Handling and weighing solids under inert atmosphere

5 Handling and weighing solids under inert atmosphere 

As usual, plan your work ahead and make sure you have a flask pre-dried and under inert gas. The metal will normally be under paraffin oil and may also have an oxide or hydroxide layer coating it. Both these impurities will have to be removed before weighing the metal and this can be done using the following sequence (Fig. 6.17). Remember that some reactive metals are pyrophoric when they come into contact with moisture. 

Place the metal into a beaker, covering it with oil, then cut some of it into small pieces with a scalpel, removing any coating and leaving the shiny surface exposed. Heavily coated potassium has been known to detonate on cutting and should be discarded. 

Using a pair of forceps, quickly wash the oil from the metal chunks in a second beaker containing dry hexane or pentane. Remove the chunks, allowing the solvent to evaporate very briefly, and drop into a weighed beaker of oil. 

Once you have weighed the required quantity, remove the metal chunks, wash again in the petroleum ether, quickly add them to the reaction flask and re-connect to the inert gas system. 

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