Dhristi JEE 2022-24

What is Soda Lime?

Soda-lime is a white to grayish-white colored crystalline solid, which is a mixture of Calcium oxide and Sodium or Potassium hydroxide (both corrosive substances). Soda-lime is noncombustible and miscible in water with a release of heat, i.e., an exothermic reaction takes place. It is corrosive to both tissue and metals. This page discusses the soda-lime, soda-lime formula, soda-lime formula equation, soda-lime molecular formula, soda-lime composition, the function of soda-lime with its properties in detail.

Soda Lime Definition

Soda-lime is a soft drink lime. It is a combination of NaOH and CaO synthetics, utilized in granular structure in closed breathing conditions, like general sedation, submarines, rebreathers, and recompression chambers, to eliminate carbon dioxide from breathing gases to prevent \[CO_{2}\] maintenance and carbon dioxide harming. 

Soda-lime is a granular solid created by slackening quicklime (CaO) with a concentrated arrangement of sodium hydroxide, NaOH(aq). In substance reactions, Soda-lime does act as sodium hydroxide yet, in contrast to sodium hydroxide, it isn't deliquescent and doesn't attack the glass.

Soda-lime reacts with \[CO_{2}\] being breathed out by the creatures in the soil. The change in the weight of the soda-lime over the 48-hour hatching period can be utilized to estimate the amount of \[CO_{2}\] breathed by the soil microorganisms and different living beings. The size of soda-lime granules is significant. On the off chance that granules are too huge, the surface area of absorption is insufficient; on the off chance that they are too little, the tight space between granules brings about a high protection to breathing.

Soda Lime Chemical Formula

Soda lime's molecular formula is \[CaHNaO_{2}\].

Soda Lime Composition

The chemical components included in the Soda Lime formation are Calcium oxide, CaO (about 75%)Water, \[H_{2}O\] (about 20%)Sodium hydroxide, NaOH (about 3%)Potassium hydroxide, KOH (about 1%).

Properties of Soda Lime

Soda Lime Float Glass Properties: Soda Lime Glass, otherwise called Float Glass contains both sodium and calcium and is formed by drawing the glass over liquid tin showers. 

Thermal and Mechanical Properties

  • Thermal Conductivity: 0.937 W/mKDensity (at 20 °C/68 °F): \[2.44 g/cm^{3}\]

  • Hardness (Mohs Scale): 6 - 7Knoop 

  • Hardness: \[585 kg/mm^{2}+ 20\]

  • Modulus of Elasticity (Young's): \[7.2 x 10^{10}Pa\]

  • Modulus of Rigidity (Shear): \[3.0 x 10^{10}Pa\]

  • Bulk Modulus:\[4.3 x 10^{10}Pa\]

  • Poisson's Ratio: 0.22

  • Specific Gravity: 2.53

  • Specific Heat: 0.21

  • Specific Weight: \[2,483 g/cm^{3}\]

  • Thermal Coefficient of Expansion is 0/300 °Ca: 8.6 x 10 -6/°C

  • Softening Point: 726°C/1340°F

  • Annealing Range: 546°C/1015°F

  • Strain Point: 514°C/957°F

Soda Lime Formula

Soft drink lime doesn't have a substance recipe since it is a combination of synthetic compounds. It's made out of;- ~ 75% Calcium Hydroxide \[Ca(OH)_{2}\] ~ 20% Water \[H_{2}O \] ~ 5% Sodium Hydroxide (NaOH). Soft drink lime is set up by blending powdered slaked lime in with a fine fog of 20% sodium hydroxide arrangement in a rotating blender to shape permeable, round granules which are then dried. The time taken fluctuates on the interaction, yet generally, a group can be set up in 1 - 2 hours.

It's utilized for retention of \[CO_{2}\] in both the substance research center and mechanical applications, for example, shut breathing conditions for example submarines, SCUBA re-breathing contraption, decompression chambers, hyperbaric chambers, and so forth.

