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Picric acid: different instructions

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B(a)P - 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.

Herr Haber - 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.

B(a)P - 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.......

ManyInterests - 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]

B(a)P - 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.

ManyInterests - 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]

Herr Haber - 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]

ManyInterests - 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]

Herr Haber - 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 :)

ManyInterests - 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. :)

Herr Haber - 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.

ManyInterests - 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]

XeonTheMGPony - 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!

Herr Haber - 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 !

ManyInterests - 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,

ManyInterests - 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

Herr Haber - 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 !

ManyInterests - 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.

ManyInterests - 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]

Hey Buddy - 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]

ManyInterests - 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]

Hey Buddy - 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]

ManyInterests - 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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ManyInterests - 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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ManyInterests - 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]

B(a)P - 21-1-2023 at 13:19

Quote: Originally posted by ManyInterests  


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.



I would suggest discarding the whole 350 ml and everything it contains given the amount of acid you had. There will not be significant quantities of picric acid in it.

ManyInterests - 21-1-2023 at 15:10

Yep. There isn't. I evaporated it down to slightly under 200ml and it has been in the fridge for several hours and is near 0C. Nothing is coming out. I am going to dilute it, neutralize it with baking soda, then pour the whole thing down the drain.

I am quite proud of cleaning this up and getting consistent crystal shapes. I will be doing a recrystalization of the other batch I had lying around and slowly removing the sulfuric acid with lots of paper towel changes (so it is mostly acid free, but not quite. I will also need to recrystalize it to the 400ml level and then discard the rest, as THAT water is bound to have some H2SO4 left in it).

Then after that it'll be making picric acid using my potassium nitrate supply (since I am currently out of sodium nitrate and I am having some issues with synthesis) and using the salicylic acid that I bought off amazon instead of ASA (which I have no more of and I am not in the mood to through the expensive and laborious route of getting it from aspirin pills at this time).

I will be using 2.8 grams of potassium nitrate and 4ml of H2SO4 to 1 gram of salicylic acid. An excess for sure, but I want results. It wouldn't be the first time I made picric acid with potassium nitrate.

ManyInterests - 21-1-2023 at 22:27

OK so I recrystalized the final batch I did last December (before my 2 liter beaker broke) and I realized that sulfuric acid can be 'cleared' in a way with changing paper towels frequently. Granted that is a very slow and laborious way of doing things so I won't be repeating it. The paper was mostly clear once I dumped the picric acid into my new 2 liter beaker for recrystalization. It was made from 50 starting ASA, but I poured in 1800ml of water and boiled it down to around 475 or 500ml of water before decanting it. I saw the VERY red blob at the bottom that I was careful to leave behind.

I still see some redness in the picric. Is that a problem when I recrystalize or no? I'm legit curious here.

For the remaining liquid, since I am confident that there is going to be some H2SO4 still left in there, I will only boil down the recrystalization liquid slightly before seeing if there is any viable picric acid crystals I can save. Otherwise it will be discarded. The solution was still very hot when I took these photos so there is going to be a lot of coming out once it cools.

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ManyInterests - 13-2-2023 at 12:41

So I am back to making picric acid, this time my biggest synthesis. I originally just wanted to do 4 more 75 grams synthesis, but I decided it would be a waste of time and I could do 150 grams at a time.

I started using salcylic acid and I think it is MUCH better than ASA as I have done previously. I can't describe it, but it seemed to really work much better than ASA. More nitrates were needed, but that is not an issue I find.

So I had my gas mask on and maybe some of the fumes overwhelmed the filter and I ended up having some minor inhalation, but nowhere near as bad as the previous times. I fear that my filter is bust. I will be ordering a replacement in the future, but for now I will need to rely on it but also do what I did previously and maintain as much ventillation as possible, including doing as much of the nitration outside as possible as I did previously (NO2 inhalation was never an issue with my old system).

