Drying agents are used to remove excess water from organic solvents. Even though organic solvents may be insoluble in water, due to their polarity they may attach to some water molecules. This water has to be removed to attain high-purity organic compounds, however their removal by water evaporation may not be possible due to similar boiling points of organic compounds. In such cases, chemicals are used to remove this water.
Drying agents are characterized by Capacity, Efficiency and Velocity. The capacity refers to the maximum number of water molecules that drying agents can bind. Efficiency refers to the amount of water left in the organic solution after the completion of drying process. Velocity refers to the speed of drying, in other words, how fast can a drying agent remove water.
Some examples of drying agents are calcium chloride, calcium hydride, sodium metal, sodium sulfate, magnesium sulfate, etc.
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