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Physical & Chemical properties

Melting point / freezing point

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Description of key information

The melting point of anhydrous ammonia is reported to be -77.7 °C (Merck Index).

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
196 K

Additional information

The melting point of anhydrous ammonia is reported to be -77.7 °C (Merck Index).

Aqueous ammonia, also known as ammonium hydroxide, only exists in solution. The freezing point is dependent on the concentration of the ammonia solution. At a concentration of 4%, the freezing point is -2.9C. As the concentration increases, the freezing point is lowered. At a concentration of 28%, the freezing point of the aqueous ammonia is -69.2C (Merck Index).

The freezing point of 29.4% aqueous ammonia is about -79.4 ⁰C (Postma, 1920).