Borax Anhydrous

Crystalline anhydrous borax takes up some water from moist air even at 300°C. It becomes anhydrous near 700°C and melts at 742.5°C. The heat of hydration to borax has been calculated as 161 kJ/mol (38.5 kcal /mol) of Na20 2B202 (73,82). The heat of fusion has been reported as 81.2 kJ/mol (19.4 kcal/mol) (17). 

A single-crystal x-ray diffraction study has shown that the borate anion in anhydrous borax is polymeric in nature and is formed via oxygen bridging of triborate and pentaborate groups (83). The chemistry of anhydrous borax has been reviewed (73,84). 

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... 

Anhydrous Borax. Anhydrous borax is produced from its hydrated forms, borax decahydrate or pentahydrate, by fusion (Pig. 6). Low temperature calcining is usually an intermediate step to remove water of hydration. This material is fed to a refractory brick-lined furnace and fused to a mobile Hquid at about 1000°C. 

Fig. 6. Flow sheet for the production of anhydrous borax (standard and fines) at Seades Lake, Trona, California (105).

To produce amorphous anhydrous borax, the molten borax is mn between two large water-cooled roUs, forming sheets about 1.6 mm thick, which ate then cmshed and screened to the desired particle size. Because the borax is cooled rapidly by the roUs, it remains largely amorphous, though it may contain some crystalline anhydrous borax. 

In general, the production of fused materials is much more energy intensive than that of hydrated products, and this difference is reflected in their prices. The primary producers are the United States Borax Chemical Corp. and the North American Chemical Co. Yearly fusion capacities for the two companies ate reported to be 86,000 and 36,000 metric tons B2O2, respectively (6). There is a plant in Turkey designed for the production of 60,000 t/yr of refined anhydrous borax from tincal ore (102). Small quantities of anhydrous borax have been produced in Argentina. 

Decahydrate, Pentahydrate, and Anhydrous Borax and Bulk Calcium Borates. The bulk borate products, borax decahydrate and pentahydrate, anhydrous borax, boric acid and oxide, and upgraded colemanite and ulexite, account in both toimage and monetary terms for over 99% of sales of the boron primary products industry (6). Economic considerations for all these products are highly interrelated, and most production and trade statistics do not distinguish the various products. 

In 1986, Turkey produced nearly one million metric tons of mineral concentrate, whereas production of refined borate chemicals was 89,500 metric tons. Annual production capacities of chemicals at Eskiseher were pentahydrate borax, 160,000 t anhydrous borax, 60,000 t and decahydrate borax, 17,000 t. Capacities at Bandermes were decahydrate borax, 55,000 t boric acid, 33,000 t and sodium perborate, 64,000 t (103). 

Disodium Tetraborate, In the Urhted States, anhydrous borax finds most apphcation in the glass industry for enamels, borosihcate glass, and fiber glass insulation. It is also used as an antifreeze additive and as an algicide in industrial water. 

Synonyms sodium tetraborate disodium tetraborate anhydrous borax... 

Anhydrous borax is used in the manufacture of glasses, glass wool, and metallurgical fluxes. Other uses are in enamels, frits, and glazes. It also is applied in fertilizers. 

Dehydration gives pentahydrate, Na2B407 5H20 and other lower hydrates. Calcination at elevated temperatures gives anhydrous borax. 

Similar reactions occur with many other chlorine-containing compounds, BCI3 being produced (see Boron Trichloride reactions). Anhydrous borax and BCI3 are obtained when it is heated with sodium chloride at 800°C ... 

H. le Chatelier gives 940°. The latter also measured the m.p. of mixtures of this compound with anhydrous borax (melting at 970°), and found a maximum in the curve at 960° and 58 3 per cent, of tetrasodium pyrophosphate corresponding with the compound Na4P207.3Na2B407, with eutectics at 910° and 850° corresponding respectively with 16 7 and 83 7 per cent, of the pyrophosphate. According to... 

NF-grade borax decahydrate is manufactured to conform to standards of the National Formulary, XV ed., for sodium borate. Maximum allowable impurity levels for technical anhydrous borax are SO2- 0.41% Si02, 0.21% A1203, 0.14% CaO, 0.03% MgO, 0.15% and Fe203, 0.02%. 

Hard, colorless crystals, or crystalline pieces, soluble in 17 parts of cold, and in 0.5 part of boiling, water, freely soluble in glycerin, but insoluble in alcohol. When borax is heated, it swells up, the water of crystallization being expelled, and at a red heat the anhydrous borax fuses to a transparent, colorless mass. 

Keywords Borax pentahydrate Anhydrous borax Calcium oxide Coating... 

The obtained anhydrous borax is very fragile, thus it can be easily converted to powder form by grinding. This operation increases the bulk density of BA. 

In order to obtain anhydrous borax with low bulk density by calcination in batch calcinator, particular attention is paid to cover BPH surface with Ca(OH)2 layer. The following conclusion can be withdrawn from the results obtained during the calcination of covered BPH particles in a batch calcinator ... 

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