Posted by Dave on .
I was not the person who wrote that question last night?
Chemistry - DrBob222, Wednesday, November 15, 2006 at 7:24pm
Yes, it is possible in some cases. For example, CoCl2 is blue in the unhydrated form and pink in the hydrated form. As a kid, I used a water color brush to "paint" a solution of CoCl2 onto a fish from a coloring book. I hung the painted finsh outside. The fish was blue when the humidity was low; it was pink when the humidity was high. I hope this helps.