Sodium Hydroxide: Applications, Preparation Processes, Industrial Chain and Safety Guidelines

Sodium Hydroxide also known as Caustic Soda and Lye, its chemical formula is NaOH with CAS No. 1310-73-2 and molecular weight of approximately 40.00. It is a strong alkaline substance with severe corrosivity.

Physical and Chemical Properties

Pure sodium hydroxide appears as colorless transparent crystals. Industrial-grade products are opaque white crystals due to trace sodium chloride and sodium carbonate impurities, commonly available in lump, flake, granular and rod forms. Key physical parameters are listed below:表格

Physical Parameter	Value
Density	2.130 g/cm³
Melting Point	318.4℃
Boiling Point	1390℃
Water Solubility (0℃)	42%
Water Solubility (20℃)	109%
Water Solubility (100℃)	347%

Solubility: Easily soluble in water, ethanol and glycerol; insoluble in ether and acetone.

Property Description

• Solubility: Highly soluble in water with massive heat release during dissolution. Its aqueous solution is strongly alkaline, featuring astringent taste and slippery texture. Solid sodium hydroxide dissolves readily in glycerol and ethanol, yet insoluble in acetone and ether.
• Deliquescence: Solid sodium hydroxide is highly deliquescent in air, absorbing atmospheric moisture and eventually dissolving into liquid.
• Hygroscopicity: Solid caustic soda has strong hygroscopicity, while liquid sodium hydroxide has no such property.

It possesses typical strong alkalinity and undergoes neutralization reaction with acids to generate salt and water. Prone to deterioration by absorbing carbon dioxide in air and forming sodium carbonate, hence sealed and moisture-proof storage is required. It undergoes disproportionation reaction with halogens including chlorine, bromine and iodine, and corrodes certain metals and materials under high temperature.

Industrial Chain

Upstream

Raw materials: Crude salt and electric power. Production of one ton of caustic soda consumes 2300-2400 kWh electricity and 1.4-1.6 tons crude salt. Electricity accounts for 50%-60% of production cost, and crude salt takes up 20%-25%.

Midstream

Chlor-alkali production. Saturated brine is electrolyzed to produce caustic soda, chlorine and hydrogen simultaneously. Restricted liquid chlorine transportation pushes manufacturers to match PVC production to consume chlorine, realizing balanced production of alkali and chlorine.

Downstream Application & Consumption Ratio (2024 Reference)

• Alumina industry: 28%-32%
• Chemical industry: 13%-16%
• Printing, dyeing and chemical fiber industry: about 13%
• Papermaking industry: about 12%
• Water treatment industry: about 9%
• New energy (lithium battery materials): emerging growing sector
• Others (petroleum, soap, food processing etc.): about 9%

Preparation Methods

表格

Method	Raw Material	Core Reaction Condition	Features	Current Status
Causticization Process	Soda ash & milk of lime	Around 99-101℃	Simple process, high energy consumption	Small-scale production
Diaphragm Electrolysis	Saturated crude salt water	Electrolysis	Low product purity, environmental pollution risk	Basically phased out
Ion-exchange Membrane Electrolysis	Refined salt water	Electrolysis with cation selective membrane	High purity (≥99.5%), low energy consumption, pollution-free	Dominant mainstream, occupying about 95% market share

Application Fields

表格

Downstream Industry	Main Application	Reference Consumption Ratio
Alumina	Bauxite digestion via Bayer process	28%-32%
Chemical Industry	Synthesis of organic and inorganic chemicals	13%-16%
Printing, Dyeing & Chemical Fiber	Desizing, scouring, mercerizing and viscose fiber production	about 13%
Papermaking	Alkaline pulping and cellulose separation	about 12%
Water Treatment	pH adjustment, heavy metal precipitation and resin regeneration	about 9%
New Energy	Cathode material production for lithium batteries	Emerging growth
Others	Petroleum refining, soap making, food processing, glass and enamel manufacturing	about 9%

Safe Operation and Transportation Storage

Class 8 corrosive dangerous goods. Strong alkalinity causes corrosion to skin, mucous membrane, fabrics and metals.

Dissolution Operation: Add caustic soda into water with continuous stirring. Never pour water into caustic soda to avoid boiling splashing caused by intense heat release.

Emergency Treatment: Flush contacted skin and eyes with abundant running water for no less than 15 minutes. Do not neutralize with acid to prevent secondary thermal injury. Seek medical treatment timely when necessary.

Storage Requirement: Keep sealed and dry, store away from acids and active metal powder to avoid moisture-induced deterioration.