Abstract
The use of sodium in chemical research is hampered by its reactivity in moist air, which leads to difficult handling and measurement methods. We describe a simple method using disposable microcapillary pipettes for small quantity applications. Using the proper precautions, glass micropipettes are sealed on one end and loaded, open end down, in a test tube. Sodium is cleaned and loaded into the test tube under a stream of inert gas. The test tube is closed with a three way stopcock and flushed with inert gas. The test tube is evacuated to 20 mbar using a standard vacuum pump (not a water vacuum) and the sodium is melted using a heat gun (mp=97.8 oC). After liquefaction, inert gas is injected, bringing the pressure in the test tube to atmosphere. This pressure increase causes the clean liquid sodium to fill the micropipette. The oxidized sodium remains in the test tube, which can now be opened and the micropipettes removed. The sodium on the outside of the micropipettes can now be cleaned and the extra sodium treated with isopropanol. The solid sodium in the micropipette can now be utilized in the quantity desired (density = 0.97 g/mL) by fracturing the measured length of pipette necessary using the magnet-hammer method or by sublimation, using proper protection methods.
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