Question

Briefly describe the two major techniques gravity filtration and vacuum filtration that were utilized in this experiment, and discuss why you would choose one method over the other. (Note: my experiment was isolation of the active ingredient in analgesic tablet)

Answer 1

Vacuum filtration is a chemistry laboratory technique which allows for a greater rate of filtration. Whereas in normal filtration gravity provides the force which draws the liquid through the filter paper, in vacuum filtration a pressure gradient performs this function. This has the advantage of offering a variable rate depending on the strength of the pump being used to extract air from the Büchner flask. Care must be taken not to use such a strong vacuum that the filter paper rips.

vacuum filtration is usually faster than a simple gravity filtration using a simple conical funnel. However, there are several points that have to be considered when performing a vacuum filtration. Due to the fact that reduced pressure is used in this procedure, special attention has to be paid to the equipment used in this procedure. The glassware (i.e. filter flask) should not have any cracks on the sides or the bottom. It is also imperative that the filter flask and the vacuum trap are clamped securely, so that they do not move during the filtration. The thick-walled tubing tends to act like a whip sometimes, and slams the filter flask into the hotplate or other metal objects resulting in an implosion.