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Author: Subject: Picric acid: different instructions
B(a)P
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[*] posted on 14-12-2022 at 20:51


Quote: Originally posted by ManyInterests  
The picture is from my third batch. I will describe everything on what happened.

The synthesis went normal, but I used too much water and too much ice to crash the picric in, the result is I had almost no crystals filtered out. I decided to just boil everything down. Look up at the post where I have two pictures of my beaker, this is what I was describing. After filtering that stuff down, I boiled the stuff even more and I got what I thought was more picric, but it must have been REAL dirty since it was eating away at the paper filter.

I hated it so much that I neutralized it with sodium bicarbonate and just dumped the sodium picrate with large amounts of water down the drain. I hate having to do that, but this is not a good batch at all and I cannot mix it with anything else.

I hope my fourth batch doesn't suffer the same fate!


Ah I see, looks like you just tried to squeeze too much pout of that batch. What sort of yields are you getting? Once you are around 75% yield it is time to pull out.
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[*] posted on 14-12-2022 at 23:12


You cannot boil down the water in which you crashed your picric acid without also getting H2SO4 when you filter out your picric acid.
All the H2SO4 left from your nitration is still in there !

You say you are going to boil down 2100ml to 600ml. How much of this will be acid ? (All the acid you used)

Crash ---> Filter then do a recrystallization in distilled water.
This water you can boil and get a second crop.





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[*] posted on 15-12-2022 at 02:15


Great catch Herr Haber, I was thinking we were talking about the first recrystallisation.
IMHO you don't need to crash the nitration mix when undertaking a picric acid synthesis.
Once the reaction is complete chill the mix down in an ice bath, or fridge if you have it, and leave it for a good few hours.
Then, as Herr Haber says, filter and start the recrystallisation.
When you do recrystallise, add less water than you know you need, take the mixture to around 100 C then slowly add water a little at a time while keeping the temp up until everything is dissolved (noting that you might have some crap in their that will never dissolve). If your solution is free of solids leave it to cool, once it is room temperature chill it down further for a few hours at least, then filter. If your solution has a little insoluble crap in the bottom decant into another beaker and do as above.
You probably already know it, but best not to stockpile too much of it.......
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[*] posted on 15-12-2022 at 03:00


Is it better to crash it in ice cubes (as Rosco wrote) or just ice cold water? It's actually kinda hard to gauge how much ice I need, but if 'dump it in twice the volume of water' I can measure that far more easily. The water I add to the picric before dumping is also part of the water it will be crashed into. A slight excess is OK I suppose, just not a large one.

I am learning a lot. It seems that picric acid is different than other EM I worked with. I managed to make ETN, NHN, RDX, and I will be making PETN now that I have some pentaerythritol. Picric acid is different since the rest are insoluble in water and I can just repeatedly pour water over them in order to clean out the acid, with or without bicarbonate (though I should wash with a bit of bicarbonate I know)

I have a feeling that I might need to just destroy all the picric I made and start over from scratch. I would have used almost an entire liter of H2SO4 and hundreds of grams of nitrates, but I remember having to make nitric acid almost 5 times before I finally had a usable batch.

and I guess you must let the nitrated mixture cool to room temperature? I didn't let it cool that much. That is another thing I just learned now.

So I am going to list the steps needed to make good picric acid right now as a note for the future going forward. Because So far I would have made 7 batches of picric acid and I am thinking I need to dispose of what I have (sodium bicarbonate to turn into sodium picrate then pour the down the drain with large amounts of water) and start from scratch.

1: Do the synth. Let the ASA dissolve and stir in the H2SO4 for 2 hours or so at 120C.
2: Let cool to around 85C and add the nitrate salts slowly with lots of mixing. Try to maintain temperature around 95C not above 100C.
3: Heat with stirring to 120C and allow to stay there for at least 5 minutes
4: Cool to room temperature
5: Add ice cold water SLOWLY to the nitration mixture. If I am using 50 grams of ASA, this should be around 150ml to 200ml of water?
6: Crash in ice cold water, around 600ml to 700ml? Or maybe that much in ice cubes, I am still not decided.
7: Let settle for two hours, keep everything cold
8: filter the crystals
9: DISPOSE OF THE LEFTOVER LIQUID
10: Only recrystalize the stuff that is in the filters
11: After filtering out the liquid, and the crystals from that, I can boil that leftover liquid down for more crystals and only that?

Am I on the right track here?

