Like iron, and iodine [361], when in a certain state of division, it does not conduct electricity : but, Thus named, because a constituent of alum [(SO,+KO) + (3SO,-A a O,)].

When fused, it is a conductor.

It is ductile.

It does not decom- pose water, at a temperature lower than 212: and, at that point, but slowly.

It dissolves rapidly in acids, and caustic alkalies ; being changed into sesquioxide, and hydrogen, from the decomposed water, being evolved.