Page 257 - Demo

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Flinn Method #24b, continued Procedure
1
Perform this procedure in a fume hood. Wear chemical splash goggles, chemical-resistant gloves and a lab coat or chemical-resistant apron.
Chemical Disposal Procedures
255
FLINN METHOD
2
Perform this proce- dure in a fume hood. Wear chemical splash goggles, chemical- resistant gloves and a lab coat or chemical- resistant apron.
3
H2O
Inorganic Acid
1 M Na2CO3
Calcium carbide reacts with water to generate acetylene, a highly flam- mable gas. Leftover calcium carbide in an experimental procedure may be decomposed with water.
Example
Calcium carbide
Materials Required
Large glass beaker 3⁄4 full of water Glass stirring rod
Dry chemical (ABC) fire extinguisher Hydrochloric acid, HCl, 3 M
pH paper
Overview
Calcium carbide reacts with water to form acetylene gas and calcium hydroxide, which is not very soluble in water. The addition of hydro- chloric acid to the suspension of calcium hydroxide will dissolve it, forming water and calcium chloride. The resulting mixture should be neutralized if needed prior to drain disposal.
CaC2 + 2H2O → C2H2 + Ca(OH)2 Ca(OH)2 + 2HCl → CaCl2 + 2H2O
Procedure
1
Perform this procedure in a fume hood. Wear chemical splash goggles, chemical-resistant gloves, and a lab coat or chemical-resistant apron.
2
This procedure is
intended for small
amounts (<10 g)
only! Carbides react
with water, so keep
these materials dry
until ready for use or
disposal. Slowly put
the carbide granules H2O into a large beaker of
water with stirring.
Flammable acetylene
gas will be given off.
Allow the acetylene
to dissipate in the air
but avoid sources of possible ignition in the area. Allow the mixture to stand for several hours. The resulting solution will be strongly basic.
#25 Carbides
Slowly add 1 M
sodium carbon-
ate solution to the
diluted acid while
stirring. Carbon
dioxide gas will
be evolved. As
the acid is neutral-
ized by the sodium
carbonate, the rate of gas evolution will decrease. When further additions of sodium carbonate solution yield no gas evolution, the neutralization is complete.
4
Rinse the neutral mixture down the drain with a 20-fold excess of water.
CO2
Solid Carbide
pH Paper
Flinn Suggested Laboratory Chemical Disposal Methods
Flinn Scientific has been publishing suggested laboratory chemi- cal disposal methods for more than 40 years. Each chemical in the Flinn Scientific Catalog/Reference Manual has a disposal number under its name. The disposal number refers to one of the suggested disposal procedures listed in this section. As federal, state, and local regulations have changed, some of the disposal procedures have been updated or deleted. Before attempting any disposal procedures, it is essential that you check local regula- tions to determine if it is still allowed in your locale.
If you have any questions concerning laboratory waste disposal methods, please call (800-452-1261) or e-mail (flinn@flinnsci. com).
3
Using pH paper to monitor pH, neutralize the solution with 3 M hydrochloric acid.
4
3M HCI
Decant the neutral solution and rinse it down the drain with a 20-fold excess of water.
5
Dry any remaining solid and package it for disposal in a landfill suit- able for chemical wastes.