Edit: I guess the main flaw is using too much water when crashing the stuff, resulting in very little crystals filtered out, hence me trying to get more by boiling the stuff down. I need to make sure I use only enough.

[Edited on 15-12-2022 by ManyInterests]
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[*] posted on 15-12-2022 at 03:23


Quote: Originally posted by ManyInterests  
Is it better to crash it in ice cubes (as Rosco wrote) or just ice cold water? It's actually kinda hard to gauge how much ice I need, but if 'dump it in twice the volume of water' I can measure that far more easily. The water I add to the picric before dumping is also part of the water it will be crashed into. A slight excess is OK I suppose, just not a large one.

I am learning a lot. It seems that picric acid is different than other EM I worked with. I managed to make ETN, NHN, RDX, and I will be making PETN now that I have some pentaerythritol. Picric acid is different since the rest are insoluble in water and I can just repeatedly pour water over them in order to clean out the acid, with or without bicarbonate (though I should wash with a bit of bicarbonate I know)

I have a feeling that I might need to just destroy all the picric I made and start over from scratch. I would have used almost an entire liter of H2SO4 and hundreds of grams of nitrates, but I remember having to make nitric acid almost 5 times before I finally had a usable batch.

and I guess you must let the nitrated mixture cool to room temperature? I didn't let it cool that much. That is another thing I just learned now.

So I am going to list the steps needed to make good picric acid right now as a note for the future going forward. Because So far I would have made 7 batches of picric acid and I am thinking I need to dispose of what I have (sodium bicarbonate to turn into sodium picrate then pour the down the drain with large amounts of water) and start from scratch.

1: Do the synth. Let the ASA dissolve and stir in the H2SO4 for 2 hours or so at 120C.
2: Let cool to around 85C and add the nitrate salts slowly with lots of mixing. Try to maintain temperature around 95C not above 100C.
3: Heat with stirring to 120C and allow to stay there for at least 5 minutes
4: Cool to room temperature
5: Add ice cold water SLOWLY to the nitration mixture. If I am using 50 grams of ASA, this should be around 150ml to 200ml of water?
6: Crash in ice cold water, around 600ml to 700ml? Or maybe that much in ice cubes, I am still not decided.
7: Let settle for two hours, keep everything cold
8: filter the crystals
9: DISPOSE OF THE LEFTOVER LIQUID
10: Only recrystalize the stuff that is in the filters
11: After filtering out the liquid, and the crystals from that, I can boil that leftover liquid down for more crystals and only that?

Am I on the right track here?

Edit: I guess the main flaw is using too much water when crashing the stuff, resulting in very little crystals filtered out, hence me trying to get more by boiling the stuff down. I need to make sure I use only enough.

[Edited on 15-12-2022 by ManyInterests]



Don't do step 6 and maybe omit step 5. After step 4 chill to 5 C for a few hours, if you have significant precipitate, filter and go to step 9. If nothing (or way less than expected) precipitates add the same mass of ice as your starting ASA mass. Chill to 5 C for a few hours and then filter. Go to step 9.
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[*] posted on 15-12-2022 at 03:34


OK so I will rewrite my steps again (for me to reference, and for posterity, for future picric acid makers).

1: Do the synth. Let the ASA dissolve and stir in the H2SO4 for 2 hours or so at 120C.
2: Let cool to around 85C and add the nitrate salts slowly with lots of mixing. Try to maintain temperature around 95C not above 100C.
3: Heat with stirring to 120C and allow to stay there for at least 5 minutes
4: Cool to room temp and then put in the fridge until it is 5C or so
5: Add the ice cold water to it slowly
6: Let it cool down AGAIN in the fridge
7: Filter the crystals
8: dispose of the left over liquid
9: recrystalize

I need to crush some ice in the blender. I was using large ice cubes. Not good since they take a while to melt... which is nice for drinks, but not good for picric acid.


Edit: Another question. While I have been using ASA so far and I will be for quite a while (I have two 500 pill bottles on standby). I know that you add 1.8 grams of sodium nitrate to 1 gram of ASA, I found some sources of pure salicylic acid. If I go that route, how much nitrate do I need to add? Same or a little less or more?

[Edited on 15-12-2022 by ManyInterests]
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[*] posted on 15-12-2022 at 08:59


Quote: Originally posted by B(a)P  

IMHO you don't need to crash the nitration mix when undertaking a picric acid synthesis.

