While metallic sodium is usually employed as sodium, {HEAD ~ sodium alloys} containing {TAIL ~ a small amount} of other alkali metals or alkaline earth metals may be used so long as their melting points are lower than about 105° C 
containing
While metallic sodium is usually employed as sodium , { HEAD ~ sodium alloys } containing { TAIL ~ a small amount } of other alkali metals or alkaline earth metals may be used so long as their melting points are lower than about 105 ° C
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