Question

Post-lab Filtration experiment questions. 1. If your goal is to separate oil from sand, estimate how much of oil and how much of the sand do you lose during the vacuum filtration experiment. 2. How would you modify the experiment procedure, if I would give you a mixture on unknown amount of oil and sand and would ask to calculate the weight percentage of sand in the mixture?

Answer 1

Questions 1 and 2.

Suction filtration (vacuum filtration) is the standard technique used for separating a solid-liquid mixture when the goal is to retain the solid (for example in crystallization). Similar to gravity filtration, a solid-liquid mixture is poured onto a filter paper, with the main difference being that the process is aided by suction beneath the funnel

Advantages: Suction filtration is much faster than gravity filtration, often taking less than one minute with good seals and a good vacuum source. Suction filtration is more efficient at removing residual liquid, leading to a purer solid. This is especially important in crystallization, as the liquid may contain soluble impurities which could adsorb back onto the solid surface when the solvent evaporates.

Disadvantages: The force of suction may draw fine crystals through the filter paper pores, leading to a quantity of material that cannot be recovered from the filter paper, and possibly an additional quantity that is lost in the filtrate. This method, therefore, works best with large crystals. On small scales, the loss of material to the filter paper and filtrate is significant, and so other methods are recommended for microscale work.