubble the gas, the smaller the bubbles, the longer the contact with water the more the gas will go into solution as nitric acid.

NO + air = NO2
NO2 + water = HNO3
even the water in your lungs nitric acid will form with this gas...


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## Lino1406 (May 28, 2019)

Sorry, N2O5 + water ,= HNO3


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## Mmbullion1776 (May 28, 2019)

butcher said:


> with that ratio of nitrate to sulfuric acid you will be fuming off NOx gases at about half that temperature, the fume will continue until you vapor off all of the solution...
> 
> The ratio is too concentrated you would need more dilute acid.
> Too concentrated for refining, with this I am hesitant to help, why so concentrated? it has no use in recovery or refining,...
> ...



First off butcher let me say I APPRECIATE you coming on my posts, and trying to help me learn. Not just correcting me and my terminology then not telling me why it is you are correcting me. 
I was hoping to dilute later to 68% I’m going to show you 2 links on where I have gotten my process from. If you have time to look at them. 
https://m.youtube.com/watch?v=DJ7D4FOUMQw
And the end of this one. 
https://m.youtube.com/watch?v=2yE7v4wkuZU
I’m also using some information I’ve learned from other places and people. Including Cody’s lab. I know I am such a noob I try to read as much as possible and educate myself. I practiced for almost 8 months before I tried this today. It was really overwhelming and sad it didn’t work the way I thought it would. Again I REALLY appreciate the time you take to reply to me and guide me in the right direction. I can only read so much on my own, it doesn’t help when I don’t have an outlet for my questions. I felt really intimidated asking this today as a lot of you guys have knowledge I hope to one day come close to.

EDIT~
I have done some reading and I understood what you are saying the ingredients being so dry is definitely a problem. I got a few things wrong that’s for sure. I will try again tomorrow with some distilled water.


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## butcher (May 28, 2019)

There is no need to make fuming nitric acid it has no use at all in refining.

When water or a less concentrated sulfuric acid is used you will have water involved in the boiling reaction, this water will vaporize along with the decomposing nitrates which form the NOx gases and they will then combine and condense back into nitric acid when cooled in the condenser.

Water can be in a receiver vessel and then the NOx gases can be bubbled through this water, hydrogen peroxide would provide oxygen to help convert NO gas into NO2 gas, then NO2 gas and water will combine to form nitric acid. 

Note methods above are slightly different but produce the same reaction and results. 
The first one is using the condenser with the water vapors and Nitric oxides condensing together in a water-cooled condenser, the second setup we are bubbling the gases from the boiler through a cold water solution in a receiver vessel.


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## rickbb (May 29, 2019)

Mmbullion1776 said:


> I was hoping to dilute later to 68% I’m going to show you 2 links on where I have gotten my process from.




You can't dilute it down to 68%, 68% is the highest you will ever get outside of a very highly specialized lab. 

I think you need to slow down a learn a bit more, you have enough brown fumes there to, well, just stop. Please.

edit to fix errors.


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## Mmbullion1776 (Jun 3, 2019)

rickbb said:


> Mmbullion1776 said:
> 
> 
> > I was hoping to dilute later to 68% I’m going to show you 2 links on where I have gotten my process from.
> ...



I’m curious isn’t what I am doing learning? How does one learn without practicing the procedures. I am doing the best I can I am reading as much as I can. I understand that i need 68% nitric acid. I understand that it is an azeotrope, and I shouldn’t worry about getting anything stronger. You know I come on here to learn, I want to be safe I want to be successful and I know this is a good place to start. It’s really hard when someone tells you “you need to learn more” then not even attempt to point a finger in the right direction. At least butcher tried to help me. I think I am about done here, I have come to learn but it seems like there are few willing to teach or point in the right direction. I thought this was the right place a forum where I could grow and learn, but I’m starting to wonder and it makes me really sad cause I have put a lot of heart into this. Thanks.


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## butcher (Jun 3, 2019)

Take a breath, but do not breath those RED fumes, Re-LAx.

You can make fuming nitric acid, and distill 98% nitric.
We are not making explosives and have no need to discuss it further on the forum.

It would be a waste of chemicals to attempt to make your nitric acid stronger than 68%.
Actually, it is better to make it a bit more diluted and use heat in your processes.

I suggest using the cold nitric acid recipe so popular on the forum, removing the salts, then distilling the acids...

You do need to study, I can answer a question, or even a few thousand, but it would be very hard to even cover a tiny bit of the information that I have studied or experienced with concerning nitric acid, a thousand answer would not get you far in your research on this subject.

