What is Soda Lime?

Soda lime is a white to grayish-white coloured 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 is how a soda lime looks like:

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This page discusses the soda lime, soda lime formula, soda lime formula equation, soda lime molecular formula, soda lime composition, 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 CO2 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 glass. 


Soda lime reacts with CO2 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 CO2 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 molecular formula is CaHNaO2.


Soda Lime Composition

The chemical components included in the Soda Lime formation are:

  • Calcium oxide, CaO (about 75%)

  • Water, H2O (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:

  1. Thermal Conductivity: 0.937 W/mK

  2. Density (at 20 °C/68 °F): 2.44 g/cm3

  3. Hardness (Mohs Scale): 6 - 7

  4. Knoop Hardness: 585 kg/mm2 + 20

  5. Modulus of Elasticity (Young's): 7.2 x 1010 Pa

  6. Modulus of Rigidity (Shear): 3.0 x 1010 Pa

  7. Bulk Modulus: 4.3 x 1010 Pa

  8. Poisson's Ratio: 0.22

  9. Specific Gravity: 2.53

  10. Specific Heat: 0.21

  11. Specific Weight: 2,483 g/cm3

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

  13. Softening Point: 726°C/1340°F

  14. Annealing Range: 546°C/1015°F

  15. 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 (H2O) 

~ 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 CO2 in both the substance research centre and mechanical applications, for example, shut breathing conditions for example submarines, SCUBA re-breathing contraption, decompression chambers, and hyperbaric chambers, and so forth.


Soda Lime Formula Equation

The fundamental overall reaction of CO2 absorption with soda lime is as per the following;- 

Ca(OH)2 + CO2     →     CaCO3 + H2

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:

CO2 + NaOH    →      NaHCO3 …..(1)

Now,  NaHCO3 reacts further with slaked lime to form caustic soda:

Further Reaction:  NaHCO3      +    Ca(OH)2    →   CaCO3      +      H2O    +    NaOH …..(2)

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

The development of water in the last response additionally accelerates the assimilation of CO2 by going about as a dissolvable to disintegrate CO2 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 CO2 during anaesthesia/insensibility. It can be unified in a Mapleson C system or a circle system.

The Reaction:

  1. H2O + CO2 ====> H2CO3

                              high pH

  1. H2CO3 + 2 NaOH ====> Na2CO3 + 2H2O

                                        high pH

  1. Na2CO3 + Ca(OH)2 ====> CaCO3 + 2 NaOH

                                          high pH             

  1. H2CO3 + Ca(OH)2 ====> CaCO3 + 2H2O

                                        high pH

Point to Note:

Reaction 4 happens just at a lethargic rate in these absorbents. 

CO2 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 Uses

  • Carbon dioxide retentive - soft drink/soda lime.

  • Soda lime, a carbon dioxide permeable utilized in closed circuit breathing device/climate.

  • High Activity - mines rescue, submerged diving.

  • Medium Activity - Chimney cleaning, working in a dangerous climate.

  • Low Activity - anesthesia room, refuse chamber.

  • Arsenic adsorbent.

FAQs (Frequently Asked Questions)

Q1: Differentiate Between Lime and Soda Lime.

Ans: 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.

Q2: What is the difference between the Cold Lime Soda Process and the Hot Lime Soda Processes?

Ans: 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.

Q3: What is Ca(OH)2?

Ans: 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.