Question

What are drying or desiccating agents? Give examples.

Answer 1

Hint: Before answering this question, we must first understand that drying and desiccation are both mass transfer processes. They involve removal of water or any other liquid present by the process of evaporation.

Complete step by step answer:
Drying and desiccating agents are substances that remove water or solvent which are not chemically bound to the compound. They basically just remove humidity which may be responsible for destruction or degradation of a particular product. This is the reason why many products include small packages of silica gel and similar materials inside them. These desiccants are able hold a large percentage of their weight in moisture, and will adsorb the majority of humidity within the package.
These agents are either soluble or insoluble substances that adsorb water due to their chemical properties. Some examples include silica gel, bauxite, anhydrous Calcium chloride and montmorillonite clay.
Desiccants also find use in industrial applications, like humidity detection, waste removal and cleaning, and also regenerative drying.
A drying agent simply absorbs the moisture that is present as an impurity or contaminant with the desired substance. It does not act as a reactant to aids in producing a new substance by a chemical reaction, but simply as a purifier. For example, concentrated sulphuric acid can be used as a drying agent to remove any moisture that is present as impurity with gases.

Note: We must not get confused between desiccating agents and dehydrating agents even though they are both hygroscopic in nature. Unlike desiccating agents, dehydrating agents are reactants and they change the product by removing even chemically combined water molecules.