Question

When blue ink is heated,what do you think has got evaporated from the watch glass/

Answer 1

This is a experiment of separating dye from ink : Fill half a beaker with water and put a watch glass on the mouth of the beaker . Put few drops of ink on the watch glass. Now start heating the solution or mixture. after that the water evaporate continue heating till there is no further change in the watch glass . When the water is completely evaporated from the watch glass Dye is left in the watch glass