The main thing is that I learned really hard that the temperature MUST be kept up! While adding nitrates is an exothermic reaction. I noticed that it is not an exothermic reaction after 50% or so of the nitrate salts are added and the temperature will continue to drop. The result of this is that I had to put the beaker back on heating to get the temperature up to 95+C again. I also noticed that keeping the heating up does some good in keeping picric acid's well known foaming issue at bay. It does not eliminate it, but it does keep it more under control. I will need to do this for the future with my 2nd and final 150 gram synth as I nearly had a foam overflow. Reducing the amount of nitrate addition at a time will also do that. I do not like overflows!

I am committed on doing it a 2nd it even if the yield I seem to have here is very high. Like I was completely not expecting this kind of stuff. It must be salicylic acid since the nitrate salts I am using is from the previous batches. The sulfuric acid is obviously just the regular I've been using.

All in all I am VERY happy with all this. I will make another update next week after filtration and the 2nd batch is done. After that I will dry them and recrystalize them piecemeal since I cannot recrystalize this much picric acid at one time (my largest container is a 2 liter beaker. So 75 grams of picric is the most I can recrystalize at any one time).



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Herr Haber - 13-2-2023 at 13:40

Do it outside if possible.
NOx filters are not cheap, hard to find and dont last long. Prolong it's life by getting a more generic filter for your "every day use".

I remember you said you used one of Roscoe's synthesis. Apparently a short version (that works of course).
I think you would enjoy doing it in three steps "the slow way" at least once. That's just a personnal vibe I get from reading you. Plus, you'd be able to control foaming a lot more after that.

About adding nitrate and decomposition: of course you want to add a little at a time. Some of the NOx are unavoidable in this synthesis, but say you add too much nitrate in one go and you'll lose it as NOx too.
Nitric acid's boiling point is 83c, so if you're heating your nitration mixture at 95 some will get lost not matter what.

Good luck with recrystallization. I wouldnt want to be in your shoes, that's gonna be long ;)

ManyInterests - 13-2-2023 at 15:46

Quote: Originally posted by Herr Haber  
Do it outside if possible.
NOx filters are not cheap, hard to find and dont last long. Prolong it's life by getting a more generic filter for your "every day use".

I remember you said you used one of Roscoe's synthesis. Apparently a short version (that works of course).
I think you would enjoy doing it in three steps "the slow way" at least once. That's just a personnal vibe I get from reading you. Plus, you'd be able to control foaming a lot more after that.

About adding nitrate and decomposition: of course you want to add a little at a time. Some of the NOx are unavoidable in this synthesis, but say you add too much nitrate in one go and you'll lose it as NOx too.
Nitric acid's boiling point is 83c, so if you're heating your nitration mixture at 95 some will get lost not matter what.

Good luck with recrystallization. I wouldnt want to be in your shoes, that's gonna be long ;)


Yeah it is going to be long. I just started adding water to the whole thing. I calculated that there is around 1100ml in volume, so I will need 770ml of water to break everything up. It'll take a while to add everything since I need to do it piece meal and put it back in the fridge to cool down (I did see some warming after adding 100ml or so). I won't be having any of that flash boiling!

As for doing it outdoors. I want to and I will do it, but it is COLD. So I hope for a day that isn't too cold and I can do the entire thing out side. But I will also have to consider that I will need to heat it up. I am aware that heat degrades the nitrates, but one thing I am very much afraid of is that if I add the nitrates when they're cold, I will have a major runaway when I need to heat it up even a little. This actually happened to me once.

ManyInterests - 19-2-2023 at 16:09

So I did the final picric acid synth and after speaking with someone on a discord group with extensive experience in making picric acid and they told me to try something differently: instead of adding the nitrate salt while it is hot, I did it while it is cold, and this is the result. I haven't done the heating step yet, and I won't do it for another hour or so at least to make sure that nothing is going wrong. Albeit so far (around 30 minutes in) I see that it is going to be OK.

