Refluxing is all over this book and the proper apparatus to use is pictured in figure 7a. The most general thing that can be said
about refluxing is that it's just plain old boiling except that there is a condenser attached to the flask so that nothing escapes. The condenser must be supplied with really cold water, especially when refluxing high boiling solutions.
You see that vacuum adapter stuck to the top of the condenser in fig. 7a? Well, a closer look at it in fig. 7b will show that it has some drying agent sandwiched between two cotton balls and the nipple (tee heel) sealed with plastic wrap or foil. The drying agent can be either a commercial product called Drierite or calcium chloride. This attachment is placed on top of a condenser when refluxing solutions that have no water in them and must remain that way during the time they are refluxed. All this is to prevent moisture in the outside air from coming into contact with the cold surface of the of the inside walls of the condenser. This will surely happen and the condensed outside-air water will drip down into the reaction flask and ruin the experiment. This is not so much a concern when refluxing large aqueous solutions such as acid or base hydrolysis seen later in this book.
One side note about the drying attachment is that it need not be a vacuum adapter. Anything, such as a funnel, that can hold a plug of drying material and fit snugly into the condenser will work.
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