Oh but it really is ! Usually adding a bit of water to the beaker is enough.
Crashing, as in pouring that beaker in a large amount of water is overkill though.
Picric acid is more soluble in concentrated H2SO4 than it is in water. I have the number 70 in my head for some reason. That's probably the threshold at which H2SO4 is a better solvent than water for picric acid.
And since the spent acids should be around 80% H2SO4 and the rest being water and a fraction of a % of HNO3 adding a bit of water will crash the picric acid out of solution.
Up to the point of course that adding too much water will also dissolve the product !

Quote: Originally posted by B(a)P  

When you do recrystallise, add less water than you know you need, take the mixture to around 100 C then slowly add water a little at a time while keeping the temp up until everything is dissolved (noting that you might have some crap in their that will never dissolve). If your solution is free of solids leave it to cool, once it is room temperature chill it down further for a few hours at least, then filter. If your solution has a little insoluble crap in the bottom decant into another beaker and do as above.

Textbook recrystallization :)
This is when everybody discovers the red / orange blob at the bottom of the beaker. Most will say filter the thing out but I agree with B(a)P. Decanting is just fine.
Usually a second recrystallization done in the same way will give you a product that is pure enough to be used as reagent.

Manyinterestests, after you filtered / decanted the solution of picric acid just let it cool slowly undisturbed. Dont walk around, dont breathe too hard around and wait until it has fully cooled down. Try this once before going to bed for example.
When left to grow undisturbed picric acid can be *really* amazing.
As you've noticed by now, the crystals will crumble when you filter them or when you move the beaker so you dont really have to worry about their aspect.
I think you've already notice this but the dry aspect of picric acid that has been recrystallized in different ways can vary wildly (your picture with the tupperware is a good example). The properties are exactly the same though.

For me, it was around that time that I stopped caring about the end result and started enjoying the journey much more.
The few seconds of exitement after a big bang are nothing compared to the road that leads to it.

Edit: now I've read the rest... Yes, omit step 6 !

[Edited on 15-12-2022 by Herr Haber]




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[*] posted on 15-12-2022 at 14:03


Yeah, I was making what should have been super obvious mistakes! Right now I ran into another complication... the weather outside (I do many of these on my balcony) is so cold that the large amount of water I am using for the picric acid recrystalization (and I will try to salvage what I can from all this) is so cold that the beaker doesn't boil, so I have to crank up the heat so much that maybe even the H2SO4 might be bumping slightly? Which I want to avoid...

The best time to make picric acid is the warm season!


Edit: Like I said, I am seriously contemplating just throwing out all the picric acid that I have... heck, even the one that I am recrystalizing now and just starting from scratch. The whole thing would have been a rather expensive way of gathering experience, but I think with the experience that I do have now it'll be much easier in the future... and much more pure.

The main thing is that I thought that the H2SO4 would be used up mostly in the reaction with the ASA. I was quite wrong in the assumption. Most of the sulfuric acid will remain I assume.

And all water will be added TO the beaker with the picric. No crashing. 3 times the volume if necessary. So 300ml of picric acid solution + 900ml of water? Or maybe a bit less. I need to know how much to make sure I get as much pure picric as possible.

Edit2: I think I'll keep the current batch, but I will need to see if I can make sure it isn't contaminated with the H2SO4. I won't get as much as I hoped, since I stopped boiling at 800ml (when ideally it should be around 600ml or so) and I transferred it while leaving the red blob and probably quite a bit of picric acid in my 2 liter. If it seems good and dries fast, then it should be OK, if not and it starts to degrade the paper, then I need to get rid of it.

I put the resulting stuff AND wrapped the beaker tightly in aluminum foil, in order to slow down the cool down and make some nicer looking crystals. Should I put it in the fridge once it gets to room temperature? I am thinking I don't want to contaminate the filtered yield with any bad picric.

I return to picric once the weather is not going to be as snowy as it is stated to be. I will process more ASA from my aspirin pills before I get to making any more picric acid. A few hundred grams of picric or bust! :D

[Edited on 15-12-2022 by ManyInterests]

[Edited on 15-12-2022 by ManyInterests]
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[*] posted on 15-12-2022 at 17:41


Quote: Originally posted by ManyInterests  

The best time to make picric acid is the warm season!


Urbanski tome 1 mentions that the French method he describes gives poor yields in Russia ;)

Quote: Originally posted by ManyInterests  

The main thing is that I thought that the H2SO4 would be used up mostly in the reaction with the ASA. I was quite wrong in the assumption. Most of the sulfuric acid will remain I assume.

It doesnt get used up at all: all the acid remains, it's just diluted as the HNO3 gets used up.
It's time to brush up on you maths skills. Sometimes you want the reaction to end at this or that concentration...