Soda Lime Formula Equation

The fundamental overall reaction of \[CO_{2}\] absorption with soda lime is as per the following;- 

\[Ca(OH)_{2} + CO_{2} \rightarrow  CaCO_{3} + H_{2}O \]

This reaction is generally delayed all alone, which is the reason the 'pop' part (sodium hydroxide) is added. NaOH act as a catalyst to work with a quicker by and large reaction:

\[CO_{2} + NaOH \rightarrow  NaHCO_{3}...(1) \]

Now,  \[NaHCO_{3}\] reacts further with slaked lime to form caustic soda. 

Further Reaction:  

\[NaHCO_{3} + Ca(OH)_{2} \rightarrow  CaCO_{3} + H_{2}O + NaOH ...(2) \]                          

(Baking soda)    (Slaked lime)   (Limestone)     (Water)     (Caustic soda)    

The development of water in the last response additionally accelerates the assimilation of \[CO_{2}\] by going about as a dissolvable to disintegrate \[CO_{2}\] and make it more accessible for the main response with sodium hydroxide.

Functions of Soda Lime

Soda-lime is utilized in breathing systems to absorb expired \[CO_{2}\] during anesthesia/insensibility.

It can be unified in a Mapleson C system or a circle system.

The Reaction:

\[ H_{2}O + CO_{2} \Rightarrow H_{2}CO_{3} high pH \]

\[ H_{2}CO_{3} + 2 NaOH \Rightarrow Na_{2}CO_{3} + 2H_{2}O high pH \]

\[ Na_{2}CO_{3} + Ca(OH)_{2} \Rightarrow CaCO_{3} + 2 NaOH high pH \]

\[ H_{2}CO_{3} + Ca(OH)_{2} \Rightarrow  CaCO_{3} + 2H_{2}O high pH \]

Point to Note: Reaction 4 happens just at a lethargic rate in these absorbents. \[CO_{2}\] in solution reacts with sodium hydroxide to frame the separate carbonates, which at that point react with calcium hydroxide to create calcium carbonate, recharging sodium hydroxide. Heat and water are released during the reaction. Fatigue of its action is demonstrated by colours; the most well-known one changes from pink to white.


Soda-lime is the common name for Sodium calcium hydrate (\[CaHNaO_{2}\]). It gets its name from two of its constituents sodium (Na) and limestone \[(CaCO_{3})\].

Physical Form

It is in the form of small whitish crystals which are easily breakable if managed strongly. They are brittle. Hence they are needed to handle carefully. 

Soda-lime has a great number of properties based on its constituents and their ratio. The differing ratios led to its usage in laboratories, hospitals, nursing homes, industries, and disaster management. 

Properties of Soda Lime

  1. It is a mixture of sodium and calcium oxides and hydroxides in multiple ratios. Sometimes potassium hydroxide is also used to make soda lime. However, it is less common. Hence there can be many formulas. One such example, students can find here.

  2. Highly corrosive and reactive. Hence can not be kept open. It should be kept away from the reach of children. And if used in the laboratory then one must wear protective gear.

  3.  It has high absorption properties. It can easily absorb Carbon dioxide. 100 grams of soda-lime can absorb about 20 liters of \[CO_{2}\]. First, \[CO_{2}\] reacts with water present in soda-lime forming carbonic acid and then this acid reacts with strong bases to form carbonate and bicarbonate salts.

  4. It is soluble in water. Water deneutralizes its effectiveness by diluting it.    

  5. It is highly corrosive. It reacts rapidly with metals corroding them.

  6. It is non-combustible on its own but starts decomposing on heating producing toxic fumes. 

  7. It is highly alkaline. The pH is greater than 13. This is because it contains strong basic hydroxides of calcium and oxide of sodium. It turns litmus blue.  

  8. It causes decarboxylation. In the case of salicylic acid, it converts acid into phenol while it converts benzoic acid into benzene. 


Uses of Soda Lime 

  1. It is used for the laboratory preparation of methane gas. It is reacted with anhydrous sodium acetate, releasing methane gas as a product.

