Page 256 - Demo

Safety Reference
Flinn Method #23, continued 4
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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 chlo- ride 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.
#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 neutral- ized 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
Large glass beaker
Glass stirring rod
Sodium carbonate, Na2CO3, or sodium hydroxide solution,
NaOH, 3 M pH paper
Overview
Procedure
1
Perform this procedure in a fume hood. Wear chemical splash goggles, chemical-resistant gloves and a lab coat or chemical-resistant apron.
FLINN METHOD
2
The organic acid may be diluted by adding it slowly to a 20-fold excess of water while stirring.
3
Neutralize the resulting solu- tion with sodium carbonate or sodium hydroxide solu- tion and check the pH of the final solution with pH paper. Stir the solution until all solid organic acids have dissolved.
4
H2O
Acid
pH Paper
Na2CO3 or NaOH
Adjust the pH of the mixture to 5–9, if needed, and rinse the solution down the drain with an excess of water.
#24b Acids,Inorganic
Neutralization of acid and base solutions (corrosive wastes) is a gener- ally 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
Large borosilicate glass beaker less than 1⁄2 full of water Glass stirring rod
Sodium carbonate solution, Na2CO3, 1 M
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 #24b continued on next page.
Organic
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
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.