Quote: Originally posted by ManyInterests  

And all water will be added TO the beaker with the picric. No crashing. 3 times the volume if necessary. So 300ml of picric acid solution + 900ml of water? Or maybe a bit less. I need to know how much to make sure I get as much pure picric as possible.

That is still way too much water. Half or even less than half of your volume should be enough.
That will crash the PA out of the acid. Now you have to filter it but it's still saturated with H2SO4. A few rinses with small amounts of ice cold water will get rid of most of it. You can now recrystillize it.

Quote: Originally posted by ManyInterests  

Edit2: I think I'll keep the current batch, but I will need to see if I can make sure it isn't contaminated with the H2SO4.

If your product sticks together and remains moist after a proper drying then you know you still have H2SO4.

Quote: Originally posted by ManyInterests  

I put the resulting stuff AND wrapped the beaker tightly in aluminum foil, in order to slow down the cool down and make some nicer looking crystals. Should I put it in the fridge once it gets to room temperature?

You *can not move* your container while the crystals are growing if you want them to be big and look good. Any vibration will be *bad*.
The good thing is that if that happens you can just boil everything again as many times as needed.
Forget the Al foil, you want to see them grow :)





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[*] posted on 15-12-2022 at 18:44


Quote:
Urbanski tome 1 mentions that the French method he describes gives poor yields in Russia ;)


You know what I plan on doing? Right now I just want to get some of the stuff done, but when I do it I realize there is so much more happening than what any video could explain. Now that I have all four volumes, I will look through them and read them from time to time to try to fully understand the science behind all this, because it is a legitimately fascinating. So much to read, so little time. :)

But I do want to get a working system right before and then I'll research as to why it's a working system. I know it's putting the cart before the horse, but I've sunk so much time and resources into this that I want to get it done! :D Even if it takes another few weeks of work. Making picric acid is time consuming.

Quote:
It doesnt get used up at all: all the acid remains, it's just diluted as the HNO3 gets used up.
It's time to brush up on you maths skills. Sometimes you want the reaction to end at this or that concentration...



Quote:

That is still way too much water. Half or even less than half of your volume should be enough.
That will crash the PA out of the acid. Now you have to filter it but it's still saturated with H2SO4. A few rinses with small amounts of ice cold water will get rid of most of it. You can now recrystillize it.


OK, so no ice, just ice cold water and do it sparingly, so if I have 300ml worth of stuff, just around 200 or 250ml should suffice and then wash out the crystals when they're in the coffee filter with more ice cold water (to remove the sulfuric acid while keeping as much of the picric acid in the filter, maybe another 50ml or so (I use multiple filters, so 50ml per filter).

cool down the acid, add water, cooled down again, filter, wash.

Quote:
If your product sticks together and remains moist after a proper drying then you know you still have H2SO4.


Yes! That I have noticed Now I am aware of what is happening, I will account for it. Now I am far less interested in making picric as I am in understanding how to make it work properly and what is going on.

Quote:

You *can not move* your container while the crystals are growing if you want them to be big and look good. Any vibration will be *bad*.
The good thing is that if that happens you can just boil everything again as many times as needed.
Forget the Al foil, you want to see them grow :)


This is for all subsequent batches, right now I want as pure picric as I can get from the bungles I did. This one isn't super bungled so it should be OK. Wrapping it in aluminum did make for nicer looking crystals, but they crystalize REALLY fast I might add, but you probably knew that. :)
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[*] posted on 16-12-2022 at 07:48


What I find really great about Urbanski is the history / industry bits.
For a same compound he will describe how it was produced in several countries in WW1, will compare to WW2, why if relevant and so on.
You end up with several procedures and with a bit of thinking you will be able to design your own according to the reagents available. Sure, industrial production and laboratory scale production have nothing in common but it will help you understand what's going on nevertheless.
Picric acid is a fantastic example. You can start from phenol, ASA, Wintergreen oil... You can use a nitrate salt, WFNA, azeotropic HNO3 or even dilute acid etc...

What you coul do to crash your product is to add 20% of your volume (60ml for your 300ml example) of water and see what happens. Pour another 60ml if you dont get crystals after stirring but I dont think you'll need a third addition.
While they're in the first coffee filter (just use one, why more?) and damp with H2SO4 add very small portions of ice cold water to wash. Water will bind with the acid, have it as cold as possible so it doesnt dissolve your product.
Several small washes are better than one big.
This can be a pain in the ass if you dont have a vaccuum pump but can be done. Is this why you are using several filters, to avoid having to filter through a pig pile of PA ?

