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

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    $\begingroup$ 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

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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).

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

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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.

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  • $\begingroup$ 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
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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.

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