Safety Services


Picric Acid

Picric acid is an organic compound. The name "picric" comes from the Greek word meaning bitter, reflecting its bitter taste.

Why this substance is hazardous

Picric acid (2,4,6-trinitrophenol) is explosive when allowed to dry out. The crystals that form are a Class 1 explosive and highly sensitive to shock, heat and friction.​
​If not stored in accordance with the reactive, compatibility tables, the resultant crystals may be picrate salts that have an even greater explosivity, e.g. lead, copper, zinc.​


Staining samples – reagent for Gram staining etc.​
Preparation of crystalline salts – useful for identification and characterization​

Recommended control measures​

This is a controlled substance (explosive) – see information on standards for all controlled substances.​

Use the more stable substances​
A 1% solution rather than wetted solid is a desensitize explosive and there are no requirements for a licence. However, it is still a controlled substance and UCL has to keep a record of how much it possess to enable the reporting of any unexpected or unexplained loss.​

Monitor the status of the solution​
Mark the bottle with the purchase and open on dates and store with at least 30% moisture. This requires regular checks (at least once a month). Record use and when water is added to maintain moisture levels. Check the cap and bottle for the formation of crystals which will be unstable picrate salts​

Contact competent person for waste ​
If there evidence that crystals could or are forming contact Estates – Hazardous Waste.​
No attempt must be made to open any container where there are signs of crystallisation, or where the picric acid has dried out, as detonation may result. Specialist explosives disposal service are required.​ Due to the resources needed to manage picric acid, do not keep with the intention of using it at an undetermined later date and dispose after the substance is 2 years old. ​  ​

Health surveillance ​


Chemical safety library

> Read more about control measures for chemicals in our chemical safety library 

Last updated: Thursday, June 24, 2021