  2. It is used for checking the presence of nitrogen in organic compounds. A small amount of compound is heated with soda lime. If there is the liberation of foul-smelling ammonia gas, it indicates the presence of nitrogen compounds. However azo compounds do not give this test. Azo compounds are described here. It is used to make soda-lime glass. Silica is added to soda lime to provide stability and hardness. This glass is stable and used in various items.

  3. It is also used in removing toxic gases like arsenic if they get leaked into laboratories. They are also used in masks to absorb toxic gases.

  4. It is also used in water treatment plants to remove hardness. Calcium and sodium salts bind with magnesium and potassium present in the water into an insoluble substance, which is later filtered out. The process is called the soda-lime or lime-soda process. 

  5. It is also used as a drying agent in hospitals, pathologies, and laboratories.

To know more about soda-lime and its various properties, log on to Vedantu and find out what the experts have to say. Get the factual information of this chemical compound and learn what it is to answer questions during exams.

FAQs on Soda Lime

1. Differentiate Between Lime and Soda Lime.

Lime Water Versus Soda Lime:

  1. Lime water is a dilute solution (water-added) of calcium hydroxide, Ca(OH)2, in water.

  2. Soda lime is a mixture of sodium hydroxide, NaOH, known as caustic soda, and calcium oxide or CaO, also known as quicklime.

  3. Lime is citrus and is good for health, while soda lime is lime mixed with soda, soda is not good for health, as it affects your kidneys and liver.

2. What is the difference between the Cold Lime Soda Process and the Hot Lime Soda Processes?

Below is the list of processes taking under the Cold Lime Soda Process and Hot Lime Soda Process.

Cold Lime Soda Processes:

  • It is done at room temperature. 

  • Reactions occur at a moderate rate. 

  • The precipitations formed are exceptionally fine so the utilization of coagulants is fundamental. 

  • Filtration of the accelerated form is troublesome. 

  • Dissolved gases are not eliminated.

Hot Lime Soda Processes: 

  • It is completed at a raised temperature of around 100℃. 

  • Reactions happen at a quick rate. 

  • Coagulants are not needed. 

  • Filtration is simple and quicker at higher temperatures. 

  • Dissolved gases, for example, CO2  are eliminated.

3. What is Ca(OH)2?

Calcium hydroxide, usually alluded to as slaked lime, is portrayed by the compound recipe Ca(OH)2. It is an inorganic compound that has a white, fine appearance in its strong state. It has a dull appearance in its crystalline structure. 

The substitute names of this compound: hydrated lime, slack lime, pickling lime, and caustic lime. Usually, calcium hydroxide is prepared by blending water and calcium oxide (otherwise called quick lime). 

The synthetic response between sodium hydroxide and calcium chloride disintegrated in water (liquid CaCl2) additionally yields Ca(OH)2.

4. Can we eat soda lime?

No, we cannot eat soda lime. Soda-lime is a highly corrosive and strongly alkaline salt.  It can affect the gastrointestinal tract when engulfed and can cause the death of the person. One should not touch soda-lime crystals with bare hands because it will cause severe skin burns.

5. Why does soda-lime have higher reactivity than calcium hydroxide alone?

Soda-lime has sodium hydroxide(NaOH) along with calcium oxide (CaO) as a constituent. NaOH is a strong base hence it leads to the higher reactivity of soda lime.

6. Which type of compound soda lime is it? 

Soda-lime is a mixture of sodium, potassium, and calcium salts. It cannot be called a compound. It does not have the exact ratio of the elements which is important for compounds.

7. Why don’t we put soda lime in an open jar/ open air?

Soda-lime is highly unstable. It can absorb carbon dioxide and water vapours and can decompose immediately. Hence it is advisable to keep it in an airtight container. Its small crystals can cause breathing problems if they get into the windpipe.

8. Is soda-lime glass similar to soda-lime?

No, they both are different things. Soda-lime glass is one of the most commonly used glasses for bottles and window panes while soda lime has a variety of uses you just have read above. Soda-lime glass is much more stable than soda-lime chemically.