University Safety and Assurances

Picric Acid Safety

 

General Information

Picric Acid

Picric Acid is distributed by the manufacturers wet with greater than 10% water. It is a tri-nitro compound that is normally classified as a flammable solid. As the water evaporates over time, the substance becomes dry picric acid crystals. Dry picric acid is highly explosive especially when it is combined with metals such as copper, lead, zinc and iron. It will also react with alkaline materials including plaster and concrete to form explosive materials. This material is shock sensitive and corrosive to metal containers.

Picric Acid is often found in science laboratories and chemical storage rooms and is used for staining of cells during biology experiments.

Identifying Problem Containers

The normal appearance of solid picric acid is a fine, moist yellow powder, with the consistency of a clumpy paste, which tends to adhere to the sides of the bottle. Picric acid makes a clear yellow solution, sometimes with undissolved solid powder in the bottom. Whether a solid or in solution, there should be no crystals.

Caution! If there are signs of crystalline material in the bottle neck, threads, or around the cap; or if the product inside appears powdery and to have dried out completely, do not move or handle the container and contact University Safety and Assurances staff for assistance.

Inventory Management

Purchase picric acid in quantities of no more than 100 grams to increase the likelihood that it will be used up before it becomes a problem. Store picric acid at a controlled temperature in a visible location within a flammables storage cabinet.

When receiving fresh product from the distributor review the MSDS for a material description and manufacturer's handling recommendations. Visually inspect the container. Do not open or use the product if it has exceeded its manufacturer's expiration date or does not appear normal.

Do not break the seal on the container until the product is needed. Label it with the date it is first opened. Add additional deionized water to solid picric acid as soon as it is first opened. If it does not interfere with its intended use, add enough water to immerse the product.

Use

Visually inspect the container for problems prior to each use and on a periodic basis (not less than every semester). After each use, take care to wipe down the bottleneck, cap and threads with a wet cloth before resealing. Thoroughly clean and rinse any secondary containers used immediately following the procedure. Add distilled water as needed to maintain its wet condition.

Maintain a log of the product's use and any water additions. This record will aid the Environmental Affairs staff in determining how to best handle the product for disposal.

Picric acid reacts with many metals to form highly unstable and shock sensitive metal picrates. Do not allow picric acid to contact metal that is readily oxidized. Do not transfer it to a container with a metal cap, or use a metal spatula to dispense it. It also reacts with calcium from cement floors to form shock-sensitive calcium picrate.

Read the Material Safety Data Sheet (MSDS) for the product or reagent that contains picric acid. Be sure it is the MSDS for the specific formula you are using. Call the supplier for additional information if necessary.

If a container of Picric Acid of unknown vintage is found, DO NOT attempt to open the container. Treat ALL containers of Picric Acid as if the acid has dried. The container could explode from friction on the crystals between the grooves of the cap and the threads.

If anyone has Picric Acid stored in their labs, please consider getting rid of it. You can request a pickup by completing the on-line E-Request for Chemical Waste Pickup or by calling x2883 or x4999. If you haven't used the Picrid Acid recently, please do not move it or disturb the cap in any way. Picric Acid is now sold in a 1% solution in water, which is much safer, but you still have to watch out for crystals forming under the cap. When Picric Acid is purchased, put the date received on the bottle. Dispose of any Picric Acid over 1-year old.

For further information contact your professor, supervisor, principal investigator or the Environmental Affairs Program staff located in Lapham Hall, Room 248 (x4999 or x2883).