Sodium hydroxide

• Caustic soda
• Caustic soda
• Caustic ( s ) Soda
• Natriumoxydhydrat
• Sodium hydrate
• Sodium hydroxide solution ( aqueous solution)
• Soap stone
• E 524

White, odorless solid

Fixed

2.13 g · cm -3

322 ° C

1388 ° C

13 Pa (618 ° C)

Readily soluble in water: ( 1090 g · l-1 at 20 ° C)

Risk

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Sodium hydroxide ( caustic soda and caustic ( s ) Soda ), chemical formula NaOH, is a white hygroscopic solid. In water it dissolves to become very hot, by the negative enthalpy of solution of -44.5 kJ / mol for the strongly alkaline sodium hydroxide solution ( pH 14 at c = 1 mol / l). With the carbon dioxide of the air it reacts to form sodium bicarbonate and is therefore stored in hermetically sealed containers. To prevent the water binding sodium in the air, can be stored there together with a desiccant. The hydroxide ion displaces the strong base is weaker and volatile bases from their salts.

Production

Sodium hydroxide can be prepared in the laboratory by the reaction of sodium carbonate with calcium hydroxide to form sodium hydroxide and calcium carbonate:

The low solubility of calcium carbonate is filtered off. In the filtrate the highly soluble sodium hydroxide remains. This process caustification previously done on a large scale.

Another method is the highly exothermic reaction of elemental sodium with water to form sodium hydroxide and hydrogen:

In school, this attempt is often shown to demonstrate the reactivity of the alkali metals with water.

After evaporation, the solid sodium hydroxide is left:

The arable process for producing sodium hydroxide by electrolysis of sodium chloride was developed in the United States of America by Charles Ernest Acker ( March 19, 1868 -10. October 1920 ).

Further reactions

You Superimposed NaOH unlocked, it reacts with the carbon dioxide of the air to sodium bicarbonate or sodium carbonate, so it is stored in airtight containers.

In the laboratory, ammonia can be easily produced by the acid -base reaction of sodium hydroxide and ammonium chloride.

Electrolysis

Industrially, sodium hydroxide is produced by electrolysis of sodium chloride to caustic soda, hydrogen and chlorine gas:

There are for three different process technologies:

All methods have in common are additional purification and concentration stages, to reach anhydrous sodium hydroxide.

Commercial form

Sodium hydroxide comes in plastic containers packed in the form of small beads or pellets in the trade.

Use

Sodium hydroxide is mainly used in the form of sodium hydroxide solution and is one of the most important industrial chemicals. For its use see there. Solid sodium hydroxide is an essential component of drain cleaners.