The NO2 was minimal compared to the last time, but it did happen. I was indoors the whole time and there is some NO2 scent in my apartment, but it is fading fast. I think it is going to be good.

I pray that no runaway will happen during heating. In order to prevent that, I must take absolutely sure that heating is done very, very, VERY gradually. No more than 10C increments at a time.


Edit: I saw a bit more foaming happening when I was waiting. I realize I need to give it many more hours to make sure all reactions that can happen have happened before heating. The last thing I want is a runaway with this much picric acid!
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[Edited on 20-2-2023 by ManyInterests]

Bert - 20-2-2023 at 13:13

Quote: Originally posted by ManyInterests  
So I did the final picric acid synth and after speaking with someone on a discord group with extensive experience in making picric acid and they told me to try something differently: instead of adding the nitrate salt while it is hot, I did it while it is cold, and this is the result. I haven't done the heating step yet, and I won't do it for another hour or so at least to make sure that nothing is going wrong. Albeit so far (around 30 minutes in) I see that it is going to be OK.

The NO2 was minimal compared to the last time, but it did happen. I was indoors the whole time and there is some NO2 scent in my apartment, but it is fading fast. I think it is going to be good.

I pray that no runaway will happen during heating. In order to prevent that, I must take absolutely sure that heating is done very, very, VERY gradually. No more than 10C increments at a time.


Edit: I saw a bit more foaming happening when I was waiting. I realize I need to give it many more hours to make sure all reactions that can happen have happened before heating. The last thing I want is a runaway with this much picric acid!


[Edited on 20-2-2023 by ManyInterests]


If you are doing this synthesis INDOORS without a hood/air handling, you are risking your health/life and possibly the health and lives of others.

Yes, you're likely to have issues as you heat the mixture. Foaming and/or a runaway are possible. But I'd worry more about your LUNGS.

Note on attached image that the sensory threshold may be as low as .1 ppm, but also note that in cases of slowly raised concentrations ABILITY TO SENSE LOWER BUT STILL DAMAGING LEVELS IS LOST. The max for a 4 hour exposure may be set at .5ppm, but you can't judge that by your sense of smell.

And it sounds EXACTLY like what you're probably going to be doing, trying to stretch this reaction out and run it without a proper hood and indoors.

Stop. Take it outside. Don't run such nitration reactions indoors unless you've got hood or other effective air handling equipment.

[Edited on 2-20-2023 by Bert]

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ManyInterests - 20-2-2023 at 20:10

I didn't have that many problems as you are describing, but I am really well aware of the dangers. I will never, EVER do another nitration indoors. No matter what. My gas mask stopped most of the gasses, but not all, which is why I didn't have much problems this time. But I am extremely well aware of the dangers. I have had NO2 inhalation issues and I REALLY FUCKING HATE IT!

I spoke with a doctor about it and they did advise more precautions.

I realize that I simply must take seasonal breaks if need be. Winter time is a problem in my area not just due to the cold but often times due to the snow (electronics and moisture don't mix well). I must accept that there is no shame in waiting a few months before doing something like this.

At any rate, my 2nd synth is fully complete, and the weather outside was well enough that I could do the heating step outside (and it was essential). I ran into difficulties with my thermometer which was often inaccurate, but I took great precautions to make sure that I was heating everything SLOWLY and in gradual steps to allow for any reaction to happen piecemeal and prevent a runaway.

When I heated it to 75C I decided to go all the way and when it reached 100C it did start to bubble with red NO2 gasses forming, but I did it outside and the wind was on my side so all dangerous gasses were blown away.

It has cooled down to near room temperature now and you can see it in the photo. I am not going to do any more picric acid synths for a very long time. I got too much already and nothing more to prove or explore with it.

I'll be fine, and I will be taking a break from most chemistry for a good long time to focus on other things.

For this and my previous synth, I will make sure everything is dried up before doing a recrystalization of everything and post my final results here when that happens.

