Generally, when people talk about salt, they think of table salt, sodium chloride, where 40 percent is sodium, and the rest is chlorine. Salts are ionic compounds composed of positive and negative radicals of their respective bases and acids.
When we talk about water and salt together, we only think of it as a solution. Still, interestingly, that is not a certain case every time.
So coming to our question, can salt absorb water? Yes, salts strongly absorb water. Salt compounds and water are polar in nature, so the force of attraction between them is quite strong. Salts that can absorb water are called hygroscopic. Above the 75% relative humidity, salt becomes deliquescent ie; it absorbs so much amount of water that it forms a solution.
Why does Salt Absorb Atmospheric Water?
We all know that salt has a high capacity to absorb water from the environment. Mainly because of salt’s hydrophobic property and having positive and negative charges on it. How?
The chemical components of salt have positive and negative charges, and they attract the opposite charge on atmospheric water.
For eg; in common salt NaCl, Na has a positive and Cl has a negative charge on it whereas in H2O, O atom has a negative charge and H atoms have a positive charge.
Na atom attracts O atom, Cl atom attracts H atom of atmospheric water forming a moisturized salt.
That is the reason why we usually see salt clumps in humid temperatures.
Salt has a special ability to absorb water from the surroundings. Salt can even become deliquescent; it happens when the relative humidity is 75% or above.
Now the question arises what is deliquescent? Salt absorbs so much water into it that it becomes a solution. That’s how salt absorbs water from surroundings!
Do All Salts Absorb The Same Amount Of Water?
No, all salts do not absorb the same amount of water. This amount depends on many factors. For example-
• Structure of the salt
• Polarising power of respective acidic and basic radicals
• How they react with water
How do these factors determine salts absorption of water?
A particular salt can hold a particular amount of water called its water of crystallization. Water is a polar compound that dissolves polar solute in it.
As the structure and geometry decide the dipole moment of salt, its solubility will be affected. The more polar the salt is, the more its reactivity will increase towards the water.
The polarisation of anion and polarising power of cation decides the polarity and structure of the salt because of deformation of the structure by the attraction between the nucleus and electrons of the atoms of elements present in the salt.
Some salts have the property to become a solution after absorbing a specific amount of water. This property is called deliquescence.
How Can Salt Absorb Water if it can be Dissolved in it?
Salt dissolves in enough water!
If the amount of water is not more than that of salt then salt makes bonds to form a hydrate structure ie; salt absorbs water, but if the amount of water is more than that of salt, it can be dissolved to form a salt solution.
This phenomenon completely depends on the relative amount of salt and water. However, we already know how absorption works as the positive ion attracts the negative ion, forming a weak hydrogen bond.
There is a fun fact about salt dissolving in water. Dissolving salt into water is a reversible process that means when water gets evaporated, it will bring the salt back as residue!
How Can Increase in Temperature Affect the Absorption Power of Salt?
An increase in the temperature by heating can dehydrate the salt.
When the temperature increases, the water vapors in the surrounding heat up and rise in the atmosphere making the surroundings less abundant in the water quantity.
Salts may release extra water than before due to osmosis. So a proper temperature is a necessary condition for the absorption of water by the salt.
Does Epsom Salt Absorb Moisture?
Yes, it does. Magnesium sulfate, also known as Epsom salt, is a good absorber of moisture and is even used as a desiccant in its anhydrous form. A desiccant is a substance that can absorb moisture and maintain a state of dryness.
This salt is typically available in its hydrated form. Epsom salt is also used in cosmetics due to its adequate capacity to hold moisture. Epsom salt is an all-rounder and very popular to get used in remedies.
For example, Epsom salt can get used for various purposes-
• Curing wounds
• Muscle and body pain
Can Salt Dehumidify?
Many salts are good moisture absorbers and are used as desiccants and dehumidifiers. Not all salts are good moisture holders, but many salts can dehumidify the surroundings.
