Hello, I am instructed by my chemistry professor to design an experiment to measure the temperature at which a saturated solution of Sodium Nitrate will begin to boil. If the reagents are pure this temperature will be constant . Can someone tell me why does the lab instructor suggests that the thermometer be placed on the surface of the liquid and not completely inserted in it. (IE he advises that it is essential to place the bulb, half immersed and the other half not immersed in the solution). Is this necessary ? Why ?