From there, if you recrystallize twice you will have very pure picric acid suitable for any of your needs. Tanning rabbit's foot for example... (yes, it was used for that too).

I'm pretty sure something if not most can be recovered from your bad batches through recrystallization. I'm starting to wonder if what we assumed was Al picrate forming wasnt just the small amount of H2SO4 reacting with the Al foil you used.
PA can form 6-8cm long needles overnight in summer. If you are going to play with a PA solution to grow crystals you can use an Erlenmeyer. Just heat, and let it cool again in different condtions. You lose more water with a beaker but you can always replace what boiled.




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[*] posted on 16-12-2022 at 17:59


That sounds good. I think my fourth batch will be OK. I left it in the fridge after leaving it out for 24 hours to cool. The crystals did form differently than normal due to retaining the heat!

I will also recrystalize the first two batches (I got 100 grams in total from them) I am OK with losing 10 or even 20 grams of picric in another recrystalization if it means I can get good, high quality picric acid.

The info you are giving me is very important. I will do it that way in the future. Let it cool fully outside the fridge, then put it in the fridge for a few hours... then add the water SLOWLY to see what happens.

I have one other question about water and recrystalization. Rosco's paper said to use around 2.75 liters for a starting batch of 100 grams of ASA. My largest container is a 2 liter beaker, so I cannot go that far. But can I use around 2 liters to recrystalize that much starting picric acid anyhow? Since I've been getting a lot of experience making picric acid, I can scale it up slightly to save time. It is a hectic, almost 24 hour process to go from initial synth to crashing it out to filtering, to recrystalization.


Edit: Yeah! My batch is fine. I should not have squeezed dry the coffee filter, since some fine crystals did seep through, I should have just let it dry in the funnel for a few hours before removing it.

But that's fine in the end of the day.

[Edited on 17-12-2022 by ManyInterests]
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[*] posted on 17-12-2022 at 06:54


Insulate the jars for first recrystalization, insulate them good, you want the slowest physically possible cools down.

Large well defined crystals make for much easier filtering and handling.

then once at room temp as gently as possible and still wrapped in insulation put them in the fridge.

It is all about patience!
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[*] posted on 17-12-2022 at 11:35


Quote: Originally posted by ManyInterests  

The info you are giving me is very important. I will do it that way in the future. Let it cool fully outside the fridge, then put it in the fridge for a few hours... then add the water SLOWLY to see what happens.


Add water add the end of nitration. No need to cool it down completely before that. Temperature will rise again when you add water so do it all at once. Besides, after the foaming your beaker's wall should be covered with crap that you can clean while adding that water.
Very important: Take all precautions when adding water to concentrated acid ! It's usually done the other way around for safety. I'm assuming azeotropic nitric acid is used. If a nitrate salt was used the leftover H2SO4 will also be more concentrated and maybe more prone to flash boil the water.

Quote: Originally posted by ManyInterests  

But can I use around 2 liters to recrystalize that much starting picric acid anyhow? Since I've been getting a lot of experience making picric acid, I can scale it up slightly to save time. It is a hectic, almost 24 hour process to go from initial synth to crashing it out to filtering, to recrystalization.

Well, 100 grams is quite a lot already. It's also bulky to filter so why bother scale it up ?

One solution (no pun intented but...) to your problem is to use a co-solvent.
Ethanol, methanol, isopropanol...
Dont expect miracles, look at the solubility curves to "guesstimate" what should be the exact % you have to use.
If you do that you will also get other crystal shapes that can be interesting.
(Just pleasing to the eyes mostly)

Another method would be to do this under pressure say in a *big* mason jar with rubber seal. If you use a solvent (other than water) use a water bath to heat everything. You cant go above 100celsius and if you put a spacer between your jar and whatever huge beaker or pot you have it should avoid stressing the glass or building too much pressure.
*Always* let it cool before opening the lid !
You dont wont a geiser of hot picric acid in alcohol in your face !




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[*] posted on 17-12-2022 at 15:06


Quote:


Add water add the end of nitration. No need to cool it down completely before that. Temperature will rise again when you add water so do it all at once. Besides, after the foaming your beaker's wall should be covered with crap that you can clean while adding that water.
Very important: Take all precautions when adding water to concentrated acid ! It's usually done the other way around for safety. I'm assuming azeotropic nitric acid is used. If a nitrate salt was used the leftover H2SO4 will also be more concentrated and maybe more prone to flash boil the water.


