negative pressure in reaction vessel

[TomVader]

Hello everyone, I'm new to all this and would like your input on a strange result. I attempted to make nitric acid by bubbling NOx through a 3% solution of H2O2. I did it just like the Nurdrage video on UTube. My gas generator was a 1000ml filter flask with a stopper in the top and a short length of PVC tubing from the side arm. A bent glass tube ran from the PVC into a 100ml volumetric flask. In the 1000ml flask I put 80g potassium nitrate (stump remover), 50ml water, 32g clean copper wire and 100ml HCl at 31% concentration. In the 100ml flask I put 25ml H2O2 at 3% concentration. The 100ml flask sat in an ice water bath. I know the video recommended H2O2 at 30% concentration but it said using plain water would work but the result would be a weaker acid. The reaction progressed just like in the video for about 15 minutes and then instead of continuing to bubble, the H2O2/nitric started getting sucked up into the glass tube. At first just a little bit and then it would be forced down and make a bubble and then get sucked up again. After about 15 more minutes it was getting sucked up almost to the top of the flask! I don't know how this was possible as the reaction was still going on and (supposedly) still producing gasses. The end result was a very weak nitric acid. Any thoughts? Thank you all in advance for your answers and for your excellent forum.

 

[grance]

HHmmm thats how I make it. I use 99% potassium nitrate 110g, 35g copperwire and 150ml of 33% Hcl. It is weak but works and I also use 3% h202. The only other diffrence is I use a 500ml filter flask and a 50ml glass graduated cylinder.

 

[butcher]

TomVader,
Steam boilers or pressure vessels in the early days were used more for vacuum than they were for pressure, they use to use boilers to pump or suck water out of the ground using the vacuum they created as the vessel cooled.

At first the reaction builds its own heat and pressure forcing the NOx gas out of solution, but as the reaction slowed or temperature was lowered it created a vacuum and sucked back your solution into the reaction vessel.

this can be very dangerous when distilling, as if the cold liquid sucks back into the boiling flask with hot acids the cold liquid can burst the boiling vessel with hot acids all over you.

Keep the boiling vessel hot, do not lower temperature or pressure (without removing hose to the cold liquid).
If lowering temperature or pressure, disconnect output hose or fitting and allow vessel to suck air as it cools.
Also the boiling points for nitric acid change with the acids concentration,

I have a process that makes nitric acid and de-plates gold foils from copper plated pins at the same time, it also make copper sulfate as a byproduct, in my explanation I describe the distilling process and give some safety information on using it I think you could find it helpful,

I called it killing two bird with one rock, I will try to find links and edit this to add them.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=38&t=6199&hilit=killing+two+birds+one+rock
there were others of these similar.

 

[TomVader]

It seems obvious now (now that someone explained it to me!). The reaction was still going on and producing NOx, but since it was also cooling off at the same time it created a vacuum. So adding heat at this point would have kept the pressure higher in the reaction vessel forcing the gasses into the reciever and resulting in a higher concentration nitric acid instead of the pitifully weak product I ended up with. Thank You very much. I'll be trying this again on a small scale until I get a satisfactory product, provided I can find more stump remover made with potassium nitrate. The can I used has been sitting around in a cupboard for 10+ years. I recently tried to find more at one of the Big Box stores and they told me that they no longer carry it because "...the chemicals in it were deemed to be too dangerous." They didn't even carry the meta bisulfate variety! Thank you again Butcher!

 

[BJL1984]

does anyone know, what the gram amount of ammonium nitrate would be, as i have a bunch of it left over from this years landscaping adventures I would like to use it up so its not sitting around my garage all winter, I have had much success doing this reaction with sodium, and potassium nitrate just want to ba able to utilize the chemicals i have around with out buying more

 

[butcher]

100ml H2O boiling
202g potassium nitrate KNO3
OR
170g sodium nitrate NaNO3
Dissolve in the boiling water above cool.
Add slowly little at a time 56ml 98% sulfuric acid H2SO4.
Potassium salts can hold HNO3 if cooled too fast, slowly cool solution, put solution in freezer to chill solution (loose fitting lid so jar can adjust or breath off pressure or vacuum).
Decant solution from crystals, yield about 160ml of approximately 50% HNO3.

This is Laser Steve’s poor mans nitric acid formula, and is the best recipe I have found for refining.

