number of relatively common chemicals and reagents can become
explosive when stored improperly for excessive periods of time.
The following policy provides a list of the most common
potentially reactive/explosive hazardous chemicals and provides
information on how to prevent explosive hazards.
1. Peroxide Forming Chemicals
A variety of chemicals can form highly explosive
peroxide compounds as impurities when exposed to air over a period of
time. This problem is most common in ethers, but also occurs in a
variety of other organic compounds as well as in some alkali metals and
amides. As a result, great care must be taken to prevent the formation
of peroxides in these chemicals.
Preventing the formation of
peroxides is dependent on careful inventory control of peroxide forming
chemicals. Most peroxide forming chemicals are sold commercially with
inhibitors to prevent the formation of the peroxides. These are
effective until the container is first opened. After a container is
opened, the chemical comes in contact with air and may begin to form
peroxides. Therefore, there are two steps to prevent the hazards of
The first step in preventing the formation
of peroxides is to date all containers of peroxide forming chemicals
with the date the container was first opened.
The second step is
to dispose of the peroxide forming chemicals within six months of the
date the container was first opened. Manufacturers often state warnings
on their peroxide forming chemicals. In this case, the chemicals should
be dated and disposed of in accordance with manufacturers
recommendations if more restrictive that the six month disposal limit
set by EHS.
The following list is composed of potentially
reactive/explosive peroxide forming wastes:
Allyl ethyl ether
Allyl phenyl ether
Diethylene glycol diethyl ether
Dimethyl isopropyl ether
Ethyl Methyl ether
Ethylene Glycol Dimethyl Ether
Ethylene Glycol Ethers
Methyl isobutyl ketone
Organic ethers >1 year old
2. Picric Acid and other Polynitroaromatic Compounds
Picric Acid is commonly used in labs and is relatively safe in the form
which it is sold. It is ordinarily sold with 10% water added for
stabilization. However, picric acid can become explosive when it is
allowed to dry out or when it forms certain metal salts. The following
steps should be taken to safely store picric acid:
STEP 1: Never
allow picric acid to be stored in containers with metal caps or come in
contact with any metal.
STEP 2: Check Picric Acid frequently to ensure it remains damp. Add
water if needed.
STEP 3: Never attempt to open a bottle of old or
very dry picric acid. Contact EHS if this occurs.
Contact EHS for handling and storage information if other
polynitroaromatic compounds are used in your laboratory.
3. Tollen's Reagent
Tollen's Reagent (ammoniacal silver nitrate) can form highly explosive
silver fulminate over time after it has been used. To avoid this
problem, add dilute nitric acid to Tollen's Reagent immediately after
use and contact EHS for disposal.
4. Sodium Azide
Sodium Azide may form highly explosive heavy metal
azides if contaminated or used improperly. Disposal of sodium azide
solutions to the sanitary sewer may cause the formation of lead or
copper azide in the plumbing which could potentially cause a serious
explosion. Sodium Azide should never be heated rapidly or stored in
containers with metal components.
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