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Sodium metal reacts with water and is thus typically stored under mineral oil or kerosene.
Preparation of Sodium Metal for synthesis
Sodium metal is often used as a strong base to prepare sodium derived salts. It is also used in Birch reductions. Because it is typically stored under oil, the oil must typically be removed.
- Obtain a bucket of sand, LithX powder or a class D fire extinguisher. You should be wearing gloves, eye protection and a labcoat.
- Remove the sodium metal from the container, allowing the excess oil to fall back into the jar
- Cut the sodium to approximately the appropriate size while there is still a small amount of oil remaining on the metal. You will notice that shortly after the metal is cut, it turns from a bright metallic color to a dull white color. This is normal.
- Place any unneeded sodium back in the oil.
- The sodium you wish to weigh out should be patted dry with paper towels to remove excess oil. It can be rinsed with hexanes over the towels.
- Weigh out the appropriate amount of sodium by gently cutting unneeded pieces from the block.
- Add sodium metal to your reaction.
Alternatively, the sodium metal can be removed from the container, and placed into a beaker of an alkane solvent such as hexane or heptane. The sodium can be cut into appropriate sized pieces with tweezers and a scalpel while immersed in the solvent, minimising air exposure. This technique can also be used to handle other alkali metals such as lithium and potassium.
Safety and Hazards
Sodium metal is flammable and exothermically generates hydrogen gas which can spontaneously light on fire in the presence of acids and water. Larger blocks of sodium metal, however, only slowly react and form a layer of inert oxides and hydroxides on the surface which render the outer surface largely inert from atmospheric moisture.
Sodium metal can safely be handled with gloves for short periods of time out in the open without fear of fire. Finely powdered sodium metal should never be handled in the open as exposure to moisture will both reduce the quality of the reagent as well as potentially cause large fires which are difficult to extinguish.
If there is a fire, DO NOT attempt to extinguish it with water. DO NOT attempt to extinguish it with a normal fire extinguisher - as this will propagate the flaming material across the room by blasting it with pressurized carbon dioxide. To extinguish a metal fire, it is ideal to either use an appropriate Metal "Class D" fire extinguisher or to pour large quantities of SAND over the fire.
Sodium Metal can be quenched by addition of organic protic solvents, usually highly branched ones such as tert-butanol are used as they react slowest. Avoid quenching with water as this may result in an explosive fire.
Contributors
- Kiwi, Kyle