For a six times formula:
This will fit a Mr. Coffee Pyrex coffee pot on a solid burner hot plate.
600ml H2O
1212g KNO3
Or
1020g NaNO3
336ml 98% H2SO4
2 spoons 30% H2O2
Yield approximately a quart of 50% HNO3

Distill the home made nitric acid if using it for silver to leave sulfate salts in boiling flask and retrieve nitric in receiver (sulfates cause problems with silver).

Two moles of sodium nitrate and sulfuric acid produce 2 moles of nitric acid solution and sodium sulfate:
2NaNO3 + H2SO4 = 2HNO3 + Na2SO4


Ammonium nitrate can make nitric acid but it can also make a dangerous explosive if not done properly.
With this in mind, I do not recommend using it to make nitric acid, the potassium or soduim nitrates are just as easy to get, and your not risking an explosion in their use.
so I will not give the formula.

When you make a chemical you use molecular weights and the formula of the reaction to determine how much reagents to use.

 

[BJL1984]

fair enough about the ammonia stuff, its probably a good thing I didnt go testing it, I'll just save it for the lawn, thanks for the info butcher

 

[mikeinkaty]

100ml H2O boiling
202g potassium nitrate KNO3
OR
170g sodium nitrate NaNO3
Dissolve in the boiling water above cool.
Add slowly little at a time 56ml 98% sulfuric acid H2SO4.
Potassium salts can hold HNO3 if cooled too fast, slowly cool solution, put solution in freezer to chill solution (loose fitting lid so jar can adjust or breath off pressure or vacuum).
Decant solution from crystals, yield about 160ml of approximately 50% HNO3.

This is Laser Steve’s poor mans nitric acid formula, and is the best recipe I have found for refining.

For a six times formula:
This will fit a Mr. Coffee Pyrex coffee pot on a solid burner hot plate.
600ml H2O
1212g KNO3
Or
1020g NaNO3
336ml 98% H2SO4
2 spoons 30% H2O2
Yield approximately a quart of 50% HNO3

Distill the home made nitric acid if using it for silver to leave sulfate salts in boiling flask and retrieve nitric in receiver (sulfates cause problems with silver).

Two moles of sodium nitrate and sulfuric acid produce 2 moles of nitric acid solution and sodium sulfate:
2NaNO3 + H2SO4 = 2HNO3 + Na2SO4


Ammonium nitrate can make nitric acid but it can also make a dangerous explosive if not done properly.
With this in mind, I do not recommend using it to make nitric acid, the potassium or soduim nitrates are just as easy to get, and your not risking an explosion in their use.
so I will not give the formula.

When you make a chemical you use molecular weights and the formula of the reaction to determine how much reagents to use.

Butcher - Since 3% h202 is readily available, would using 100 ml of 3% h2o2 and 500 ml of water work in the above method? And, what does the h2o2 do in the recipe? (2 tsp =~ 10 ml)

And, when you say 50% nitric, about what S.G. would this be? I'm thinking of Goldsilverpro's discussion on what you really get when you do a 50-50 mix of 68% Nitric Acid and water?

Mike

 

[kadriver]

In the 1000ml flask I put 80g potassium nitrate (stump remover),

Make sure you got the right "Stump Remover"

Stump Remover made by Spectricide is KNO3 (Potassium Nitrate)

Stump Remover by Bonide (Called "Stump Out") is Sodium Metabisulfite.

I have both of these chemicals in my inventory with MSDS sheets.

kadriver

 

[TomVader]

The brand name was "High Yield", label said "...contains potassium nitrate" It didn't say how pure it was. Lowe's doesn't carry stump remover anymore (not even the SMB type). They told me that the chemicals it contains were deemed to be too dangerous. So I got 99% pure off of Amazon.

 

[mikeinkaty]

In the 1000ml flask I put 80g potassium nitrate (stump remover),

Make sure you got the right "Stump Remover"

Stump Remover made by Spectricide is KNO3 (Potassium Nitrate)

Stump Remover by Bonide (Called "Stump Out") is Sodium Metabisulfite.

I have both of these chemicals in my inventory with MSDS sheets.

kadriver

Ace hardware here in Houston has "Stump-Out" by Bonide. Since the ingredints were not listed I called their 800 number. The guy there said it was SMB.