The key difference between desiccant and deliquescent is that the term desiccant describes substances that are hygroscopic, but the term deliquescent refers to the ability to absorb moisture and become liquid.
The term desiccant refers to a particular substance that can be used to remove moisture from a particular environment. It is used as a noun to name a compound. The term deliquescent describes a property of a particular substance, and it is used as an adjective to describe a substance.
CONTENTS
1. Overview and Key Difference
2. What is Desiccant
3. What is Deliquescent
4. Side by Side Comparison – Desiccant vs Deliquescent in Tabular Form
5. Summary
What is Desiccant?
A desiccant is a substance that can absorb water vapour from the external environment. And, this term is used to refer to “hygroscopic substances’. Hygroscopic substances are solids that can absorb or adsorb water from its surroundings. When water vapour is absorbed by hygroscopic substances, the water molecules are taken into the spaces of the crystal structure. It causes the volume of the substance to increase. Hygroscopy can result in changes in the physical properties of the hygroscopic substances; such properties include colour, boiling point, viscosity, etc.
Figure 01: Zinc Chloride is a Desiccant
Most examples of hygroscopic substances include salts. Some examples are Zinc chloride (ZnCl2), sodium chloride (NaCl) and sodium hydroxide (NaOH). There are also some other common substances we know as hygroscopic. These compounds include honey, silica gel, germinating seeds, etc.
What is Deliquescent?
The term deliquescent refers to the ability of a substance to absorb moisture from the environment and dissolve itself. Therefore, deliquescent substances are solid matter that can get dissolved by absorbing water vapour. The resulting solution is an aqueous solution. And, this process is known as deliquescence. These deliquescent substances have a high affinity for water.
The atmosphere has 0-4% of water vapour, depending on the location and time of the day. Since there are many other gases and vapours in the atmosphere, water vapour has a partial pressure. Deliquescence happens when the vapour pressure of the solution that is going to form is less than the partial pressure of water vapour in the air.
Figure 02: Calcium Chloride is a Deliquescent Compound
Humid environments are highly concentrated with water vapour. Therefore, deliquescent substances can easily undergo deliquescence and form solutions by absorbing a high amount of water vapour when they are placed in a humid environment.
Most common examples of deliquescent substances include some salts; for example, sodium hydroxide, potassium hydroxide, ammonium chloride, sodium nitrate, calcium chloride, etc. These substances can be used as desiccants. When the water vapour inside a container has to be removed in order to stop a particular chemical reaction, these substances can be kept inside the container. Then, the deliquescent substances will absorb a high amount of water and prevent the interferences coming from water vapour.
What is the Difference Between Desiccant and Deliquescent?
A desiccant is a noun used to name a compound. The term deliquescent is an adjective we can use to describe a compound. The key difference between desiccant and deliquescent is that the term desiccant describes the substances that are hygroscopic, but the term deliquescent refers to the ability to absorb moisture and become liquid.
Below infographic tabulates the differences between desiccant and deliquescent.
Summary – Desiccant vs Deliquescent
A desiccant is a noun used to name a compound. The term deliquescent is an adjective that we can use to describe a compound. The key difference between desiccant and deliquescent is that the term desiccant describes the substances that are hygroscopic, whereas the term deliquescent refers to the ability to absorb moisture and become liquid.
Reference:
1. Helmenstine, Anne Marie. “Desiccant Definition in Chemistry.” ThoughtCo, Feb. 11, 2020, Available here.
2. Helmenstine, Anne Marie. “Deliquescence Definition.” ThoughtCo, Feb. 11, 2020, Available here.
Image Courtesy:
1. “Zinc chloride” By User:Walkerma – Own work, Public Domain) via Commons Wikimedia
2. “Calcium chloride CaCl2” By Firetwister assumed – No machine-readable source provided. Own work assumed (based on copyright claims) (CC BY-SA 3.0) via Commons Wikimedia