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Vapour pressure

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Description of key information

Not applicable, ionic liquids are not volatile.

Key value for chemical safety assessment

Additional information

Ionic liquids are salts which melt below 100°C, preferential below room temperature.

This for salts unusual behaviour belongs to the fact that the constructive ions have a delocalised charge distribution and are asymmetrical.

That’s why they grab inefficiently into undefined structures in the ion-lattice.

This ineffective and less precise package leads to less energy of crystallisation, higher entropy and therefore low melting points.

The inefficient packing of the ions can not prevent that the interaction among them is strong enough to prevent boiling at atmosphere pressure. Hence ionic liquids are not volatile.