Fused alkali or molten alkali refers to an alkali metal compound, typically hydroxide or carbonate, that is in its molten state due to high temperature. When an alkali metal compound, commonly sodium or potassium hydroxide or carbonate, is heated to its melting point, it transitions from a solid to a liquid state. In fused form, these compounds exhibit unique properties and reactivity compared to their solid counterparts.

Some key properties of fused alkalis:

High temperature stability: Fused alkalis have high melting points and remain liquid over a wide temperature range. For instance, sodium hydroxide melts at 318 °C (604 °F), and potassium hydroxide melts at 360 °C (680 °F).

High electrical conductivity: Molten alkali hydroxides are excellent conductors of electricity due to the presence of free hydroxyl ions (OH-) and alkali metal ions (e.g., Na+ or K+). This property is essential in various electrochemical processes.

Reactivity: Fused alkalis exhibit significant reactivity and are highly corrosive. They can dissolve or react with many metals, minerals, and organic materials. They are commonly used as cleaning agents and etching agents in industries.

Applications of fused alkalis:

Electrolytic production: Fused alkalis are used in the electrolytic production of metals such as sodium, potassium, and chlorine. The molten hydroxide is electrolyzed, and the liberated metals and chlorine gas are collected.

Glass production: Fused alkali carbonates are essential raw materials in the manufacture of glass. They act as fluxes that lower the melting point of silica and other glass components, resulting in the formation of a homogenous glass melt.

Petroleum refining: Fused alkalis are used as catalysts and additives in petroleum refining processes, where they aid in removing impurities and improving the quality of petroleum products.

Paper and pulp industry: Fused alkalis find application in the kraft process of paper production, where they are used to break down lignin in wood fibers, facilitating the separation of cellulose.

Textile industry: Fused alkalis are used in mercerization, a textile treatment process that involves treating cotton fibers with caustic soda to enhance strength, luster, and dye affinity.

Conclusion:

Fused alkali, molten alkali, or molten alkali hydroxides/carbonates are alkali metal compounds that are heated to their melting point, resulting in a liquid state. They possess high temperature stability, significant reactivity, and good electrical conductivity. Industrial applications of fused alkalis include electrolytic metal production, glass manufacturing, petroleum refining, and various industries involving processes like paper production, textile treatment, and cleaning. Safe handling precautions are essential due to their corrosive nature.