What is the liquid sodium hydroxide freezing point?
Liquid sodium hydroxide reaches freezing point and not because of the recent cold front sweeping the east coast. As discussed on the Puritan blog, the liquid sodium hydroxide freezing point varies depending on the concentration, and the relationship is not linear. Sodium hydroxide forms an approximately 50% by weight saturated solution with water.
The freezing points of some of the more common concentrations are:
5% NaOH -4°C / 25°F
10% NaOH -10°C / 14°F
30% NaOH 1°C / 34°F
50% NaOH 12°C / 53.6°F
What happens when sodium hydroxide solutions freeze? A 50% by weight solution of sodium hydroxide begins to congeal and crystalize at temperatures as high as 10 – 12°C (50 – 53.6°F), so it should be stored above 15.5°C (60°F). If the solution does freeze due to cold weather, it should be completely thawed and then mixed thoroughly before use. The thawed material may appear turbid due to a small amount of salt precipitate that remains in suspension. Sodium hydroxide solutions also have a tendency to pick up carbon dioxide from the air, forming sodium carbonate if exposed for long periods of time at temperatures above 25°C (77°F). Try to limit air exposure in order to minimize formation of sodium carbonate, which can also cause cloudiness.