RogueRose
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Refluxing Calcium nitrate (with some NH4NO3) with Ca(OH)2 - how long should this take?
I've found that there is significant amounts of NH4NO3 in my Ca(NO3)2 and I wanted pure calcium nitrate so I decided to boil a solution with excess
Ca(OH)2 and it is putting out A LOT of NH3. The boiling action seems to be mixing the hydroxide pretty well and it's at a rolling boil and I have a
mix of steam and NH3 coming over to a frozen HCl mixture that is working nicely. I'm wondering how long this reaction should need to run or if the
conversion is done pretty quickly. I'm working with about 4 moles of cal nitrate and I used 100g of cal hydroxide (about 1.2 L of solution).
I'm thinking that the reaction happens pretty quickly as I could tell it was working as soon as the hydroxide was added to the room temp solution.
As for removing the NH3 from the solution of Ca(NO3)2 once the remaining hydroxide is filtered out, I guess the only option is to boil it off or slow
evaporation (which is difficult with Ca(NO3)2 b/c it's so hygroscopic). I'd like to have as much NH3 removed from the solution before I try to dry it
in an oven and I'm wondering how much ammonia a boiling solution can hold. Also, is there any other method that I may be overlooking? I guess I
could put it under vacuum but I really didn't want to mess with that, but if it will make a big difference, I might have to give it a shot.
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Syn the Sizer
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I can't say how long the process will take, but as for removal of NH4OH in solution, I would do a slow boil until I no longer smell
NH3 coming out of solution.
Are you bubbling it through HCl to produce NH4Cl as a 2nd reaction?
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Tsjerk
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I just dried a reaction of a chloride with sulfuric acid to evaporate the HCl of and obtain the sulfate, and found I had to boil the solution down to
about ten percent twice before I got rid of the last chloride.
After the first time boiling to almost dryness there was a strong hydrochloric smell persisting. So maybe you will have to add water once or twice to
get rid of the last ammonia, although ammonia should be less hard to get rid of compared to HCl.
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RogueRose
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Quote: Originally posted by Syn the Sizer  | I can't say how long the process will take, but as for removal of NH4OH in solution, I would do a slow boil until I no longer smell
NH3 coming out of solution.
Are you bubbling it through HCl to produce NH4Cl as a 2nd reaction? |
Yes, I put some HCl in b/c my solution was getting too hot and wasn't catching all the NH3 coming over, so I figured if I added some HCl, it would
grab any free ammonia pretty quick even if it got warm (this was all on my first run). On the second run, I chilled it all first to a frozen slush and
it worked really well.
I'm still looking for a chart that tells max NH3 concentration by temp, and I suspect it drops pretty low when under vacuum (and high heat).
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Syn the Sizer
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Ok, I bubble it through water or HCl depending if I want ammonium or ammonium chloride. I usually just go with water since I have more uses for
ammonium. I also found that if my ammonia came over too fast it would propel NH4Cl gas into the air so I had to be more watchful of the
reaction.
You probably already have this covered, but make sure you have a trap between the reaction vessel and the HCl bubbler, The first time I was boiling
cleaning ammonia to collect the vapours, I didn't use a trap, I removed the foil from my reaction flask to look at the solution and see how it was
boiling and within seconds all the solution sucked back. !.5hrs wasted.
With my situation it wasn't too bad it was just concentrated ammonium into cleaning ammonia and I just needed to start over and recollect the gas.
with yours would have a hard to separate mixture.
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Refinery
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I made ammonia solution with urea, NaOH and water and it took a good two hours until the bubble evolution slowed down to warrant finishing.
Considering the Ca hydroxide is in insoluble state, it has significantly lower reaction rate and that could explain the long refluxing time.
I ran my ammonia infusion at full speed, and the bubbler was going all over wild, but the ammonia flask held in cold water bath easily absorbed all
the ammonia, and the continuous flow of gas just disappeared at the end of the gas tube into the water, zero gas raising through the water. Suckback
is a real issue and it will happen if you don't use check valve, middle flask or just disengage the tube right when you stop heating the reaction. I
almost got a suckback and was lucky enough to deplug the tube just in time.
When I was younger, I cracked a flask filled with NaCl and Na bisulfate when I was making HCl. The heat required for the process is so high the bottom
of the flask just fell right off when the suckback happened and I had to evacuate myself due to HCl emission. Learned a lesson, paid 40 bucks for the
flask, 5 bucks for the reagents + 4 hours of my time, and got a rusty, HCl-etched hotplate as a trophy.
