flinnsci.com SAFETY REFERENCE CHEMICAL DISPOSAL PROCEDURES
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1
Perform this procedure in a fume hood. Wear chemical splash goggles, chemicalresistant
gloves and a lab coat or chemical-resistant apron.
Flinn Method #12b, continued
FLINN METHOD
#13 Organic Sulfides, Mercaptans and Thioamides
Organic sulfides and mercaptans are toxic and should not be drain disposed.
Because of their toxicity, they should only be disposed of by a licensed hazardous
waste disposal company as described in Flinn Disposal Method #26c.
FLINN METHOD
#14 Cyanides and Solid Metal Cyanide Complexes
All cyanides must be removed by licensed hazardous waste disposal. Cyanides
are severe and rapid-acting poisons, being quickly absorbed into the body via
the respiratory system, skin, eyes and mouth. Cyanides are identified as acutely
hazardous, P-listed wastes by the EPA. They are also classified by the Resource
Conservation and Recovery Act (RCRA) as characteristic hazardous wastes due to
their reactivity with water to produce toxic hydrogen cyanide gas.
Compounds containing metal cyanide complex ions, such as potassium
ferrocyanide or potassium ferricyanide, are generally considered nontoxic and
are much less reactive than simple cyanide salts. Complex iron cyanides may
generate hydrogen cyanide in contact with concentrated hydrochloric acid or when
heated. Nevertheless, both potassium ferrocyanide and potassium ferricyanide are
classified as P-listed wastes.
The following detoxification procedure using bleach only may be applied to
leftover solutions containing ferri- or ferrocyanide ions as part of an experimental
procedure. The detoxification procedure may NOT be used to treat any cyanidecontaining
hazardous waste.
Examples
Potassium ferrocyanide, potassium ferricyanide
Materials Required
Calcium hypochlorite solution, Ca(OCl)2, 30%
Sodium hydroxide solution, NaOH, 3 M (twofold molar excess)
Sodium hypochlorite solution (bleach)
Glass stirring rod
Ice bath (optional)
Large glass beaker
pH paper
Overview
Ferro- and ferricyanides are much less toxic than cyanide salts and are oxidized
to cyanates by hypochlorite. A 50% molar excess of bleach is required to assure
complete destruction.
CN¯ + OCl¯ → OCN¯ + Cl¯
Commercial bleach (5.25% sodium hypochlorite) or a 30% calcium hypochlorite
solution can be used for this procedure.
Procedure B: Nitrites
1b
Perform this reaction in a fume hood. Wear chemical splash goggles, chemicalresistant
gloves and a lab coat or chemical-resistant apron.
5b
Check the pH of the solution and neutralize to pH 5–10. Rinse the solution down the
drain with excess water.
Procedure
pH Paper
FLINN METHOD #14 continued on next page.
2b
Dissolve the inorganic nitrite salt in
distilled water.
H2O
3b
Add a 50% molar excess of ammonium
hydroxide solution.
NH4OH
4b
Using pH paper to monitor the process,
acidify the solution to pH 1 with 3 M
hydrochloric acid. Stir for two hours.
3 M
HCl
pH Paper
2
Fill a large beaker 1⁄2 full of water and,
using pH paper, make it basic (at
least pH 12) by adding 3 M sodium
hydroxide solution, as needed.
3 M NaOH
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