But I do need to wait a bit to let it cool down, and yes I do use a nitrate salt (sodium nitrate, but also potassium nitrate. My sodium nitrate supply is almost finished, so I will rely on my potassium nitrate for subsequent nitrations. I will need to purify more ASA for that, however, and I will be using 75 gram starting ASA and not 100. I realize it is too much. So I won't be trying that

I am extremely well aware of adding acid to water and not the other way around, that is why I am VERY careful when adding it. This is the only time I ever did that. The main danger isn't just the heating and flash boiling, it is also the NO2 gasses that it releases, which as you know, I hate to no end.

In fact, I will tell you in the next two weeks I will be ordering a gas mask with 3 different filter canisters in order to cover all my projects. Ammonia, acid vapors, and hydrocyanic acids. I will not go through any more unwanted inhalations.

I hope to continue doing these in the future, but for now I think I'll take a touch of a break,
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[*] posted on 18-12-2022 at 10:10


So on an unrelated note... despite my best efforts to keep picric acid stains off my floor (I covered as much of it as I could with aluminum foil I managed to get a lot of picric acid stains all over it. The worst one is a place that I thought wasn't going to get covered...

How that happened is the bad batch that was covered in picric acid infused sulfuric acid and the paper broke off and landed on my floor.

This is what happened. I know picric acid is a super powerful dye, but any way of getting it off? It's unsightly and I don't want to have to answer any questions to the landlord! :D

IMG_20221218_123251594_-_Copy.jpg - 1.9MB
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[*] posted on 18-12-2022 at 11:47


Yes, you definitely want it to cool down a bit at the end of nitration. I dont think anyone wants to add water to 120c spent acid ;)
Something cheap that will help your gas mask is... a fan to push out whatever you need out of a window.

I dont have any idea for your floor... I mostly had bad ideas to cover up these kind of stains as a kid. Woops, I bleached the floor ? Lets cover it up with copper sulphate !




The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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[*] posted on 19-12-2022 at 18:15


So in other news... I tried to extract more ASA from Bayer Aspirin pills (325mg) and the result are... questionable. In fact, I don't know what happened, but I don't want them.

thankfully I did find salicylic acid on amazon with very reasonable prices. I did some reading on urbanski and on powerlabs (an old article from 2000) on it, but I am not sure on the different proportions. Rosco says to use 1.8 grams of sodium nitrate per 1 gram of ASA, would a similar amount work? Or is a little more needed? I assume the same amount of sulfuric acid is also appropriate?

I am still trying to think of ways of removing those stains.
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[*] posted on 22-12-2022 at 19:42


OK so I decided to put my updated notes for the future as I will have to hold off on making picric acid for a few days (the weather is too bad) and that attempt will be the final using my old batch. It will be january before I restart everything as I will have my salicylic acid by then and more sodium nitrate made.

The yield I got from the 75 grams of ASA was only around 18 grams of picric. I know what you are thinking 'that's impossible!' and I would be inclined to agree, but I didn't want to take any risks with the contaminated dirty stuff I put in there during recrystalization. I still need to recrystalize the 104 grams I got from my first two batches to make sure THAT batch is 100% pure. I might lose a lot, but given that I plan on doing many more synths in January that is an acceptable loss.

So to recap the steps based on everything I've learned so far. (I know I might have written something similar above, but just to reiterate).

1: Do the sulfonation and nitration. This time it will be with salicylic acid and not ASA. Add a bit more nitrates just to be sure it is getting enough (2 grams sodium nitrate per gram of salicylic).
2: let the nitrated mix cool down to room temperature on its own
3: put in fridge until it is very cold
4: add a little bit of water, then cool down again, repeat the process, use around 50% of the volume of the nitration mixture in water.
5: Filter
6: wash the filtrate slightly with ice cold water
7: Dispose of the left over liquid (dilute and add sodium bicarbonate)
8: Recrystalize
9: After cooling, filter out the crystals, and continue to boil down the liquid for more crystals until nothing is left.

By the time everything is good again, I should have my gas mask and everything. The weather will be cold as all hell outside but that should aid in other nitrations like RDX and PETN where the cold is necessary, and recrystalizations can be done indoors.

Quote:
I dont have any idea for your floor... I mostly had bad ideas to cover up these kind of stains as a kid. Woops, I bleached the floor ? Lets cover it up with copper sulphate !


