APPENDIX 3

METHODS FOR DESTROYING SMALL QUANTITIES

OF SOME COMMON REACTIVE MATERIALS*

Alkali metals

Li/Na A safe method for the disposal of small quantities of sodium metal is the careful addition of small amounts of sodium metal to a beaker containing 2‑propanol in a fume hood. Some water (up to 2%) may be added to the reaction. CAUTION: hydrogen gas is evolved. As reaction proceeds, the 2-propanol will increase in temperature thus increasing the reaction rate.

K Perform the following procedure carefully in a fumehood. Potassium is substantially more reactive than lithium or sodium. Equip a dry 3‑necked round bottom flask with nitrogen and place the potassium in it. Add carefully 21 mL of tert‑butyl alcohol per gram of potassium at such a rate that rapid refluxing occurs. Stirring is started as soon as enough t‑butyl alcohol has been added. The mixture is stirred and heated under reflux until all of the potassium has dissolved. The heat is turned off. When you are positive all of the potassium has been consumed, add an equal volume of water at a rate that causes gentle refluxing. The solution is cooled, neutralized and disposed of as non-halogenated organic waste.

Metal Hydrides

LiAlH₄ In the fume hood behind a shield, cautiously and slowly carry out the following procedure. The stirred reaction mixture from n grams of lithium aluminum hydride (or a mixture of n grams LiAlH₄ in 20n to 5On mL of dry ether) is treated by successive dropwise addition of (1) n mL of H₂O, then (2) n mL of 15% sodium hydroxide solution and finally (3) 3n mL of H₂O. Most of the vigorous reaction occurs during the first addition of water. CAUTION: hydrogen gas is evolved. This procedure gives a granular precipitate which is removed easily by filtration and treated as normal solid waste. Discard the filtrate as organic waste. Note: this method of destroying excess LiAlH₄ is good for working‑up LiAlH₄ reduction reactions.

NaBH₄ In the fume hood, cautiously add small portions of sodium borohydride to a large volume of water such that the concentration of borohydride is less than 3%. Under a nitrogen atmosphere, add dilute acetic acid dropwise with stirring. When neutralization is complete, dispose of as non-halogenated organic waste.

Lewis Acids

BF₃-Et₂O Wear rubber gloves and eye protection. In the fume hood pour the boron trifluoride complex into a large evaporating dish. Cautiously cover the boron trifluoride complex with excess solid soda ash or calcium carbonate. When the reaction has subsided, very slowly add the mixture to a pail of cold water. Allow to stand 24 hours. Test the pH of the solution and neutralize if necessary. Remove waste to the waste disposal facility.

TiCl₄ Wear rubber gloves and goggles or a face shield. Add the titanium tetrachloride (10 mL) dropwise from a dropping funnel to a stirred 5% solution of sodium hydroxide (250 mL) cooled in an ice bath. Filter the solid and treat as normal refuse. Remove waste to the waste disposal facility.

SnCl₄ In the fume hood, cautiously and slowly add to a large container of water. Slowly stir in soda ash until the solution is neutral to litmus and a thick, white precipitate has formed. Let stand for 24 hours. Decant the liquid to the drain with a large volume of water. Remove waste to the waste disposal facility.

*Detailed procedures for the disposal (and decomposition, if necessary) of a large number of compounds is contained in "Hazardous Chemicals: Information and Disposal Guide" by M.A. Armour, L.M. Browne, G.L. Weir, University of Alberta, (3rd edition, 1987). There is a copy of this book in each research laboratory in the Chemistry department.