Question: what is the primary purpose of using sand in the still pot heating bath

title: Reflux
text: The apparatus shown in the diagram represents a batch distillation as opposed to a continuous distillation . The liquid feed mixture to be distilled is placed into the round - bottomed flask along with a few anti-bumping granules , and the fractionating column is fitted into the top . As the mixture is heated and boils , vapor rises up the column . The vapor condenses on the glass platforms ( known as plates or trays ) inside the column and runs back down into the liquid below , thereby refluxing the upflowing distillate vapor . The hottest tray is at the bottom of the column and the coolest tray is at the top . At steady state conditions , the vapor and liquid on each tray is at equilibrium . Only the most volatile of the vapors stays in gaseous form all the way to the top . The vapor at the top of the column then passes into the condenser , where it cools until it condenses into a liquid . The separation can be enhanced with the addition of more trays ( to a practical limitation of heat , flow , etc . ) . The process continues until all the most volatile components in the liquid feed boil out of the mixture . This point can be recognized by the rise in temperature shown on the thermometer . For continuous distillation , the feed mixture enters in the middle of the column .