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Herr Haber - 21-2-2023 at 03:54

A bit out of topic but anytime I used nitric acid and / or was exposed to NOx I could smell it almost everywhere for a few days.
Buses running on diesel smell specially strong.

ManyInterests - 21-2-2023 at 07:49

Quote: Originally posted by Herr Haber  
A bit out of topic but anytime I used nitric acid and / or was exposed to NOx I could smell it almost everywhere for a few days.
Buses running on diesel smell specially strong.


Yeah, I kept my windows open to ventilate and I remembered I could degassify by spraying bicarbonate solution. Which I did. my apartment is quite clear now. But like I said, while these two synths weren't as bad as the previous times, I need to make absolutely that I have no more inhalation going forward. I need to wait a while for the weather to get warmer before doing any more nitrations.

ManyInterests - 21-2-2023 at 20:39

OK so some final notes on this. While the final yield is obviously to be decided. I had to use a lot more water to crash out the picric acid because I could not break up the chunk that was at the absolute bottom. One thing I needed to keep in mind for the future (if I ever do this again!) is that I probably will need to add water to the acid BEFORE I put it in the fridge. Obviously the water must be ice cold and it must be added dropwise (for all practical purposes) as putting the picric in the fridge caused it to solidify both times. But in the first time I was able to breka up the chunks somewhat without excessive water. I was not able to do so in the second time in the end had to pour in boiling hot distilled water.

That's a note to self for the future.

ManyInterests - 24-2-2023 at 18:05

Wow. I dried out the batches separately. I am quite astounded. From my first 'hot' batch I measured out 315.60 grams from a starting 150 grams of salicylic acid, 600ml sulfuric acid (h2so4) and 270 grams of KNO3 (potassium nitrate).

my 2nd batch of similar reagents but double the distilled water (around 1300ml instead of 800ml water) is 242.52 grams. This means I ended up with a raw unrecrystalized total of 552.54 grams.

from 300 grams of salicylic acid this is a total of 1.8418 grams total. Even Rosco only made a total of 1.2g surplus, not 1.84. Then again, he started from acetylsalicylic acid, and not salicylic acid.

I am both proud and terrified of myself! Going to report the total weight after recrystalization.

[Edited on 25-2-2023 by ManyInterests]

ManyInterests - 26-2-2023 at 11:46

I got one question... I got a lot of left over liquid (which I will boil mostly down, but leave only a little left since I am confident that the remainder will have whatever is left of the sulfuric acid in it) but after boiling it down, and even when cooling down slowly, the picric has a reddish tint to it.

Is this a problem? did it degrade or something happen to it? I need to mention that in my previous synths using ASA There was a lot of blobs of impurities at the bottom, but in this circumstance, I find nothing. I believe this cold mean that I have some extremely pure picric acid right off the bat. But a recrystalization is always a good idea, if not to get some better crystal shapes.

But I am worried about the reddish tint to everything. Why does that happen? I know that when you dissolve picric acid in hot water the color of everything turns red, but is that an issue that I should be concerned about?

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B(a)P - 26-2-2023 at 14:45

Quote: Originally posted by ManyInterests  
I got one question... I got a lot of left over liquid (which I will boil mostly down, but leave only a little left since I am confident that the remainder will have whatever is left of the sulfuric acid in it) but after boiling it down, and even when cooling down slowly, the picric has a reddish tint to it.

Is this a problem? did it degrade or something happen to it? I need to mention that in my previous synths using ASA There was a lot of blobs of impurities at the bottom, but in this circumstance, I find nothing. I believe this cold mean that I have some extremely pure picric acid right off the bat. But a recrystalization is always a good idea, if not to get some better crystal shapes.

But I am worried about the reddish tint to everything. Why does that happen? I know that when you dissolve picric acid in hot water the color of everything turns red, but is that an issue that I should be concerned about?


