Sciencemadness Discussion Board

Picric Acid And Styphnic acid Problems

The_Davster - 2-10-2004 at 21:01

Recently I ran out of the picric acid that I had prepared around 6 months ago. So, of course I had to prepare more. My procedure was as follows(based a bit on the powerlabs synthesis);
1. 10g ASA was disolved in 20mL 98% ACS sulfuric acid and was heated at 100C for 1h by means of a water bath.
2. The resulting product was cooled, along with 30mL 70%ACS nitric acid in the deepfreeze
3. When their temperatures had dropped below zero the nitric acid was added very slowly(drop-by-drop) keeping the NO2 evolution to a minimum while in a water bath
4. The flask was removed from the waterbath and allowed to sit for a week with occasional swirling
5. It was then dumped into 120mL of ice water
This is where things started to go weird, I recieved no precipitate, and the solution was almost black. I managed to get a precipitate once I dumped this into 500mL of ice water but even then the precipitate was black/brown. I filtered this and attempted to recrystalize from water. However even when cooling to solidification after filtering the hot liquid during recrystallization I obtained no precipitate, but now the liquid was slightly redder. I am currently evaporating some of this liquid.

Problem number 2
I tried the powerlabs styphnic acid synthesis. I followed the procedure exactly only half the scale
Yet again my problem occured upon attempting to precipitate. I recieved no yellow precipitate, only, yet again, a black solution which upon cooling in the freezer still has precipitated nothing:mad:

Edit: Forgot to mention but when a bit of either the picric or styphnic acid solutions are added to water the solution still turns the expected yellow and both also stain yellow. So there is the acid in there.

[Edited on 3-10-2004 by rogue chemist]

JohnWW - 2-10-2004 at 22:20

What did you blow up with the picric acid you made 6 months ago?
BTW It, styphic acid, and some other aromatic nitro-compounds, are also used as yellow dyes, as well as explosives.

John W.

Mephisto - 2-10-2004 at 23:25

The nitrating acid often destroys the desired product by reacting further with it after a too long time. Thats the reason, why nitrated products had to be washed thoroughly to remove all traces of the nitrating acid. So, stirrung the mixture one week isn't advisible.

Did you let the styphnic acid mixture also stay for a week?

The_Davster - 3-10-2004 at 08:41

JohnWW, I was not using the picric acid as an explosive by itself, I was experimenting with a few picrates after having the vial of picric acid sitting on a shelf unused for months. The last .1g of my picric acid was used to make hexamine dipicrate.

Mephisto; The styphnic acid, after adding the nitric acid to the sulphonated resorcinol was left outsidde for around 20 min with occasional stirring. When I came back outside to stirr once the reaction mix had frothed up with an orange foam on top and a black liquid on the bottom. This is when I brought it back inside. Surprisingly I was unable to smell any NO2 during the entire styphnic acid procedure.

[Edited on 3-10-2004 by rogue chemist]

Styphnic acid

Mephisto - 3-10-2004 at 09:36

I don't know what could be the failure in your styphnic acid synthesis. Maybe too high temperatures and thermal decomposition, in this case (black reaction-mixture...). The orange gases were certainly NOx. Please post more details, and I'm sure, someone will find the bug.

It was only two years ago, when I also tried out this method. Fortunately I found the pictures, which I've taken, on my HDD.

The sulphonated resorcinol (lilac color) with some droops of nitric acid.

More nitric acid and NOx.

Here you can see, that the mixture shouldn't be black.

Precipitation in water.

The_Davster - 3-10-2004 at 09:55

Mephisto there was an orange foam after addition of all the nitric, not orange gasses. Even when the foam was broken up I was unable to detect any smell of NO2. Where as with the picric acid after slowly adding the nitric acid it continued creating NO2 for a week, which is why I let the picric reaction mix sit for a week, I assumed the reaction was not finished.
My nitric acid has turned very slightly yellow but the yellow color is inly visible when it is in the bottle. The nitric appears clear while in a graduated cylinder.


Mephisto - 3-10-2004 at 12:09

The mixture didn't evolves NO2-fumes even when heated on the heat source?

Your nitric acid was ~68% and you did your synthesis mostly like the 'powerlabs'-procedure, right? (The slightly yellow color of your nitric acid isn't a problem.)

The_Davster - 3-10-2004 at 12:18

Nope, no fumes at all during the entire final heating for 1.5h, I was able to do this inside without any means to get rid of any NO2 fumes.

And, yes the powerlabs procedure almost to the letter only 1/2 the scale. He is unclear whether to add the nitric all at once or slowly.

Mephisto - 4-10-2004 at 01:11

The nitric acid had to be added in such a rate to avoid a higher temperature of the mixture than 30 °C.

*[According to US patent 2246963 (large scale process)]