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Syn the Sizer
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Suck back can even happen with heat on when the temp drops for whatever reason. In my case, I was outside and there was a breeze, I had a crappy
hotplate that didn't heat well. It cooled the flask quickly as took the foil off the flask. I was looking at the solution in the flask and didn't
notice the suck back starting, before I had a chance to pull the tube out it was all in the reaction flask. After that I always used a middle catch
that was at least double the volume of what I am bubbling into.
With me though it was just ammonia solution into cleaning ammonia solution so no quantity of vapours escaped, and my flask was fine. That would be
aggravating though to have what happened to you happen, not only did you lose your reagents and flask but your hours of time too.
[Edited on 20-7-2020 by Syn the Sizer]
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RogueRose
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| Quote: Originally posted by Tsjerk | I just dried a reaction of a chloride with sulfuric acid to evaporate the HCl of and obtain the sulfate, and found I had to boil the solution down to
about ten percent twice before I got rid of the last chloride.
After the first time boiling to almost dryness there was a strong hydrochloric smell persisting. So maybe you will have to add water once or twice to
get rid of the last ammonia, although ammonia should be less hard to get rid of compared to HCl. |
I suspect that as well since NH3 has a much lower BP IIRC. I might just put the hot plate outside and just not worry about dealing with the NH3. The
only thing I'm wondering is if the NH3 is going to react with the Ca(NO3) and move back to making NH4NO3 as I dry it. I thought Ca(OH)2 is the
stronger base but thought I remembered some strange things happening at times when NH3 is in solution.
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RogueRose
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| Quote: Originally posted by Syn the Sizer | Ok, I bubble it through water or HCl depending if I want ammonium or ammonium chloride. I usually just go with water since I have more uses for
ammonium. I also found that if my ammonia came over too fast it would propel NH4Cl gas into the air so I had to be more watchful of the
reaction.
You probably already have this covered, but make sure you have a trap between the reaction vessel and the HCl bubbler, The first time I was boiling
cleaning ammonia to collect the vapours, I didn't use a trap, I removed the foil from my reaction flask to look at the solution and see how it was
boiling and within seconds all the solution sucked back. !.5hrs wasted.
With my situation it wasn't too bad it was just concentrated ammonium into cleaning ammonia and I just needed to start over and recollect the gas.
with yours would have a hard to separate mixture. |
Lol, man I wish this post had been made about 30 mins before,  I turned the hot
plate off and forgot to take the funnel out of the bubbler mix and I came back to 500ml having sucked back into the nitrate mix. G-D it!! Oh, well,
I'll use this as fertilizer and start over. The problem is that I have to filter the mix first b/c there is some "scum" (similar to very fine clay)
that rises to the top when I dissolve the Ca(NO3)2. I have to make a vacuum setup with a bottle in between to keep this from happening again.. The
last time this happened to me was when I was trying to make a concentrated NH3 solution as well.
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RogueRose
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| Quote: Originally posted by Syn the Sizer | Suck back can even happen with heat on when the temp drops for whatever reason. In my case, I was outside and there was a breeze, I had a crappy
hotplate that didn't heat well. It cooled the flask quickly as took the foil off the flask. I was looking at the solution in the flask and didn't
notice the suck back starting, before I had a chance to pull the tube out it was all in the reaction flask. After that I always used a middle catch
that was at least double the volume of what I am bubbling into.
With me though it was just ammonia solution into cleaning ammonia solution so no quantity of vapours escaped, and my flask was fine. That would be
aggravating though to have what happened to you happen, not only did you lose your reagents and flask but your hours of time too.
[Edited on 20-7-2020 by Syn the Sizer] |
I'm wondering how using either a ceramic blanket or a sheet of fiberglass insulation would work in place of the foil (or in addition?). I guess I
need to figure out a setup to to eliminate or reduce the chances of this issue.
just out of curiosity is suck back more likely if distilling under vacuum?
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Syn the Sizer
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Crap, that sucks, but to be honest, I am sure almost everybody here has had suck back ruin product at least once. I know I have seen it happen on
YouTube to a couple YouTubers. Take it as a learning experience. The best fail safe is a middle bottle used as a trap to catch the suck back and if
you wish an inverted funnel too, though I never use one. Also ammonia is quite hygroscopic and will draw water up the tube on its own, but as long as
your are producing gas it usually stays in the bottom of the tube.
Ceramic blanket could help, it would retain heat longer than foil, and possibly slow down the start of suck back. As for the vacuum question, I am not
certain if it would prevent suck back, but in theory is should help prevent it or at least slow it down. It would produce a vacuum on the receiving
flask side and if it is stronger than the vacuum produced on the reaction flask side it might. But you will want to break the vacuum before shutting
off the pump or you might still risk suck back.