I assume you are not trying for mass production here? The whole idea of taking the liquid off your crude crystals is to get rid of all of your impurities. Your liquid will contain all sorts of impurities and is best neutralised and discarded. If you chilled your initial reaction mix right down you are likely to be disposing of no more than several g of picric acid per litre. Best to focus on your crop of crude crystals and getting them purified. Trying to increase yield by extracting product from your waste solution is of no real value unless the desired product is high value or you are trying to optimise an industrial process. With energetics in particular obtaining a pure product is very important. You don't want to be introducing unknowns.

Edit - typo

[Edited on 26-2-2023 by B(a)P]

Herr Haber - 26-2-2023 at 18:02

It worries me that you synthesized such an amount. You dont need that much for proof of concept.
I agree with B(a)P, focus on purifying what you have. As for getting most out of the mother liquor, I'd say you reach a point quite fast where you have to invest a huge amount of time / energy for diminishing results. I'm not saying dont to it, it's educative and you can get interesting shapes from those crystals. But after doing it once and weighting the results you probably want to focus your efforts on your goal.

I reached this same conclusion with silver refining. I spend an awful amount of time to get all the silver out of solution. Litterally miligrams... And then when I spill the same amount on the table I just wipe it off with a sponge...

If you're worried about your PA still having some impurities just recrystallize it once more. Do the maths: how much PA you have, how much water you'll need, how much PA will be lost still dissolved in the water at room temperature ?
Not enough for you to care about it.
But man... I'd never want to recrystallize that much with just water. Is IPA / ethanol / methanol available for cheap where you are ? All would work as co-solvents. As for the ratios... well... eyeballing works as long as you've kept enough volume in your container to add more alcohol.
Hot filter, let cool to room temperature then filter out the PA. No need for a final wash. Drying should be faster than with plain water. I see in your picture that your PA is a bit damp. You can squeeze out water when picking it up with your disposable gloves. BE CAREFUL ! Dont break the filter ;)

Important note: if you use a co-solvent as I suggested PA form will be different than from water. IPA is cheap, some people dont recommend it because it makes platelets / scales that are "hard" to pour and to pack for maximum density.
Sieving through a fine plastic strainer will get you powder. Wear a mask while doing this or enjoy the bitterness of PA in your throat ;)

ManyInterests - 27-2-2023 at 20:03

Quote:
It worries me that you synthesized such an amount. You dont need that much for proof of concept.
I agree with B(a)P, focus on purifying what you have. As for getting most out of the mother liquor, I'd say you reach a point quite fast where you have to invest a huge amount of time / energy for diminishing results. I'm not saying dont to it, it's educative and you can get interesting shapes from those crystals. But after doing it once and weighting the results you probably want to focus your efforts on your goal.


I know how you feel. I had no idea I would end up with this much. My guess is that the Salicylic acid is so much better than the ASA that I used that I ended up with much, much more than I ever thought I would end up with. Most of the picric will end up in a bonfire when I am done with all this because I really don't need that much. I know it burns well but will not explode, which is important. Like I said, when I used ASA I didn't end up with this much surplus. I usually got roughly around what I put in, or even less (and that's only the crude yield. After recrytalization I ended up with far less as well). If I had known I would have gotten 1.84 grams per 1 gram of salicylic acid I would have done just one synth of 100 grams of salicylic as a 'final exam' and called it a day. I seriously underestimated what my final result would be, and it was likely due to the ASA I was using probably wasn't as pure as I thought it was. The salicylic acid I got? That stuff is as pure as it gets.

The mother liquor is gone. The stuff I will be boiling down is the liquid I used to recrystalize, but I will be leaving behind a few hundred ml to make sure that any left over H2SO4 is gone and ditto for any other impurities.

IPA and methanol are super cheap, and I have a good supply of 95% ethanol, too. For using water this stuff takes HOURS. I use 2100ml of boiling hot water (I preboil it before pouring it in the beaker) and then start the heating. Since it is already hot the heating won't be necessary. It takes around 4.5 or 5 hours to make it down to 700ml or so before I take it off the heat.

