Difference Between Quicklime and Hydrated Lime l Quicklime vs Hydrated Lime

The key difference between quicklime and hydrated lime is that the quicklime (or burnt lime) contains calcium oxide whereas the hydrated lime (slaked lime) contains calcium hydroxide.

The major source for both quicklime and hydrated lime is the limestone. Therefore, like limestone, these compounds are also alkaline. We call quicklime as “burnt lime” because we produce it by the thermal decomposition of limestone. We call hydrated lime as “slaked lime” because we produce it by quenching quicklime with water.


1. Overview and Key Difference
2. What is Quicklime
3. What is Hydrated Lime
4. Side by Side Comparison – Quicklime vs Hydrated Lime in Tabular Form
5. Summary

What is Quicklime?

Quicklime is calcium oxide. We produce it by the thermal decomposition of limestone. Therefore, we call it “burnt lime”. Limestone contains calcium carbonate. We burn this material to above 825 °C. we call this process “calcination”. It liberates carbon dioxide forming quicklime. This substance is relatively inexpensive.

The chemical formula of the compound is CaO. Its molar mass is 56.07 g/mol. It appears as a white to pale yellow powder. Moreover, it is odorless. The melting point and boiling points are 2,613 °C and2,850 °C respectively. This compound is highly water soluble; it forms calcium hydroxide. The crystal structure of this compound is cubic.


There are many uses of this compound which includes its applications in basic oxygen steelmaking process, in the production of aerated concrete blocks, as a component in producing glass, organic chemicals, etc. Moreover, it is a key ingredient in producing cement.

What is Hydrated Lime?

Hydrated lime is calcium hydroxide. We call it “slaked lime” as well. This is because we produce calcium hydroxide via quenching calcium oxide with water. In addition to that, there are many other synonyms for this compound, i.e. caustic lime, builder’s lime, slack lime, pickling lime, etc. A saturated solution of calcium hydroxide is called “lime water”.

The chemical formula of this compound is Ca(OH)2. The molar mass of this compound is 74.09 g/mol. It appears as a white powder and is odorless. The melting point is 580 °C, and it decomposes upon further heating (it releases water vapor). However, the solubility of this compound in water is poor.

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