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RogueRose
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| Quote: Originally posted by Syn the Sizer | Crap, that sucks, but to be honest, I am sure almost everybody here has had suck back ruin product at least once. I know I have seen it happen on
YouTube to a couple YouTubers. Take it as a learning experience. The best fail safe is a middle bottle used as a trap to catch the suck back and if
you wish an inverted funnel too, though I never use one. Also ammonia is quite hygroscopic and will draw water up the tube on its own, but as long as
your are producing gas it usually stays in the bottom of the tube.
Ceramic blanket could help, it would retain heat longer than foil, and possibly slow down the start of suck back. As for the vacuum question, I am not
certain if it would prevent suck back, but in theory is should help prevent it or at least slow it down. It would produce a vacuum on the receiving
flask side and if it is stronger than the vacuum produced on the reaction flask side it might. But you will want to break the vacuum before shutting
off the pump or you might still risk suck back. |
The dumb thing is that I'm well aware of it, I just got distracted after turning the heat off and next thing I know I had this sinking feeling like
"oh shit, is it too late", and yup it was.
I'm looking into some check valves as that will allow only one way flow. I find it kind of odd that I don't see more people talk about this. They
are actually pretty easy to make as well and if you don't need a lot of flow volume (like liters per minute), then something like a 1/4 -3/8" should
be fine. I'm going to make a few, the only problem is working with materials that won't be effected by chemicals coming over. I think using ceramic
ball bearings might work well or even marbles. The hardest part might be some kind of O-ring, as IDK of a highly resistant material that is also
squishy but maybe PTFE will work - any suggestions on materials welcome!
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Syn the Sizer
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Yes, I honestly should use check valves it is a very effective method. As for materials to use, that is a good question. I will do some thinking and
if I can come up with anything I will post it.
PTFE is great stuff but it's so rigid, I wonder if there is a type of fluorinated rubber with more give.
[Edited on 21-7-2020 by Syn the Sizer]
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Syn the Sizer
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I just thought, a viton seal is a fluorinated rubber. you could fashion one with PTFE tubing a viton seal and a ceramic bearing. You could use PTFE
tubing of 2 different diameters, one with an OD small enough to fit into the larger one. mount a viton seal inside the larger tube on the smaller
tube, drop the bearing in and install another smaller PTFE tube with a couple notches to prevent accidental sealing, chances are it won't happen with
PTFE tubing but you never know. there we go a chemically resistant check valve.
[Edited on 21-7-2020 by Syn the Sizer]
[Edited on 21-7-2020 by Syn the Sizer]
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Fyndium
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I think teflon is a bit overkill for most uses. Last time I checked normal polyethene works with almost every chemical unless you are boiling them.
For gassing room temp vapors it should work very fine.
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AJKOER
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If your goal is to separate out the NH4NO3 from the Ca(NO3)2 mix, per a source:
"The thermal decomposition of calcium nitrate to produce calcium oxide, nitrogen dioxide and water. This reaction takes place at a temperature of over
600°C."
Source: https://chemiday.com/en/reaction/3-1-0-3910
Where as:
"The thermal decomposition of ammonium nitrate to produce dinitrogen monoxide and water. This reaction takes place at a temperature of 200-260°C."
Source: https://chemiday.com/en/reaction/3-1-0-32
So, consider as an option to be tested in small amount, a simple efficient clean unmessy process which is just place it in a heated pan (at over 200 C
and well spread out in a thin layer) to effect mild heating of the mix in an open pan. Then dissolve in distilled water to separate out the CaO from
the Ca(NO3)2.
Avoid strong rapid heating (unsafe) or heating in a closed vessel or otherwise working with the dry mix in the presence of metal impurities (like
copper ions). Per an MSDS (see https://fscimage.fishersci.com/msds/04020.htm) on Ca(NO3)2 to quote:
"Incompatibilities with Other Materials: Strong reducing agents, ammonia, finely powdered metals, hydrazine, organic materials, combustible
materials."
The action of heating on Calcium nitrate hydrate forms H2O and possibly also some HNO3 and NH3 (from NH4NO3 at 170 C, see https://www.nature.com/articles/1731188a0). The ammonia and water presence could lead also to Ca(OH)2 and perhaps more ammonia (from OH- acting on
NH4+), so expect some product loss (which would be determined from the small scale testing).
[Edited on 21-7-2020 by AJKOER]
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Syn the Sizer
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| Quote: Originally posted by Fyndium | | I think teflon is a bit overkill for most uses. Last time I checked normal polyethene works with almost every chemical unless you are boiling them.