The picric is damp and I am willing to give it a squeeze. I learned that when filtering it I need to use 4 coffee filters on top of one another in order to make sure the filter is strong enough for a good squeeze with breaking. And I always use glove. I have lots and lots of disposable nitrile and vinyl gloves available. ditto for masks. I have lots of surgical masks to use in addition to my gas mask.

And I said it before and I will say it again. I am done making picric acid. I think after making all of this I have proved to myself that I can make it. I need to move onto something else! :D To be honest after this, most energetics making is starting to get repetitive and I might even retire from chemistry for a good long time. I still got other journeys to go on in energetics making, but those are for another time and another topic!

Edit: To a large extent seeing my yield made me think of the video from WessonSmith (the NHN guy who doesn't post here anymore) who has a video where he made what appeared to be dozens of grams (if not over 100) of NHN. That was... heart stopping!)

[Edited on 28-2-2023 by ManyInterests]

[Edited on 28-2-2023 by ManyInterests]

[Edited on 28-2-2023 by ManyInterests]

ManyInterests - 28-2-2023 at 22:11

Thanks Texium! I basically made this post a sticky!

That being said, I have recrystalized everything and I am very glad I did. While I tried to 'reclaim' more picric from the water I used to recrystalize it by boiling that stuff down... but I decided against it. I saw some shimmering in the water that, to me, was indicative of sulfuric acid that was still left over, and I decided that it was best to get rid of it. While I didn't squeeze out all the water from the recrystalized picric, the paper towels (of which I will need to replace frequently) should get rid of any remaining unwanted sulfuric acid. I neturalized everything with sodium bicarbonate (also got rid of the little bit of picric that remained) and poured it down the drain.

Also the redness appears to be gone. Maybe it was a temporary thing, but either way the color is more yellow now. I hope that now I have pure picric acid to turn into ammonium picrate. I really hope they are some good TNP this time.

[Edited on 1-3-2023 by ManyInterests]

ManyInterests - 13-6-2023 at 21:14

I am back at this because now I finally got around to making my own ammonia solution. After some mishaps (like creating a saturated solution and flooding my apartment with ammonia fumes!) I managed to make 1000ml of 24% ammonia solution. I feel very proud of my achievement. Next time I hope to hit the 28% concentration.

But that being said, when it comes to making ammonium picrate, as I have said previously, I know an excess of ammonia solution is needed. I have no problem dropping in a few hundred ml of this, but how much is exactly needed? like if I wanted to turn 100 grams of picric acid into ammonium picrate, would I need 150 grams of the ammonia? around 600ml of my supply?

ManyInterests - 17-6-2023 at 21:01

Since I cannot edit my last post I'll make a new one.

So I learned from Urbanski that there are two ways of making ammonium picrate. The first is with ammonia water (or as mentioned by XeonTheMGPony, bubbling ammonia gas directly into the solution), and taking a measure of the pH. Since picric acid is... well, an acid, once the acidity level starts to drop to a certain point, it should be all ammonium picrate at that point. It doesn't even need to be a very strong base, but around 9 or 10 is sufficient.

A second method and I learned this from Urbanski is... to use ammonium carbonate. I never thought of that, but if using sodium carbonate/bicarbonate will yield sodium picrate then... yes, it does stand to reason that neutralizing it with ammonium carbonate will yield ammonium picrate. Again, it is all about measuring the pH here.

I am thinking of getting some ammonium carbonate just to try that method out.

ManyInterests - 27-6-2023 at 21:03

OK, I used 77.5 grams of picric acid in around 1400ml of boiling hot distilled water. I started adding ammonium carbonate. I did not count how much carbonate I put in, but I stopped to take a pH reading and I was slightly over 9, but under 10. I didn't realize that the solution would still be fizzing even it reached alkaline levels.

