> We have found that refractory metals such as molybdenum make excellent propellants, and recycled aluminium alloys can also be used. Exceptions include mercury

> We have found that refractory metals such as molybdenum make excellent propellants, and recycled aluminium alloys can also be used. Exceptions include mercury and gallium, tin, bismuth and lithium (due to their low melting points), cadmium and technetium. Oh darn, I was hoping they'd found a use for all my spare technetium.