Take another breath,
Ok, let us get back to making nitric acid, learning from each other, and sharing what we work so passionately to find the answers too.


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## Mmbullion1776 (Jun 4, 2019)

butcher said:


> Take a breath, but do not breath those RED fumes, Re-LAx.
> 
> You can make fuming nitric acid, and distill 98% nitric.
> We are not making explosives and have no need to discuss it further on the forum.
> ...



Thanks so much I’m going to do some more research, and try to get a better understanding of the processes that are popular on here. Just so everyone knows I am using a full facemask by 3M rated for nitric acid.


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## g_axelsson (Jun 4, 2019)

Butcher is spot on. Too concentrated starting products. You need more water in your boiling flask.

Without water you are trying to condense NOx gases, there is no water to form the acid. Even stronger acid than 68% still needs some water and 98% sulfuric isn't going to let any of those 2% water it got get away. That strength of sulfuric is used to DRY other chemicals.

With a look at the chemical formulas of nitrate + sulfuric acid => sulfates + nitric acid you could find the perfect mix, but I'm very confident that it will be close to the amounts used in the cold nitric acid method found here at the forum. I would start with those proportions and take it from there.
Even better if you make the cold nitric first, then you don't have the problem with a solid chunk of sulfate salt in your boiling flask.

Fuming nitric acid has no use in refining and recovery, it was used as an oxidizer for rocket fuel and would self-ignite if it gets into contact with anything combustible. I've seen some instruction films from NASA where they were handling red fuming nitric acid and it was a bit scary how aggressive that chemical is.

Play it safe, dilute the starting product. If there is a lot of red fumes getting past the condenser then dilute it some more. Sunlight will break down the acid too and release some fumes so you might want to put some foils to block direct sunlight.

And don't get mad if some poster writes something you don't find helpful. It is often written in good faith, trying to warn you about dangers. We don't want people to get hurt. We have a number of members that have hurt themselves pretty bad, spending months hospitalized from doing what we do.

So thread carefully and don't be too offended when someone tries to help. Good luck with your studies. And when you got the distillation working, come back and share. We all love reading success stories.  

Göran


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## rickzeien (Jun 5, 2019)

This is a great thread. Someone willing to ask for advise and more experienced members willing to share their experience. The learning experience doesn't get any better than. 

Questions I never thought to ask and answers that I never knew I could find. 

Thanks to all who have contributed.

Sent from my SM-G950U using Tapatalk


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## Williamjf77 (Sep 12, 2019)

Dougs lab has a good video about this method, in my opinion the best and he explains all the reasons to start with nitrate, sulphuric and water.

I’ve done it several times, takes a while. Watch out for suck back from your fume scrubber at the end, that will end up in your product if you don’t take care. 

It happens very fast. You need a suck back trap or another way to vent the apparatus.


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## Williamjf77 (Sep 12, 2019)

Also I should add that thermometer still head is a bad idea for nitric acid, I had one blow out on me the first time I distilled nitric. Luckily it was mostly water vapors. I’m not a pro here but I can share my mistakes. Get thermocouples a thermocouple display and a thermocouple well that doesn’t put the probe in contact with the chemicals and a regular still head with ground joints. They are all so cheap now a days anyway and you get a digital read out. Probably <20$ shipped and you don’t have to worry about a thread on connection and that flimsy gasket for the thermometer. If you have to use that style wrap Teflon tape around the thermometer to get a good seal where you need it.

Also as everyone said red fuming nitric is nasty stuff, will set gloves on fire on contact and you have to store it completely different. I haven’t tried the cold nitric yet but that’s what I will do next, you can make way more for the amount of set up and clean up involved and then just distill the liquid if you find it necessary.


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## Beerocker1 (May 13, 2022)

Mmbullion1776 said:


> I’m running a simple distillation apparatus 1000ml round bottom flask, with Liebig condenser. I have 400grams of 98% potassium nitrate and 400 grams of 98% sulfuric acid in the flask reacting over heat. My thermometer says about 170f. I know that’s not exactly as hot as it should be. The problem is the reaction seems to be going fine but the cloud of nitric gas is just hovering around the condenser not going down it turning into liquid. The water running through it is ice cold I don’t know what the problem is.