For gassing room temp vapors it should work very fine. |
Yes, polyethene works great but if you were making a check valve that you wanted to keep using PTFE is better, I am assuming RogueRose would be using
the check valves for everything including possibly nitric acid distillation so I think PTFE will be better and have lasting power.
You would still use polyethylene tubing on either side of the check valve if not distilling something which needs PTFE but the valve need to last
several uses so as not to be a waste of time to make.
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RogueRose
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| Quote: Originally posted by Fyndium | | I think teflon is a bit overkill for most uses. Last time I checked normal polyethene works with almost every chemical unless you are boiling them.
For gassing room temp vapors it should work very fine. |
I agree but I was thinking about distillation of acids - mainly HNO3, HCl and SO2/3 which would be the main and most common acids distilled (which
works even better under vacuum obviously). I only brought this up b/c if it is possible to make them resistant to those compounds on the first try,
it might be worth it.
I did find some fluorinated O-rings and it seems there are a number of flexible fluoro compounds that can do the job. The first thing I found was a
pair of fluorinated gloves that look like standard dish gloves, but almost $400! Wow!!
https://www.phelpsgaskets.com/blog/how-to-chose-o-ring-mater...
https://o-ring.info/en/materials/vitonr--fkm/
It looks like the compound "Viton" (FKM or FPM) is one that is available.
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RogueRose
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| Quote: Originally posted by Syn the Sizer | I just thought, a viton seal is a fluorinated rubber. you could fashion one with PTFE tubing a viton seal and a ceramic bearing. You could use PTFE
tubing of 2 different diameters, one with an OD small enough to fit into the larger one. mount a viton seal inside the larger tube on the smaller
tube, drop the bearing in and install another smaller PTFE tube with a couple notches to prevent accidental sealing, chances are it won't happen with
PTFE tubing but you never know. there we go a chemically resistant check valve.
[Edited on 21-7-2020 by Syn the Sizer]
[Edited on 21-7-2020 by Syn the Sizer] |
I like what you are thinking. I'm wondering if glass can be used in place of some of the PTFE tubing? It would be much easier to find and maybe it
would be worth a try to get the idea down - maybe even use a glass marble with a viton o-ring.?
I've seen some check valves that use gravity or flow rate/pressure as well as spring actuated valves. I'm thinking if suck back happens will there be
enough pressure to move a ball (glass or ceramic) against the O-ring? I think the faster the suck back happens, the better the valve will work.
If you can think of any kind of spring, I'd be interested, otherwise I think I might look at making the valve "positional" meaning it will have to be
vertical with the return/suck back direction towards the bottom so it can use gravity as the spring and to keep it in the "off" or blocked position by
default.
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Syn the Sizer
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| Quote: Originally posted by RogueRose | | Quote: Originally posted by Syn the Sizer | I just thought, a viton seal is a fluorinated rubber. you could fashion one with PTFE tubing a viton seal and a ceramic bearing. You could use PTFE
tubing of 2 different diameters, one with an OD small enough to fit into the larger one. mount a viton seal inside the larger tube on the smaller
tube, drop the bearing in and install another smaller PTFE tube with a couple notches to prevent accidental sealing, chances are it won't happen with
PTFE tubing but you never know. there we go a chemically resistant check valve.
[Edited on 21-7-2020 by Syn the Sizer]
[Edited on 21-7-2020 by Syn the Sizer] |
I like what you are thinking. I'm wondering if glass can be used in place of some of the PTFE tubing? It would be much easier to find and maybe it
would be worth a try to get the idea down - maybe even use a glass marble with a viton o-ring.?
I've seen some check valves that use gravity or flow rate/pressure as well as spring actuated valves. I'm thinking if suck back happens will there be
enough pressure to move a ball (glass or ceramic) against the O-ring? I think the faster the suck back happens, the better the valve will work.
If you can think of any kind of spring, I'd be interested, otherwise I think I might look at making the valve "positional" meaning it will have to be
vertical with the return/suck back direction towards the bottom so it can use gravity as the spring and to keep it in the "off" or blocked position by
default. |
I definitely think glass tubing will work, in fact it might be easier, to seal f it is all glass since you can melt the glass together with a torch.
Your positional idea was what I was thinking when you mentioned the concern of sealing, have it in a normally closed position. I wonder if there is a
flexible PTFE spring that could be used to keep pressure on the ball.
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Syn the Sizer
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This site sells all sorts of Kyflon (FFKM), a perfluoropolymer which is what viton seals are made of. You might find some useful stuff on the site
http://www.highperformanceseal.com/?gclid=Cj0KCQjwpNr4BRDYAR...
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