Borax pentahydrate or disodium tetraborate pentahydrate has chemical formula Na2B4O7.5H2O. The physical preperties of borax pentahydrate is soft colorless hexagonal crystal and it is soluble in water and alcohols (17% in methanol and 31% in ethylene glycol by weight). In nature, borax pentahydrate occurs as mineral tincalconite, formed by dehydration of borax. Borax pentahydrate will decompose on heating and reversibly converted to an amorphous dihydrate when heated at 88 degree celcius at 2 torr.
The production processes of borax pentahydrate are similar to borax decahydrate. Borax obtained from lake brines, tincal, and colemanite is separated from the constituent salts. The hot liquor obtained is consisted of borate and potassium salt (KCl). To remove the potassium salt, the insoluble solid particles are filtered out and the hot liquor is cooled in continuous vacuum crystallizers under controlled conditions of temperatures and concentration to crystallize KCl. KCl is separated from the liquor by filtration and bicarbonate is added to the liquor to prevent the formation of sodium metaborate. The liquor is evaporated and refrigerated to crytallize borax decahydrate. Borax pentahydrate will be produced by dehydrating borax pentahydrate.
Borax pentahydrate applications are mostly the same as borax decahydrate. It can be used as cleaning agent, adhesives, cosmetics, and antifreeze. Borax pentahydrate can also be added to fertilizers to provide boron as a nutrient to the plants.
Borax Pentahydrate is used to control the network formed by glass melt and increase the strength of final product.
Borax pentahydrate is used to increase scratch resistance as well as chemical resistance of ceramics & enameled appliances. The usage of borax in ceramic & enamels industry results in a smooth & strong finished product.
Borax pentahydrate is commonly used to manufacture sodium perborate, which is one of the main bleaching agent in laundry powders.
Borax decahydrate is also used for waxes and it can also be used as a car antifreeze formulation.