An unknown blue liquid was boiled. a blue solid was left after the liquid boiled away. is the unknown material a mixture or a pure substance?

i think the unknown liquid is a

It is a mixture. 
take salt water for example if you boil the water the salt will be left behind. salt water on its own is not a pure substance a pure substance would be just the water by its self. 
hope that helps. 

The answer is the pituitary gland. hope this .

The surgical term that means incision into a vein to remove blood or to give blood intravenous fluids is phleb/otomy. hope this !