I let it fully cool in the fridge after this and I filtered out the very nice golden yellow needle like crystals that are characteristic of yellow ammonium picrate. I still had 1200ml of liquid. I calculate based on the soubility of ammonium picrate that there should be around 8 grams of dunnite in the liquid. Right now I've evaporated the liquid at 90 Celsius until it is around 500ml. I think once it fully cools down, it should be around 400ml or so. I hope to salvage at least half those grams.

ManyInterests - 4-7-2023 at 14:07

OK the first attempt produced good quality ammonium picrate, but I should have dried to dry all the liquid to full dryness to pull out as many crystals as possible, as I only got around 41.5g of dunnite from the whole thing,

I did a 2nd attempt with another 77.5g (this time using the 'old' triple recrystalized picric acid that I had handy. I decided to do it with a 10% solution of ammonia instead of ammonium carbonate. I added 99ml of 10% solution, at first I put in only around 10 or 15ml, but I saw it immediately turning red, so I decided to jump dump the whole graduated cylinder all at once.

The pH was a good 9 right off the bat, and it was VERY red. Urbanski was right in that regard. Ammonia water is much more likely to make the red version of dunnite than yellow. It is a lesser quality, but just as powerful. I heard conflicting reports that the yellow is harder to set off, but others that say that the red is harder to set off. Either way I am gonna mix them together in the end of the day.

I will not air dry my picrate, I will dry it over a hot water bath, this is not only faster, but I also want to get as much yield as possible from this. I worked hard to get that picric acid and I don't want any of it going to waste! :D

Edit: It might not be the red version, I am seeing some yellow bits coming out of solution, but that could be yellow ammonium picrate and not picric acid. It could be picric, too, but I am not sure, the pH was quite strongly base.

Edit2: Nope, it isn't red ammonium picrate, it is the yellow version! Good! :D

[Edited on 4-7-2023 by ManyInterests]

[Edited on 4-7-2023 by ManyInterests]

[Edited on 4-7-2023 by ManyInterests]

IMG_20230704_192651538 - Copy.jpg - 1.9MB

axd1995 - 16-8-2023 at 18:56

I used 20ml of 92% sulfuric acid and 3.6g of salicylic acid. After heating, I added salicylic acid, but it couldn't completely dissolve. I raised the heating temperature and there was a strong phenol odor, but it still couldn't completely dissolve. Why?:(

B(a)P - 16-8-2023 at 19:23

Quote: Originally posted by axd1995  
I used 20ml of 92% sulfuric acid and 3.6g of salicylic acid. After heating, I added salicylic acid, but it couldn't completely dissolve. I raised the heating temperature and there was a strong phenol odor, but it still couldn't completely dissolve. Why?:(


How hot did you go? You need to get to 115 C to get it to fully sulfonated. It sounds like you have enough sulfuric acid, so my guess is you did not go hot enough.

DennyDevHE77 - 17-8-2023 at 00:55

Hello everyone, there is a recipe for the preparation of picric acid from sulphanilic acid without the use of concentrated sulphuric acid.

If anyone is not aware, I will give the methodology written out of the book "Laboratory preparation of explosives" by Solonin A.A..

"30g of sulfanilic acid is shaken with 250 cm³ of water and with 12g of sodium salt of nitrous acid. After careful stirring, carefully under strong cooling with ice water, about 100 cm³ of the cooled solution of 10 grams of sulphuric acid of specific gravity 1.84 g/cm³ in 100 cm³ of water is poured in.

After adding the sulphuric acid while cooling, the mixture is stirred from time to time for one or two hours, and left to stand for two hours at ordinary temperature. The obtained porous mass is filtered on a Buechner funnel, transferred into a beaker and then, with stirring and heating on a water bath poured 96g of nitric acid of specific gravity 1.38 g/cm³.

At the end of pouring nitric acid, heating is carried out until the end of gas emission and then left to stand for a day.

The released picric acid is filtered off on a Buechner funnel, washed with cold water."

