Materials Science & Engineering Safety Policy
For Handling and Storing Picric Acid
This document is intended as a reference for the department of Materials Science and
Engineering personal working with Picric Acid.
Picric Acid when dry and crystals formed are extremely dangerous; if there is a sudden
impact or pressure is applied the picric crystal could explode. For this reason the contents of the
bottle should always have a layer of distilled water on the surface; also the threads should never
have crystals on it! The bottle should have a minimal of 30% water in the bottle at all times.
Picric acid is toxic by all routes of entry (i.e., inhalation, ingestion, dermal), it’s also a
skin irritant and allergen and will produce toxic products on decomposition. After each use the
threads should be wiped with a wet cloth and the lid be rinsed with distilled water to ensure that
any picric acid is removed, and the cloth should be washed thoroughly to ensure that no crystals
form on it, and dispose this cloth into the Waste Disposal Bottle. YOU MUST HAVE READ
AND UNDERSTOOD THE MSDS BEFORE USING PICRIC ACID.
Incompatible Chemicals:
Picric acid is incompatible with strong oxidizing agents, bases, most common metals,
ammonia, most heavy metals salts (Nickel, Lead, Mercury, Copper, and Zinc), and strong
reducing agents; and is extremely susceptible to the formation of picrate salts when in contact
with the aforementioned. Many of these salts are even more reactive and shock sensitive than
the acid itself. Picrate salts are formed by the reaction of picric acid with any of the following:
metals, metal salts, bases, ammonia and concrete. Particular attention must be paid in order to
prevent the formation of picrate salts during normal use of picric acid.
Storing of Picric Acid:
The picric acid is stored in the flammable storage unit in room JHE 240, separated from
other reactive chemicals and contained in a secondary container. When using picric acid you
MUST inform a MSE technical staff person and prove that you know the dangers of this
substance and you have read and understood the MSDS. Weigh out the picric acid in a fume
hood. Users CANNOT access the bulk picric acid after work hours (if you need to make an
etchant do it before 4:30 Monday to Friday). Any etchants made of picric acid cannot be stored
for more than 4 hours. Each month the bottle must be inspected and a sign out sheet checked to
notify users that the bottle is safe to use.
Old Containers of Picric Acid:
Potentially old picric acid is an item of special concern and garners considerable attention.
If old or previously unaccounted for bottles of picric acid are discovered, the following steps
should be taken.
· Most importantly DO NOT TOUCH THE CONTAINER! Depending on how long the bottle
has been left and the state of the product inside, even a minor disturbance could be dangerous.
Crystals may have formed between the lid and the container. Any attempt to open the container
could result in an explosion large enough to do serious damage to personnel and equipment.
· Visually inspect the container for product identification and check for an expiration date. If the
product is relatively new, there may not be a problem. Nevertheless, treat the situation carefully.
· Inspect the contents of the bottle to determine water content and check for signs of
crystallization inside the bottle and around the lid. If there is no evidence of crystal formation
and the water content is fairly high, there is probably little cause for concern. If there is even the
slightest indication of crystallization or low levels of water in the bottle, the situation is more
serious. Contact MSE Staff immediately for guidance!
Immediately secure the area and restrict access. A measure of security can be obtained by lightly
misting any attainable crystals (such as those that may have formed on the outside of the bottle)
with large quantities of water. A water spray bottle is ideal for this purpose.
· Dry picric acid or picrate salts should not be touched or moved under any circumstances. This
is a serious potential hazard.
Etchants:
When working with picric acid etchants, the etchants shouldn’t be stored for more than 4
hours; but if you need to store the etchant it MUST be stored in a polypropylene bottle and
labeled. Ensure that there are NO crystals on the thread of the bottle and no crystals on the wall.
Once etching is complete the area must be completely de-contaminated; any glassware must be
washed thoroughly and any remaining etchant MUST be either disposed of in the Acid Waste
container or properly stored in an appropriate container. The container which was used for
mixing etchant must be cleaned and ensure that the threads on the bottle are clean from any
picric acid.
Dangers of Picric Acid:
1. When weighing out picric acid you MUST use a wooden spatula or plastic spoon!
Concentrated picric acid will react violently with metal.
2. Any dry crystals are extremely dangerous, if there are crystals either in the bottle or
on the thread of the bottle immediately get a MSE staff!
3. Never use a metal container to measure out picric acid; ALWAYS use a
polypropylene bottle and make sure that container is properly labeled.
If anyone is found not following the safe practices of working with Picric Acid or any other
harmful chemicals they will be banned from using the Laboratory!
Questionnaire:
1. Name two things which are incompatible with picric acid.
2. How do you extract the picric acid from the bulk bottle?
3. When finished extracting picric acid from the bottle what three things must be done
before placing the picric acid bottle back into storage?