I am going to assume this is another joke. I won't be adding copper sulphate to the floor! :D

[Edited on 23-12-2022 by ManyInterests]
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[*] posted on 27-12-2022 at 09:22


Quote: Originally posted by ManyInterests  

Rosco says to use 1.8 grams of sodium nitrate per 1 gram of ASA, would a similar amount work? Or is a little more needed? I assume the same amount of sulfuric acid is also appropriate?



ASA is 180.15 g/mol but salicylic is 138.12 g/mol. The absolute bare minimum NaNO3 per gram of ASA is 1.4 g to render TNP. That's just a technical minimum, you would want to use excess beyond that. Rosco's recommendation is actually only a little over a third in excess, which is likely enough, but you can increase nitration speed by increasing nitrate proportion even beyond that. Anything below 1.4 g NaNO3 per gram of ASA will result in dinitro product. With salicylic acid, the minimum amount of NaNO3 is 1.78 g per gram of SA. So if you use 1.8 g as with ASA, you are no longer in much excess, it is technically enough but it is close, the bigger your batch and longer the nitration time eliminates contamination of undernitrated product but environmental factors/errors/spills could still give you some dinitro product, short time of nitration would be the biggest cause of dinitro. For salicylic acid, 2 g or 2.2 g sodium nitrate per gram of salicylic acid would be more optimal. That way you are in greater excess for eliminating dinitro contaminant. Dinitro product will result in a fairly lighter color but mostly the dinitro is less reflective than TNP. Dinitro is much more mat and not so sparkly.

H2SO4 is already in excess enough to have no difference between ASA and salicylic acid, the 4 ml / g of ASA seems it should transfer fine to salicylic medium. If the extra nitrate causes too thick mix, you can add H2SO4 to thin it.

[Edited on 27-12-2022 by Hey Buddy]
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[*] posted on 27-12-2022 at 18:21


OK that sounds good. I will put in 2.2 grams of nitrate just to be in excess and make sure everything is OK.

In the meantime I am having very serious problems with my aparatus. Especially heating control. The temperature on my mantle is seriously off. I need to use my 2nd thermometer to make sure it is OK.

I need to mention this. While I know picric acid is not chemically compatible with many metals... but I did see this that stainless steel (which is what my thermometers are made of) shouldn't be affected by picric acid and vice versa?

https://kelco.com.au/wp-content/uploads/2009/02/stainless-st...

The main issue I had in making the stuff is the fear I will form unstable picrate salts if it gets in contact with a bare steel thermometer, hence the time I took in getting everything to cover it.

Will I be doing anything dangerous if I take the temperature during nitration with a simple stainless steel thermometer or what? I need to know.

Edit: Does picric acid form picrate salts with metals when only dry or wet as well?

[Edited on 28-12-2022 by ManyInterests]
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[*] posted on 27-12-2022 at 19:18


Nitric acid mixed salt bath will erode stainless eventually. It does take a while, and it speeds up with neglect. Heat will wear SS faster, if it isn't cleaned right away it will eat away faster too. At some point it will erode under nitric conditions. I dont know what sort of contamination that would give to a picrate salt but it would have some trace contaminate at some point. Probably a chromium picrate salt would be sensitive, I'm not sure. Maybe you can find a better picric primary beyond DDNP by accidentally dissolving SS in the nitro bath. --Im joking.--I use only glass, ptfe and the occasional wood to touch my nitro baths.

edit: to be clear and helpful, I have done PETN nitrations with nitrate salt/H2SO4 on SS paddle mixer rods. They began noticeable corrosion after perhaps 3 nitrations or so, several hours each. I can still use them but I dont use them for corrosive applications any more only inert stuff

[Edited on 28-12-2022 by Hey Buddy]
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[*] posted on 27-12-2022 at 21:08


So I will have to work differently to make sure that I get everything working. Once I have my all picric acid done, I will install a new thermoprobe for my mantle (I have another one on the way, which should work well). This will take a while since due to me breaking my 2 liter beaker (it is cracked only slightly, but I will not use it since it might shatter), so I will need a replacement. In the meantime I will probably just do some basic reagent synth until I get my salicylic acid. (I am almost out of nitrate salts)

I made the final picric acid synth with my old ASA supply. This time I will do it right. I can't do a recrystalization, but I will NOT reuse the mother liquor. I am letting it cool down to room temperature before putting it in the fridge to let it cool down even more before putting in 50% of its volume in water before filtering. No crashing it in ice this time!