There is a scheme of reactions (on the picture)

I was attracted to this method because sulfanilic acid costs about the same as phenol, and in general all substances are legal and easily available. Also, I'm currently experiencing some problems with concentrated sulfuric acid. But I still haven't found correct information on the yield. And also the exact temperatures are not specified, and I think there may be pitfalls here.

If someone has experience in synthesis of picric acid by this method, please share your experience, thanks in advance. Personally, in general, this method seems to me to work, but I do not expect large yields, as the molecule of sulfanilic acid is already heavy enough.

picric_acid_method.png - 14kB

[Edited on 17-8-2023 by DennyDevHE77]

ManyInterests - 7-9-2023 at 09:27

Quote: Originally posted by axd1995  
I used 20ml of 92% sulfuric acid and 3.6g of salicylic acid. After heating, I added salicylic acid, but it couldn't completely dissolve. I raised the heating temperature and there was a strong phenol odor, but it still couldn't completely dissolve. Why?:(


I would suggest using Rosco's picric acid method. The only thing is that you need more nitrate salt than for using ASA. But since you're using salicylic acid (which in my own opinion, is superior to ASA in every way, I think my picric acid was ultra pure even without a recrystalization when I made it with salicylic acid).

I would suggest using more sulfuric acid. I use 95+% sulfuric acid (I clean drain cleaner grade with H2O2 and then boil it for 95 minutes or so). Like 4ml for every gram of salicylic acid. this is a great excess, but I was able to fully dissolve all of my salicylic acid in H2SO4 before I even began the heating step, so I know it is an excess, but it will guarantee that you will be able to make it work.

Attachment: roscopicric.pdf (89kB)
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ManyInterests - 23-7-2024 at 01:27

I made a bit more picric acid, but one thing I did differently is that I used a lot more ice cold (near freezing) water to wash everything out. My losses weren't as bad as I thought they would be, but when I decided to a burn test, it was different.

How is picric acid supposed to burn? The last batch I did where I used burned like gunpowder in a puff, and it did that even after I recrystalized it (and I used more than needed water and didn't boil off a significant amount of the water when I suspected there was a lot of sulfuric acid in there) and after filtering it out (after cooling of course) it still burned really fast.

My current one takes a bit to melt, then it sizzles, and only towards the end it catches fire. with a lot of black smoke and a lot more flame than anticipated.

I am quite curious as to what is supposed to happen?

B(a)P - 23-7-2024 at 02:22

Quote: Originally posted by ManyInterests  
I made a bit more picric acid, but one thing I did differently is that I used a lot more ice cold (near freezing) water to wash everything out. My losses weren't as bad as I thought they would be, but when I decided to a burn test, it was different.

How is picric acid supposed to burn? The last batch I did where I used burned like gunpowder in a puff, and it did that even after I recrystalized it (and I used more than needed water and didn't boil off a significant amount of the water when I suspected there was a lot of sulfuric acid in there) and after filtering it out (after cooling of course) it still burned really fast.

My current one takes a bit to melt, then it sizzles, and only towards the end it catches fire. with a lot of black smoke and a lot more flame than anticipated.

I am quite curious as to what is supposed to happen?


Your second description is closer to how it should behave. First it melts, then burns with a sooty flame.

ManyInterests - 23-7-2024 at 05:58

Ok good. Seems like I am finally making fairly pure stuff. However I am a bit concerned about my old batch. While I did recrystallize that, it still did burn quite fiercely like gunpowder. I turned some of it into ammonium picrate to try to see if I can make a detonator strong enough to set it off (I used a 7mm Remington Magnum shell filled with 4 grams of melt-cast ETN and 0.4 grams of NHN/ETN mixed as primary). I tried one of those against a witness plate and it nearly obliterated the plate.

I am wondering why the other picric burned as it did, especially after recrystallization which should have removed all sulfuric acid residue.

I need to mention that the new batch used an excess of sodium nitrate. Around 2.5 grams of sodium nitrate per gram of salicylic acid instead of 2.1. Maybe the salicylic acid was fully nitrated in those batches? I am just speculating.
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