Borax (or sodium tetraborate decahydrate) is a white coloured inorganic powder having the formula Na2B4O7·10H2O or Na2[B4O5(OH)4]·8H2O. It is a compound of the element Boron and is also a salt of the compound called boric acid. It occurs naturally as Evaporite, or as a combination of various hydrates of borax. Some of the major properties of borax are its high solubility in water, its ability to produce a yellowish green coloured flame when ignited, it acts a mild alkaline salt, its good chemical stability, and it has good buffering and fluxing properties.
The most commercial methods for producing borax starts from the usage of the natural minerals available in mines or lakes. The slurry consisting of a mixture of minerals like ulexite, colemanite, etc, are pumped to solar evaporation ponds. Impurities such as sodium chloride, sodium bicarbonate, and sodium sulfate are concentrated and crystallized and are removed either by filteration or by rapid cooling to ensure selective crystallisation. The filtered brine is then reacted with sulphate cake derived from the liquid-liquid extraction process product to get potassium sulphate and potassium chloride, which are further precipitated. The resulting solution is cooled such that borax pentahydrate is precipitated from the remaining solution. This borax compound is then redissolved, hydrated, and then filtered to finally produce borax decahydrate.
Soap and Detergent Industry
It is most widely used as a pH buffering agent and a mild abrasive in products as diverse as cosmetic soaps, detergents, glass/metal cleaners, etc. It is also used in cosmetic items like lotions and creams as a crosslinking agent.
It is used to dissolve certain metal oxides in order to recover metals such as brass, copper, lead, and zinc.
Due to its ability to prevent ferrous metals from oxidising, they are used in coolants and antifreeze for automobiles.
It is used in starch formulations for making adhesives for corrugated paperboards and paper. It is also used for making dextrin based adhesives.
It also finds application as stabilizers and bonding agents for refractories, flame retardant, catalyst for organic dyes, and coolant for diesel engines.