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ManyInterests
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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
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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?
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B(a)P
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| 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.
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ManyInterests
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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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ManyInterests
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| Quote: | | 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. |
OK, so one thing that got me thinking. I asked an AI about using that kind of excess nitrate after I noticed one thing: the color of the picric acid
was more reddish than yellow after using an excess of nitrate, even if everything else is done. Also when using potassium nitrate it does burn with a
lot of crackling instead of melting and burning with a sooty burn.
The AI told me that an excess of nitrates could actually interfere with the purity of the picric acid. This made me think that in the future when
making picric acid using a nitrate salt, one should not added an excess. Towards the end, when adding more nitrate than necessary, it just goes to
making NO2 apparently instead of more foaming and CO2 as what happens.
Also one thing I need to mention is that I also heated the picric more than 120C, I went to 124C in order to go slightly above the melting point of
Picric acid. But the AI also said that going above can cause decomposition of the picric acid. I did go as high as 126C, but not for long. There was a
time when I had it go to 130C, but it was due to the excess of nitrate that caused another reaction, meaning if that is done, you'll need to heat it
to close to 120, but then let it cool before heating back it to ride out whatever secondary reactions before the final heating and cooling step.
Either way, recrystalization is critical for purity. Multi-Solvent, according to the powerlabs article on picric acid. 1:2 of ethanol and water. I
will recrystalize some of the old batches I have just to see what happens. I had them lying around for a while (safely stored, don't worry) and I just
wanna do one more experiment before neutralizing them and getting rid of them.
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