People use salts to dry out their houses and surrounding areas in the rainy season.
Salts that are mainly get used as a dehumidifier are-
• Rock Salt
• Table Salt
Using table salt as a dehumidifier is not a good option. Still, it can also be used as a dehumidifier under some circumstances.
However, rock salt is a good dehumidifier. Why? Because it tends to absorb moisture from the surrounding nature. It is the best option to be used as a dehumidifier.
Does Rock Salt Absorb Moisture?
Rock salt is a salt that is mined from the earth’s crust. It is a natural salt that can absorb moisture from the air and can be used as a moisture-holding substance to make its surroundings dry. It is a very popular dehumidifier.
Either in natural or purified form, rock salts can be used to dry out the surroundings as they are effective in both cases.
If you want to get rid of humidity in your house, you should probably go for rock salt! Just get yourself 50-60 pounds of sodium chloride and encounter a miracle. Rock salt is majorly used to naturally get rid of the humidity.
Does Calcium Chloride Absorb Moisture?
Calcium chloride is like a gift from nature. Calcium chloride can effectively absorb moisture around it.
If the temperature conditions are well-suited, it can even absorb water molecules double its weight. This salt is one of the very good absorbers of moisture. It also possesses hygroscopic properties that make it distinctive and a good absorber of moisture from the environment.
The absorption property of calcium chloride gets higher when subsequently the RH rises.
But the question is, how is calcium chloride a very good absorber? Calcium chloride locks the absorbed moisture within a chamber and doesn’t let it escape or evaporate out in the air.
Moreover, calcium chloride is safe for the environment.
How does the acidic or basic nature of salt affect the pH of its aqueous solution?
1. Acidic Salt
Salt can be acidic if the acid involved in salt preparation is strong while the base is weak.
When an acidic salt is dissolved in water, the solution turns acidic, and hence the pH of the solution falls.
This solution can be a good electrolyte as it contains free ions. Acidic salts are ammonium chloride, zinc chloride, and ferric chloride.
2. Basic Salt
Salts can be basic if the basic component is stronger than the acidic component.
These salts can turn their solutions basic, and hence the pH of their solutions may arise.
These solutions can also be good electrolytes. Some examples of basic salts are calcium carbonate, potassium cyanide, and sodium acetate.
How to dry out wet salt?
We face this problem in our day-to-day lives that sometimes salt gets wet, and it’s a real mess. Well, we got a solution!
There are various ways by which you can dry out the wet salt and that too quickly and easily. Let’s have a look at these methods!
1. Mix uncooked dry rice into the salt
well, this remedy is quite old, and we all know how effectively it works.
Just put some uncooked rice into the jar of wet salt and shake it well. Wait for your salt to get dry. When the salt gets dry, remove rice and pour it into a new container.
2. Put a paper tissue into the container of salt
This might work! All you need to do is put a folded paper tissue or towel under the salt container and press it tightly by closing the container.
What will happen? The paper tissue or towel will absorb all the water over time, and your salt will get dry.
3. Coffee beans will help reduce the moisture
Coffee beans are mainly used to dry out the salt. Pour the fresh coffee beans into the container(one-fourth of the container) and leave the salt to get dry. It will absorb all the moisture from it.
Some of the salt can get stuck to the coffee beans, but that’s okay because the remaining salt will be in good condition.
Interesting posts you must read
So far, we’ve discussed salt and how it absorbs water, and to what extent. We’ve seen that different types of salt can absorb different amounts of water. We now know about the difference in facts that salt can absorb water and form a solution in water. How temperature, acidity, and basic nature affect the solution and absorption are detailed.
We usually have many questions about salt and find reasons for what we see around us daily. We learned how different salts can absorb moisture and how useful they are as desiccant and dehumidifiers. Now we can brief about the moisture-holding capacities of calcium chloride, Epsom salt, and rock salt. Therefore, it’s a wrap-up!