The chemicals "quick lime", "slaked lime", "lime water" and "soda lime" all have "lime" in common. What is the difference between them?

  • 2
    $\begingroup$ Aha, I wondered if this would be a self-answer -- most or all of this is on Wikipedia. $\endgroup$
    – hBy2Py
    Jan 21, 2017 at 16:00
  • $\begingroup$ 'Milk of lime' is somewhat similar to limewater. It is the suspension of slaked lime in water whereas limewater is a true solution. $\endgroup$ May 26, 2022 at 3:38

4 Answers 4


Quick lime is calcium oxide, $\ce{CaO}$, in the solid state.

Slaked lime is calcium hydroxide, $\ce{Ca(OH)2}$, in the solid state.

Lime water is a dilute solution of calcium hydroxide, $\ce{Ca(OH)2}$, in water.

Soda lime is a mixture of sodium hydroxide, $\ce{NaOH}$, (also known as caustic soda) and calcium oxide, $\ce{CaO}$, (also known as quicklime).

  • 1
    $\begingroup$ Thanks for posting this! Can you add links to Wikipedia or elsewhere? Most of these are on Wik. $\endgroup$
    – hBy2Py
    Jan 21, 2017 at 16:01
  • $\begingroup$ @hBy2Py, I did not refer to wikipedia. I knew this. $\endgroup$
    – MrAP
    Jan 21, 2017 at 16:02
  • 6
    $\begingroup$ You may know these things, but including links to outside sources increases the usefulness of your answer to others. $\endgroup$
    – Ben Norris
    Jan 21, 2017 at 17:36
  • $\begingroup$ Slaked lime comes from the idea of slaking the "thirst" of quick ("live" or "active") lime with water. Sort of an alchemical etymology. $\endgroup$ Aug 4, 2019 at 14:39

To add to the family of materials in the 'lime' category: The sedimentary rock limestone is composed of calcium carbonate, $\ce{CaCO3}$.


According to Wikipedia:

Quick lime is $\ce{CaO}$ (calcium oxide)
Slaked lime is $\ce{Ca(OH)2}$ (calcium hydroxide)
Lime water is just a dilute solution of calcium hydroxide.
Soda lime is a mixture of about 75% calcium hydroxide, a few percent each of sodium hydroxide and potassium hydroxide, and about 20% water. It is commonly used to adsorb $\ce{CO2}$ from the air.

  • $\begingroup$ Soda lime works great for adsorbing other acidic gases, too: $\ce{NO2}$, $\ce{SO3}$, etc. I used it in my grad work for $\ce{NO2}$. $\endgroup$
    – hBy2Py
    May 16, 2022 at 15:27

I completely understand your frustration as all those names are trivial names (non-systematic.)

The "lime" is derived from the use of Limestone https://www.etymonline.com/word/lime

I would have to mention that even those names are associated with chemical names that are not pure and contain some impurities.

Lime = quicklime ($\ce{CaO}$ - Calcium oxide) is made from limestone ($\ce{CaCO3}$ - Calcium carbonate) by decarbonisation at high temperatures.

To get slaked lime = hydrated lime ($\ce{Ca(OH)2}$ - Calcium hydroxide) you mix Lime with water, resulting in a white powdery substance.

In another process, you can make lime water - where you add lime into a greater amount of water resulting in water solution/suspension of hydrated lime $\ce{Ca(OH)2}$ in water - this is also called milk of lime.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.