flinnsci.com SAFETY REFERENCE CHEMICAL DISPOSAL PROCEDURES
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FLINN METHOD
#10 Bases, Strong and Weak and Basic Anhydrides
Elementary neutralization of corrosive acid and base solutions is a generally
allowed disposal procedure. Two simple rules should be followed. First, the
neutralization process should be mild. Any strong acids or bases should first be
diluted to a concentration around 1 M or 10%. Second, the final product must be
near neutral (pH 5–9) before discharge to the drain. In this procedure, bases are
neutralized with dilute hydrochloric acid.
Examples
Ammonium hydroxide, sodium hydroxide
Materials Required
Hydrochloric acid, HCl, 3 M
Glass stirring rod
Ice/water slush (optional)
Large glass beaker
pH paper
Overview
Bases react with acids in aqueous solution to form a salt and water.
NaOH + HCl → NaCl + H2O
The neutral soluble salts formed are generally innocuous and can be rinsed down
the drain with water.
Procedure
1
Wear chemical splash goggles, chemical-resistant gloves and a lab coat or chemical
resistant apron. Use a fume hood if neutralizing ammonia solutions.
FLINN METHOD
#8 Azides and Azo- Compounds
Metal azides require licensed hazardous waste disposal as described in Flinn
Disposal Method #26c. Azides should NOT be drain-disposed. They react with
lead and copper in drain lines, solder joints and brass fittings to form unstable and
explosive products. Drain systems have been destroyed by such explosions. In
addition, azides are not biodegradable and will kill the necessary bacteria present
in the digestion system of wastewater treatment plants. Stocks of these materials
should be kept low. Sodium azide is a P-Listed acutely hazardous waste.
FLINN METHOD
#9 Carbon Disulfide
Carbon disulfide is a P-Listed acutely toxic hazardous waste (P022). Any discarded
commercial chemical product containing carbon disulfide as the sole active
ingredient will require licensed hazardous waste disposal. Proper management of
P-Listed wastes is extremely important because institutions that accumulate more
than 1 kg on site at anytime of acutely hazardous waste will be subject to the most
stringent requirements for listing, storing and reporting all their hazardous waste.
4
Rinse the neutral mixture down the drain with a 20-fold excess of water.
Flinn Method #6, continued
5
Filter or decant off the supernatant
liquid. Flush the liquid down the drain
with excess water.
6
Allow the solid to dry, place it in a plastic
container, and send it to a landfill.
2
Prepare a dilute solution of (1 M or
<10%) base by diluting a more concentrated
solution or dissolving the solid
into water. Considerable heat may be
generated when dissolving a solid
base. Use an ice/water slush if needed
to dissolve solid sodium or potassium
hydroxide. Ice/Water Slush
3
When solution is complete, slowly
add 3 M hydrochloric acid until the
mixture is neutralized. Check with pH
paper. More heat may be evolved in
the neutralization process. 3 M
HCl
pH Paper
Please… Read the Narratives
Important narratives precede these specific chemical disposal methods!
Please read each narrative carefully! Do not use these procedures if you are
not comfortable with the chemistry. Do not use these procedures without
first consulting with your local government reg ulatory officials. These
procedures may not be used in some jurisdictions. All procedures involve
some hazards and risks. Once again… read the narratives that precede
these specific chemical disposal methods.
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