Edit: After leaving it to cool overnight (room temperature) it is actually not even a slush anymore. It is much harder. I don't think putting it in the fridge is necessary at this point. let's see what adding water to it (slowly of course) will do.

Edit2: Ok so I added 100ml of ice cold distilled water (in three separate additions). There was some heating and a faint smell of NO2, but no major flash boiling or danger. I am waiting for it to cool down again before I will add another 70ml or so of water and cool down in the fridge before filtering it out.

So far I am finding this method is vastly superior to the crashing method. Thank you Xeon and Herr Haber for that. Once I get my supply of salicyclic acid and new 2 liter beaker I will definitely use this method going forward.


Edit3: After adding all the water and cooling it down more in my fridge, I filtered out the crystals. the water that came out the other side was quite reddish. I used only a little more water as some of the stuff was stuck at the bottom of my beaker, and I did need two filters as they both got pretty clogged with the picric acid sludge. I tried to get as much liquid out as I could. The paper is not tearing up like it was when soaked with sulfuric acid, but I do believe there is still some acid left that should be taken care off in the recrystalization (I won't boil down ALL the liquid, just do a two step. First to purify and remove the dinitro and mononitros, then a 2nd time to squeeze more out but leave around 150ml to make sure all the sulfuric acid is gone.

Either way the yield I am getting here is FAR bigger than any previous synth. I am very proud of what is happening so far. And they are all nice and yellow. Now it's just letting them dry out naturally and seeing if the papers are too acid afterward. There is still probably quite a bit of sulfuric acid that needs removing, but they will be removed in the recrystalization I believe. If they don't dry on their own in a few days I know that there is a lot of acid left over. This means the next time I do this I will need to add in an additional 50ml of water or so.


[Edited on 28-12-2022 by ManyInterests]

[Edited on 28-12-2022 by ManyInterests]

[Edited on 28-12-2022 by ManyInterests]

[Edited on 28-12-2022 by ManyInterests]

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[*] posted on 30-12-2022 at 16:57


So after a couple of days of waiting, I realized that the sheets became SOAKED with residual acid. I am so glad I kept it under a vinyl dropsheet so I will not have to deal with any more stains on my floor (that big stain is probably not going away, but I will still try my best in the future to make it more unnoticeable).

I could have stood to wash my picric acid with a little more water. Not that much, maybe squirting like 60ml of ice cold water to force out more acid would have been preferable. I used very little water so I got a LOT of picric acid crystals. But there is still some undesirable acid in there, so I need to be very careful how I deal with it.

Next time I will add 200ml of ice cold water to start and won't be shy about washing it out with a little more to make sure everything is cleaned up. I want to start with as little acid as possible (if any) when doing the recrystalization step.



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[*] posted on 21-1-2023 at 02:46


Just giving this a bump. Since I've received my new 2 liter beaker I decided to return to this project. I took out the old 104 grams I made and I decided to do a full re-recrystalization of them in order to get some consistent crystalize sizes. I dissolved them in 2000ml of water and I boiled it down to 400ml and I am just letting it cool. there are next to no impurities that I see (the water is supposed to turn red when you heat it up, correct?) so I am just going to let it cool down on the mantle to see what lovely crystalize sizes I get. I also really hope that the heat didn't degrade any of the picric. I just want to make sure... when you boil something in a solvent (like water in this case) the whole thing doesn't go hotter than the solvent, am I right here? I feel like I should know this already.

For the latest synth I made. I noticed that the paper towels because fully saturated with acid. I mean FULLY. When I changed them, those paper towels became saturated as well, I changed them about three more times I believe and they much dryer. This is a long way to get rid of excess acid (and I am assuming most of the sludge is picric acid infused sulfuric acid) but it seems like it did get rid of most of the unwanted sulfuric. I will obviously need to be a touch more careful when recrystalizing this one and I will leave around 100ml of water from that to throw away and I am banking on that bit having the last of the excess sulfuric acid.


Edit: After boiling the water from 2000ml to 400 ml the crystals that were leftover took on a reddish color. I assume this was due to the heat. Is my picric decomposed or is it OK? It seems that the crystals were quite pure. Some may have melted down during the heating as my heating is wonky (it have been the boiling point of water but also the melting point of picric).

I am convinced now that this is as pure as they will ever get.

I took the remaining water (around 350ml) and I will evaporate it down until it is around 150ml or so, filter off whatever crystals I find, then discard the remaining liquid.

[Edited on 21-1-2023 by ManyInterests]

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[Edited on 21-1-2023 by ManyInterests]
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