Borax pentahydrate

Most borax is produced from tincal (native borax) ore in a process that amounts to a large scale continuous recrystallization. Borax pentahydrate crystallizes in the Na20-B203-H20 system at appropriate concentrations above 67 °C. It contains two crystallographically unique 6-coordinate Na positions and three unique water positions. A more recent refinement of its structure shows that one of these water positions is not fully occupied, giving an actual composition of Na2[B40s(0H)4] 2.67 H2O [86]. 

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Table 7. Solubility of Boric Acid, Borax Decahydrate, and Borax Pentahydrate in Organic Solvents...

Pentahydrate is reversibly converted to an amorphous dihydrate, at 88°C and 0.26 kPa (2 mm Hg) or by boiling with xylene (73,75). The heat of dehydration for the pentahydrate to tetrahydrate has been calculated to be 53.697 kj (12.834 kcal) per mole of water (74). Thermogravimetric analyses show that 2.75 moles of water are lost on heating to 140°C. Like borax, pentahydrate puffs when heated rapidly to give a product having a bulk density of 0.042 g/mL (79). 

Commercial preparation of sodium perborate tetrahydrate is by reaction of a sodium metaborate solution, from sodium hydroxide and borax pentahydrate, and hydrogen peroxide followed by crystallization of tetrahydrate (95). The tnhydrate and monohydrate can be formed by reversible dehydration of the tetrahydrate. 

The derivatives plant is designed to aimuaHy produce 160,000 t of borax pentahydrate, 17,000 t of borax decahydrate, and 60,000 t of anhydrous borax. A reported 50,000 t of borax pentahydrate was produced in 1987. A sodium borate refinery is fed from stockpiled tincal ore or product from the concentration plant. The feed is dissolved using steam to give a solution 18% in The solution is then passed through a series of filters and sent to a... 

North American Chemical Co. produces borax pentahydrate and decahydrate from Seades Lake brines in both Trona and West End, California (see Chemicals frombrines). The 88 km dry lake consists of two brine layers, the analyses of which are given in Table 11. Two distinct procedures are used for the processing of upper and lower lake brines. Borax is produced in Trona from upper lake brines by an evaporative procedure involving the crystallization of potash and several other salts prior to borax crystallization as the pentahydrate (104). A carbonation process is used in West End, California to derive borate values from lower lake brines (105). Raw lower stmcture brine is carbonated to produce sodium bicarbonate, which is calcined and recrystallized as sodium carbonate monohydrate. The borate-rich filtrate is neutralized with lake brine and refrigerated to crystallize borax. 

Since 1970, the price per ton for bulk quantities of technical-grade borax pentahydrate from United States producers has changed dramatically. 

Refined or concentrated borax decahydrate and borax pentahydrate... 

Recovery Process. Boron values are recovered from brine of Seades Lake by North American Chemicals Corp. In one process the brine is heated to remove some water and burkeite. The remaining brine is cooled to remove potassium chloride. This cooled brine is then transferred to another crystallizer where borax pentahydrate, Na2B40y 5H20, precipitates (18). In a separate process, boron is removed by Hquid—Hquid extraction followed by stripping with dilute sulfuric acid (19). Evaporator-crystallizers are used to recover boric acid [10043-35-3] H BO. In a third process, borax is recovered by refrigerating a carbonated brine. 

Borax pentahydrate occurs in nature as mineral tincalconite, formed by dehydration of borax. It has several industrial applications, mostly the same as its decahydrate. The pentahydrate is used in the manufacture of borosili-cate glass. It also is used in cleaning agents ceramic glaze adhesives cosmetics antifreeze and herbicide formulations. It is added to fertihzers to provide boron as a nutrient to the plants. 

Borax pentahydrate is produced from various sodium borate and magnesium borate ores. In the United States, it is produced from dry lake brines, colemanite and tincal. It is commercially produced along with the decahy-drate. The production processes are similar to decahydrate (see Borax dec-ahydrate). 

Fig. 19. Borax structure, where x = 8 for borax decahydrate and x = 2.67 for borax pentahydrate...

Keywords Borax pentahydrate Anhydrous borax Calcium oxide Coating... 

Production of BA without fusion is very attractive with respect to energy consumption and corrosion. Thus, the attempts have mostly been in dehydration borax pentahydrate in a fluidized bed via a stage-wise calcination [4,5]. The main disadvantage of this process is the puffing of the par-... 

Fig. 5. Microscopic photographs of borax pentahydrate (a) pure, (b) containing 0.67wt.% Ca2+ and (c) containing 2.5 wt.% Ca2+.

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