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topic 0724

Picric Acid Replacements


We use minor amounts of Picric Acid (Trinitrophenol) as an etchant prior to non-destructive testing. We are looking for a replacement for this. I am aware that Hydrochloric (Muriatic) Acid is used as an etchant on concrete. Any experience with Hydrochloric Acid in NDT work? or any other possible replacement for Picric Acid, regardless of use?

Any help would be appreciated.

Thank you,

Tim Dunn
- Portsmouth Naval Shipyard, Portsmouth, New Hampshire


The best list of micro and macro etchants that I have personally seen is from LECO in St Joseph Mi. It is in their metallographic preparation manual. They obviously sell metallographic equipment and supplies. An alternative is the metallographic book, one of a set, by ASM. "Principles of Metallographic Laboratory Practice" [link is to product info at Amazon], third edition or later, McGraw Hill is another source (this is an extremely old book)

I hope you are aware that dry or very nearly dry picric acid is an explosive, War I and II vintage.

James Watts
- Navarre, Florida


Dear Mr.James Watts,

I'm a student at Rajabhat Institute Petchburi Wittayalongkorn in Thailand.I want data about picric acid and I hope you help me. If you help me please send your data.

Thank you very much

somjai jetja - rajabhat institute
petchburi, wittayalongkorn, Thailand


I want to know what picric acid is used for in a Lab setting especially in a hospital and what substitutes I can consider replacing it with. How much should it cost to dispose of 20 grams? How explosive is 20 grams that are dry?

Thanks for any help you can give me.

Angie Jones, Safety Officer
- Mission St. Joseph's Hospital - Asheville, North Carolina


Any size bottle of unregulated picric acid (One that nobody will own up to and say they use it on a regular basis) is enough to trigger a cleanup crew to come and get it.

It should take 4-8 hours of special lab pack personnel and evacuation of the room prior to moving into the area. After it is gone, and nobody owned up to owning it, just make it a capital offense to purchase, possess, or store. Then you will find out if anyone needs it. Random inventories of the chemical shelves by the safety department is a good idea.

tom pullizzi monitor
Tom Pullizzi
Falls Township,


In Florida we have a hazardous waste exchange service where anybody can list material that they want to get rid of. I sort of doubt that very many people would be looking for Picric acid, but you never can tell.

A small lab-pack will probably run you about $300 to get rid of.

Picric acid is very docile when damp or slightly wet. Carefully remove the cover and spritz it with a squirt bottle. Mix with a glass rod, slowly, and add more water as necessary to get all of it damp. It has an excellent storage shelf life in this form and is nonexplosive.

James Watts
- Navarre, Florida


Picric acid in crystal form is a shock sensitive explosive. If there is any doubt that crystals may have formed on the threads between the container and cap, DO NOT attempt to unscrew it. This is particularly true if no one claims the container, knows how old it is, or when it was last used. Also, if the container has a metal lid, metal picrates may have formed on the lid or threads. Metal picrates are also explosive.

Do a google search on picric acid and you will find documents indicating that picric acid is a Class A explosive (OSHA) and that simply turning the lid on an old container may initiate an explosion. Call your Haz-Mat team in if you have any doubts. It's better safe than maimed or dead.

Len Voo
Regulatory Agency - New York, New York

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