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Lithiumaluminiumhydride

If you store it properly, you will have no need to dispose it.

Preliminary notes

  • Lithiumaluminiumhydride which is partially decomposed and thus cannot be used in stoichiometric reactions any more may still be used to dry solvents. If you cannot find a subsequent user please feel free to make a donation to the OC-lab course.
  • It is not true that active lithiumaluminiumhydride must be grey - it may also have a white color.
  • Lithiumaluminiumhydride which seemes to be highly decomposed at the surface may be still very reactive in deeper layers. So do not become careless if at the beginning "nothing happens", if you are going to deactivate the compound.
  • Pellets of lithiumaluminiumhydride are more resistent against decomposition and they are only slightly more expensive than the powder. A second advantage is that the pellets do not form any corrosive dust.

Proper storage helps that the lithiumaluminiumhydride remains active for a long time. Often the compound is delivered in a plastic bag and the bag is soldered in a can. If you open the can and then the bag and after removing the needed quantity you simply plug the bag back into the can then do not be astonished if it needs only days to get the lithiumaluminiumhydride decomposed. If it was you who opened can and bag then it is your job to transfer all of the material into a dry and wide necked vial. Empty the bag onto a sheet of weighing paper first and then transfer from the paper into the vial. Immerse bag and paper completely into water to ensure that there are no residues of active material. Then dispose into the household waste. Wipe the used work space with a moist cloth for the same reason.

Disposing of the pure compound

Dispose lithiumaluminiumhydrid in a separate bottle. Small quantities may also be deactivated. There are several methods of deactivation - all of them with advantages and disadvantages:

  • Put very slowly into water
    Advantage: Water cannot burn. The resulting mixture may be flushed down the drain.
    Disadvantage: The reaction may be very vigorous and therefore has to be carried out very slowly.
  • Put slowly into alcohol
    Advantage: The reaction ist less vigorous than with water.
    Disadvantage: Alcohol is highly flammable. You may run into trouble if you perform the deactivation too careless since the whole mixture may then ignite. Furthermore the final mixture must be disposed as toxic waste.
  • Put slowly into ethyl acetate
    Advantage: Very smooth Reaction
    Disadvantage: It is difficult to detect the end of the reaction (no gas is developed), the mixture must be disposed as toxic waste.

Use water if possible!

Deactivation of reaction mixtures

Since in theses cases organic solvents are still present water is no more suitable, because on the vigorous reaction the mixture may ignite. Deactivate with ethyl acetate or better with alcohol (gas evolution to monitore the reaction). Take care that all of the compound is covered with solvent. Be very careful at the beginning - later on you may speed up the addition of the reagent. Do not be overhasty, but reserve sufficient time instead! The slower the reaction the lower the risk of an accident. If hydrogen gas is developed, draw it of in a pipe into the fume hood's flue.

When the reaction is died down leave the mixture standing alone over night. Next day add water - at the beginning very carefully and again leave the mixture standing alone. Precipitations are dissolved by adding hydrochloric acid.

Cleaning of equipment

Spatulas, flasks, filters, bags (where the compound has been delivered.) - all this is completely immersed in water (no air bubbles!) to decompose all adherent residues. Wipe used work areas or balances with a moist cellulose sheet.