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Subject: Re: pKa of Picric acid ?
From: (Arno Hahma) 
Date: Jun 27 1995
Newsgroups: sci.chem

In article <3sg5ic$>, Bill Nelson <billn@PEAK.ORG> wrote:

>: I'm sure you know this, but just in case: picric acid is explosive

>It is only very poorly explosive when dry, being less shock and impact
>sensitive than TNT.

Actually, picric acid is about twice as sensitive as TNT.  Its
sensitivity can be compared to that of hexogen. 

Still, picric acid is quite safe to handle if it is pure. The
laboratory containers are made of plastic or glass, so it is unlikely
the picric acid has been contaminated with metals.



Subject: Re: Help! Picric acid disposal
From: (Arno Hahma) 
Date: Jun 07 1995
Newsgroups: rec.pyrotechnics

>While on the subject of experts, just how many times have you disposed
>of old Picric?  

Many times. It's easy. Dry it, stick a blasting cap with a few cm of
fuse into it, light the fuse and throw. It makes a nice salute.  1/2 kg
cans are the best, you can throw them far enough to make them go off in
the air not having to use too short a fuse. Also, the shockwave from
that little is not overly strong but still makes a nice thump.

>Have you ever run into any which had formed crystals

Yup. Picric acid tends to be pretty crystalline stuff.

>(you know, the ones extremely susecptable to friction)?  Perhaps you
>were too busy avoiding the nasty fumes and got lucky.

Have _you_ ever even seen picric acid live?


From: (Gerald L. Hurst)
Newsgroups: alt.engr.explosives
Subject: Re: Picric acid safety
Date: 23 Jan 1996 19:16:46 GMT

In article <4e25r4$>, (bytestar) says:

>Isn't picric acid also known as Phenol?

Not until you nitrate it to make trinitrophenol. It IS known as
"carbolic acid," a venerable antiseptic found in many salves, etc.
It has the characteristic odor of medicated Vick's, somewhat like
that of the classic Listerine, which contains a structurally 
related compound.

Jerry (Ico)

From: (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: AP - sensitive or not
Message-ID: <>
Date: 9 Dec 91 22:17:56 GMT

Just to add about the sensitivity of picric acid itself.

T.Urbanski's "Chemistry and Technology of Explosives", vol. 1, p. 530
tells about accidents with it. In the USA a storage with 100 tons of
picric acid caught fire and the flame was 10 to 15 meters high. As
pieces of the ceiling structure fell on the burning mass, explosions
were heard, as large quantities of pressurized gas erupted. Still, the
whole mass did not detonate. Also, a very loud, characteristic,
whistling noise was heard.

That must have been a sight to see and particularly to hear: probably
the largest pyrotechnical whistle ever made ;-)!

Another example about picrates, a similar accident happened in England
1887.  Burning picric acid started flowing on the floor. As the
burning stream touched lithopone (red lead), it detonated. The molten
picric acid formed lead picrate, which immediately detonated and
ignited the picric acid.


From: (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: AP - sensitive or not
Message-ID: <>
Date: 10 Dec 91 08:54:03 GMT

>burning stream touched lithopone (red lead), it detonated. The molten
>picric acid formed lead picrate, which immediately detonated and
>ignited the picric acid.

One mistake... lithopone is not red lead, it is zinc sulphide, usually
mixed with barium sulphate. It is used as a white paint pigment.
Anyway, zinc and barium picrates are heat sensitive as well.

Sorry about the mistake.


From: (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: AP - sensitive or not
Message-ID: <>
Date: 9 Dec 91 11:13:23 GMT

In article <> (bill nelson) writes:

>>>>Ammonium picrate is shock sensitive and can explode.

>>>	Your right about ammonium picrate being shock sensitive, though.

>>Actually, ammonium picrate is NOT shock sensitive. It is remarkably

>> 'Ammonium picrate (explosive D) (AP) is at present used only where a
>>  high explosive is required that is particularly insensitive to shock.'

>On further research, my references are inconsistant.

>When the Picatinny Arsenal tested it, they came out with an impact
>height for a 2kg weight of 16-17 inches. TNT was 12-14" for the same

Ammonium picrate is less shock sensitive than TNT. In fact, it was
used before and during the WWII to fill armor piercing ammunition
because of its insensitivity to shock. The armor piercing here means
that the projectile first penetrates through the armor and then
explodes behind it. TNT was too shock sensitive for this purpose, so a
less sensitive and readily available (in that time) explosive was

The shock sensitivity is at least 20 joules (i.e. 1 meter height with
a 2 kg fallhammer), both T.Urbanski's "Chemistry and Technology of
Explosives" and R. Meyer's "Explosivstoffe" give the same value, at
least 20 joules. I have not measured the sensitivity myself, so I am
not able to give any more information.  The sensitivity of TNT is 12
joules, i.e. 60 cm with a 2 kg fallhammer, after BAM (Bundesanstalt
fuer Materialpruefung; at least one of 6 trials leads to an ignition).

Ammonium picrate is not used any more, since better explosives
are available. This is probably why data about it is scarce - no one is
interested in it any more.

>If we are to believe the PA, which I would, then the reputation for
>shock sensitivity may be due to the picrate getting moist while in
>contact with some metal.

Probably. Many premature detonations with artillery rounds have
occured because of this reason.

>Friction sensitivities were not listed for the other metals.
>(J.D.Hopper - using Picatinny Arsenal equipment)

T. Urbanski lists data for other metals also. All the values are much
less than that of ammonium picrate, usually in the order of 10..20 cm
for a 2 kg weight.

>According to Ellern (1968) the mixture of Potassium picrate and Potassium
>Nitrate (a whistling compound from Davis) is extremely shock and dangerous
>to handle.  The high sensitivity of most picrate mixtures was the reason
>for changing to KClO3 and Gallic acid mixtures.

The picrate whistle is indeed shock and friction sensitive. The gallic
acid formula is even more friction and shock sensitive. In case of a
detonation the picrate mass just detonates more violently causing more
damage. Also, the picrate mass is likely to detonate without warning,
whereas the gallic acid is likely to warn by crackling first. This is
not a rule, however.

>>worth losing ones eyesight or life. But I also believe that compromising
>>the truth is ALWAYS compromising the safety, too.

>I agree. As you can see, the researchers don't agree too closely. Part of

So do I. The researchers often do not give the safety measures, since
that would just "waste" space. They usually assume the reader knows he
is reading a potentially dangerous information and uses it
accordingly. This is why the books don't list the dangers too well.

>using it. I personally would not pound any picrate into the whistle tube.
>I would press it firmly - that should be all that is necessary.

That would also yield a better whistle than ramming it.



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