I use sodium nitrate and distill as you suggest. My distillation works best at about 100°C. At that temp I still wrath my upper apparatus with aluminum foil and at that temp I get a nice steady drip. Nothing too fast, but a steady drip every 2 seconds or so


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## Beerocker1 (May 13, 2022)

Beerocker1 said:


> I use sodium nitrate and distill as you suggest. My distillation works best at about 100°C. At that temp I still wrath my upper apparatus with aluminum foil and at that temp I get a nice steady drip.  Nothing too fast, but a steady drip every 2 seconds or so


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## Jimbriese (May 13, 2022)

butcher said:


> There is no need to make fuming nitric acid it has no use at all in refining.
> 
> When water or a less concentrated sulfuric acid is used you will have water involved in the boiling reaction, this water will vaporize along with the decomposing nitrates which form the NOx gases and they will then combine and condense back into nitric acid when cooled in the condenser.
> 
> ...


You said it has no use in refining is that because it will cause issues with the processes or just because it has a more Violent reaction? 
I make my own nitric acid due to cost my first batch I made was with lab grade like he was use if here but those chems are sitting now I buy what I need at lowes. I get the Spectracide stump remover that is potassium nitrate and Zep sulfuric acid drain opener which I don’t know the Concentration of and it still makes a fuming nitric. 
Now my first time making nitric with the 98% sulfuric acid there was a lot more of the red fumes but as the temp got above 80c the fumes slowed down and it started to condensate into the receiver. Using the drain opener I get a lot less fumes but still end up with a fuming nitric acid. 
The only issue I have seen using this is it is very easy to add too much and get a boil over but I now cover whatever I’m processing with water then add nitric. Which slows down the reaction. 

Thanks in advance as yes I’m still new to this been researching this for few years just recently found this forum and it has been a life saver as trying to find info else where there is so much conflicting info out there it’s hard to distinguish between good and bad info. 
Been doing some small recovery and refining of gold and silver for a few months now trying to learn. 
I have about 2g of gold powder and a 2g bead of silver and hoping to add to them soon


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## butcher (May 13, 2022)

There are many reasons, too many to list here why fuming nitric acid is not needed and would be detrimental to good success in the processes of recovery or refining of metals

Many of the metals you are trying to dissolve with nitric will passivate (build an oxide coating that protects the metal from the acid) so the metal will not dissolve in a concentrated nitric but would dissolve more easily in a more dilute nitric solution.

Most metals that are dissolved in nitric, form nitrate salts which are soluble in water, in a diluted nitric solution you can hold more of these salts dissolved, so you can dissolve more metal in a dilute nitric than you can in a concentrated nitric without water which has no place for salts to remain in the solution.

The dangers of fires such as spills on wood tables, cotton, or organics materials become more of a concern, the loss of nitric due to fuming of copious amounts of NOx gassing which does no work in the reaction, no water to dissolve nitrates basically wasting the availability of the nitric to do the most work with less waste.

68% HNO3 azeotropic solution of nitric is the strongest we need to make aqua regia to dissolve gold or many of the platinum group metals, for silver we need much more water so we normally dilute the 68% nitric with equal volumes of water or more, to get the best reaction with silver and be able to keep the silver salts in solution...


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## Jimbriese (May 13, 2022)

Thanks for that I will start making it at a lower concentration.


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## Yggdrasil (May 14, 2022)

If you make it the way described it will be Azeotropic 68%.
No matter what you do it will never get stronger.
If you are aiming for stronger, pressure is needed, much more complicated.


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## Geo (May 14, 2022)

You are losing nitric acid to thermal decomposition. Nitric acid boils at 181°F. NO3 is colorless and produces nitric acid through distillation. NO2 has to be bubbled through water to produce nitric acid. If the reaction is too hot, the NO3 decomposes to NO2. What temp is the reaction when it's producing red NO2?


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## Geo (May 14, 2022)

My comment above was edited to add boiling point of nitric acid.
Potassium nitrate and sulfuric acid will produce nitric acid with no extra water producing nearly pure 98% white fuming nitric acid. The resulting solid cake left behind is potassium sulfate and is a real pain to remove from the boiling flask. It has to be dissolved with boiling water and potassium sulfate is mildly soluble in water.


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## butcher (May 14, 2022)

Dilute nitric acid will dissolve more metals into the solution.

The more added water or the more dilute your acid is, the more metals it will dissolve and the less of your acid will be wasted forming gases that escape the reaction.

The water will not only hold more dissolved nitrate salts, but the water will hold or dissolve the red NO2 gases from the reaction (the water basically reforms nitric acid by absorbing and reacting with the NO2 gas).

Dilution can also help to slow down the reactions which can also help it to run cooler with less heat generated the gases stay in solution longer (to react if they are able to. 

The clear NO portion of the NOx gas is not water-soluble and would be lost in this more dilute reaction.

