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Flinn Method #23, continued
SAFETY REFERENCE CHEMICAL DISPOSAL PROCEDURES
4 Procedure
Allow the solution to sit overnight in the fume hood. Flush the entire solution down
the drain with a 20-fold excess of water.
Note: This procedure is not intended for use with hydrogen sulfide gas. Gas
cylinders must be used completely, vented into a ferric chloride solution through a
trap, in an operating fume hood, if needed (due to a leaking valve, for example) and
then disposed of in the trash. Small lecture bottles cannot be reused.
1
Perform this procedure in a fume hood. Wear chemical splash goggles, chemicalresistant
gloves and a lab coat or chemical-resistant apron.
4
Adjust the pH of the mixture to 5–9, if needed, and rinse the solution down the drain
with an excess of water.
FLINN METHOD
#24b Acids, Inorganic
Neutralization of acid and base solutions (corrosive wastes) is a generally allowed
disposal procedure and should present minimal problems. Two simple rules should
be followed. First, the process should be mild. Any strong acids or bases should first
be diluted to a concentration around 1 M or 10%. Remember, always add acid to
water. Second, the final product must be near neutral (pH 5–9) before discharge to
the drain. In this procedure, acids are neutralized with sodium carbonate.
Examples
Hydrochloric acid, sulfuric acid, nitric acid
Materials Required
Sodium carbonate solution, Na2CO3, 1 M
Glass stirring rod
Large borosilicate glass beaker less than 1⁄2 full of water
pH paper
Overview
This procedure is a standard neutralization of an acid with a carbonate.
Neutralization may be highly exothermic. Immerse the reaction vessel in an ice
bath to control the temperature, if needed.
2H3PO4 + 3Na2CO3 → 3CO2 + 2Na3PO4 + 3H2O
FLINN METHOD
#24a Acids, Organic
Organic carboxylic acids can be disposed of by neutralization, solid waste disposal
or incineration. Water-soluble organic acids are best disposed of by neutralization
with a base to form water soluble sodium salts. Solid, long chain carboxylic acids
(e.g., lauric, decanoic) and their salts are insoluble in water, but small quantities
pose little risk to the environment. These can be disposed of using Flinn Disposal
Method #26a. All other organic acids are best disposed of using a licensed
hazardous waste disposal company. Note that all liquids having a pH ≤2 are
classified as corrosive wastes and must be neutralized prior to drain disposal.
Use Neutralization Method for These Acids
Acetic acid
Aceto-orcein solution
Barfoed’s reagent (Copper carbonate may be formed. Filter and landfill.)
Formic acid
Fumaric acid
Lactic acid
Malonic acid
Oxalic acid
Propionic acid
Succinic acid
Tartaric acid
Trichloroacetic acid
Materials Required
Sodium carbonate, Na2CO3, or sodium hydroxide solution, NaOH, 3 M
Glass stirring rod
Large glass beaker
pH paper
Overview
Organic acids that are water soluble readily react with bases to form soluble
sodium salts. Some organic acids that have limited solubility in water may produce
soluble sodium salts (e.g., benzoic acid) and are also disposed of by this method.
Sodium hydroxide solutions or sodium bicarbonate are suitable bases. If sodium
bicarbonate is used, carbon dioxide is also formed.
CH3CO2H + NaHCO3 → CH3CO2Na + H2O + CO2
FLINN METHOD #24b continued on next page.
2
The organic acid may be diluted by
adding it slowly to a 20-fold excess of
water while stirring.
H2O
Organic
Acid
3
Neutralize the resulting solution with
sodium carbonate or sodium hydroxide
solution and check the pH of the
final solution with pH paper. Stir the
solution until all solid organic acids
have dissolved.
pH Paper
Na2CO3 or NaOH
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 regulatory
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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