Acids and bases
Calcium oxide vs calcium hydroxide
Calcium oxide (CaO, CAS 1305-78-8) and calcium hydroxide (H2CaO2, CAS 1305-62-0) are both listed under acidulants and acidity regulators.
Calcium oxide has a molar mass of 56.08 g/mol, calcium hydroxide 74.09 g/mol.
Measured melting points are 2,613 °C for calcium oxide and 580 °C for calcium hydroxide.
Both carry the GHS signal word Danger.
On CompoundList, 278 suppliers list calcium oxide and 496 suppliers list calcium hydroxide.
Data last updated 7 October 2026
 |  | |
|---|---|---|
| Identity | ||
| Name in our database | Calcium oxide | Calcium hydroxide |
| CAS number | 1305-78-8 | 1305-62-0 |
| Molecular formula | CaO | H2CaO2 |
| Molar mass | 56.08 g/mol | 74.09 g/mol |
| IUPAC name | oxocalcium | calcium dihydroxide |
| EC number | 215-138-9 | 215-137-3 |
| Physical properties | ||
| Appearance | Grey-white, cubic crystals | Crystals or soft granules or powder |
| Melting point | 2,613 °C | 580 °C |
| Boiling point | 2,850 °C | Decomposes |
| Density | 3.34 g/cm³ | Approximately 2.2 g/cm³ |
| Flash point | Not flammable | /Calcium Hydroxide is/ non flammable |
| Solubility | Soluble in water forming calcium hydroxide and generating large a quantity of heat. | Solubility in water is decreased by the presence of fixed alkali hydroxides. |
| LogP (octanol/water)Computed from the structure | -0.5 | -0.73 |
| Safety (GHS) | ||
| Signal word | Danger | Danger |
| Pictograms | ||
| Hazard statements |
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| UN number | UN 1910 | Not recorded |
| Uses and classification | ||
| Uses and functions |
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| Category | Inorganic chemicals › Oxides and peroxides | Inorganic chemicals › Hydroxides and bases |
| HS code | 282590Hydrazine and hydroxylamine and their inorganic salts, other inorganic bases, other… | 282590Hydrazine and hydroxylamine and their inorganic salts, other inorganic bases, other… |
| Market on CompoundList | ||
| Suppliers | 278 suppliers | 496 suppliers |
| Supplier countries | 34 countries, most in United States, India, China | 55 countries, most in India, United States, China |
| Price rangeOnly prices set by suppliers who manage their own profile | Price on request | Price on request |
Measured and computed values as shown on each chemical page, plus live listings on CompoundList. Details may have changed, please confirm them with the supplier. Safety data is a summary, not an SDS.
Calcium hydroxide
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