Re: Why does cobalt chloride change color??

Ken,

Interesting question as it involves both the familiar color change (we see 
it in self-indicating desiccants like silica-gel) AND a not so 
familiar change of state (solid - liquid - solid).


I presume that your starting material is the hydrated cobalt chloride, 
that is CoCl2.6H2O.  This is a red/pink color.
  
When heated to 86 degC, this hexahydrate melts.  It is actually 
dissolving in its own "waters of crystallization".  This is still 
red.
  
At 110 degC, this water is lost as the solution boils.  A blue solid, 
anhydrous CoCl2 remains.

Do not heat to decomposition since toxic chlorine and cobalt fumes are 
formed.

See 
Material Safety Data Sheet
for safety information!

Thanks for your question.