Yes, it is a two-edged sword, the more diluted the slower the reaction will be.
As normal, it is good policy to use heat and concentration towards the end of the reaction when it slows towards a stop to drive the reactions to completion, to get full use of our nitric on metals like silver...

Adding some oxygen in the form of hydrogen peroxide (3% which is mostly water anyway would be fine) can help to make the nitric acid go further as the oxygen in the solution reacts with the clear NO gas to form red NO2 gas which is water-soluble and basically makes more nitric acid in solution from the water and hydronium ions in solution which can dissolve more silver or whatever metals your making or converting into soluble nitrate salts which dissolve in the acidic water of the solution


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## Jimbriese (May 15, 2022)

Ok so If I use the recipe I have 
80g potassium nitrate 
60ml sulfuric 90%
If I was to add 40ml of water to the boiling flask it should distill at about 60-65 % if I’m understanding what you said correctly? 

I watch the Doug’s lab videos that someone mentioned he is using a different salt and I will be looking for those as it looks to be a lot better as you don’t have the solid mass to deal with after completing. But right now I have about 10 lbs of potassium nitrate to use.


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## butcher (May 15, 2022)

Jimbriese,
Look into making poor man's nitric acid solution, it can be used as-is on many base metals or reactions where some sulfate will not cause problems with the reactions.


Poor mans nitric which is a good recipe for the reaction to get 68% HNO3 which can then be distilled for use with silver or for making aqua regia, by making poor-mans nitric acid and freezing the solution which helps you to remove the bulk of sulfate salts (that become a problem during the distilling process) is very helpful before trying to distill the solution, by removing the bulk of sulfate salts that form from the reaction before distilling the solution will put you much further ahead as you will not have many of the insoluble salts to deal with during the distillation process.

I prefer sodium nitrate salts over potassium nitrate salts their solubility makes it easier to deal with their sulfate compounds when making nitric acid.

Before attempting to distill, spend time understanding how to perform it safely, simple things like lowering the temperature on a reaction can cause a vacuum in a pressurized vessel, this vacuum can suck back cold liquid into the boiling hot glass flask of hot acids, shattering the glass and splashing and spraying hot acids all over you, and your laboratory...


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## Shark (May 15, 2022)

Butcher is right. I know because I learned those exact methods from him several years ago to make nitric acid. I still use them pretty often even now when I need nitric and run out. With some care it can be used on some metals by just mixing the right amounts in hot water with your metal. It seems an enormous task when first starting out but will get easier with time and study.


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## olawlor (May 16, 2022)

My standard operating procedure for nitric:

1L round-bottom flask
340g NaNO3 sodium nitrate prills
200g H2O
210g H2SO4 concentrated sulfuric acid

Add powder funnel to round bottom flask. Place flask in ring on scale. Add one quartz boiling chip to flask, note mass, and tare scale. Add prills first, liquid, and then sulfuric. Immediately transfer round bottom to heating mantle and seal glassware. Dial in heating mantle for 118C vapor temperature. Add aluminum foil reflectors around flask and thermometer adapter. Liquid should come over clear. Boil until bubbles get small, usually under an hour. Do NOT leave it unattended.

Let cool to 80C, carefully add 10mL of cold water to the boiling flask to keep the salts from crystallizing. Pour out sodium hydrogen sulfate leftovers before they cool (and solidify).

Yield: about 250mL of about 40-50% nitric acid (a perfect concentration for dissolving silver or base metals).

Hazards: without sufficient water in the flask, red Nitrogen Dioxide fumes will be emitted during distillation. These are POISONOUS: the nitrogen dioxide LC50 for inhalation is below 200ppm, more toxic than cyanide gas. (You can die up to several weeks later, the gas having burned the inside of your lungs.) SEVERE FIRE HAZARD: hot nitrogen dioxide gas will cause rubber O-rings to emit flames and smoke.

Hazard mitigation: Work in a fume hood with negative pressure. Use secondary containment, since none of these materials are OK to spill on anything except glass. Stop heating while there is still visible liquid in the boiling flask. Do not allow the vapor temperature to exceed 130C. If red gas is escaping apparatus, vacate the area immediately and turn off heating remotely.


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## Jimbriese (May 16, 2022)

Thank everyone for advice.


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## Geo (May 16, 2022)

Calcium nitrate, water and sulfuric acid produces nitric acid at 68% right from the reaction. The resulting cake will be calcium sulfate (gypsum) and is much easier to remove from your glassware. I can get the amounts and temp. It's in my notes. I'll have to dig it out.


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