Decahydrate, 4.33

Another mining process involves the recovery of sodium carbonate decahydrate from alkaline ponds. EMC mines this material from its solar evaporation pond using a bucket wheel dredge. The decahydrate slurry is dewatered, melted, and processed to soda ash. 

Tetrasodium hexakiscyanoferrate decahydrate [14434-22-1], Na4[Fe(CN)g] IOH2O, or yellow pmssiate of soda, forms yellow monoclinic crystals that are soluble in water but insoluble in alcohol. It is slightly efflorescent at room temperature, but the anhydrous material, tetrasodium hexakiscyanoferrate [13601 -19-9], Na4[Fe(CN)J, is obtained at 100°C. The decahydrate is produced from calcium cyanide, iron(II) sulfate, and sodium carbonate in a process similar to that for the production of K4[Fe(CN)g] 3H2O. It is used in the manufacture of trisodium hexakiscyanoferrate, black and blue dyes, as a metal surface coating, and in photographic processing. 

In the days of alchemy and the phlogiston theory, no system of nomenclature that would be considered logical ia the 1990s was possible. Names were not based on composition, but on historical association, eg, Glauber s salt for sodium sulfate decahydrate and Epsom salt for magnesium sulfate physical characteristics, eg, spirit of wiae for ethanol, oil of vitriol for sulfuric acid, butter of antimony for antimony trichloride, Hver of sulfur for potassium sulfide, and cream of tartar for potassium hydrogen tartrate or physiological behavior, eg, caustic soda for sodium hydroxide. Some of these common or trivial names persist, especially ia the nonchemical Hterature. Such names were a necessity at the time they were iatroduced because the concept of molecular stmcture had not been developed, and even elemental composition was incomplete or iadeterminate for many substances. 

TSPP is readily crystallised from water as the decahydrate between —0.4° and 79°C, and as the anhydrous salt above 79°C. The solubiUty of tetrasodium pyrophosphate is illustrated in Figure 8. The pH of a 1% solution is 10.2. TSPP is quite stable in alkaline medium but hydrolyses rapidly to orthophosphate under acid conditions. 

Water-soluble crystal modifiers such as yellow pmssiate of soda (YPS) (sodium ferrocyanide decahydrate) or ferric ammonium citrate may also be added to some types of salt as anticaking agents. Both are approved by the U.S. Food and Dmg Administration for use in food-grade salt. YPS and Pmssian Blue (ferric ferrocyanide), are most commonly added to rock salt used for wintertime highway deicing. Concentrations of YPS and Pmssian Blue in deicing salt vary, typically in the range of 20—100 ppm. 

Property Sodium sulfate Anhydrous Decahydrate Sodium hydrogen sulfate... 

Sodium sulfate decahydrate melts incongmently at 32.4°C to a sulfate Hquid phase and an anhydrous sulfate soHd phase. The presence of other salts, such as NaCl, can depress the melting poiat to 17.9°C. 

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

The solubihty—temperature curves for the Na20—B2O2—H2O system are given in Figure 5 (Table 9). The solubiUty curves of the penta- and decahydrates intersect at 60.6—60.8°C, indicating that the decahydrate, when added to a saturated solution above this temperature, dissolves with crystallisa tion of the pentahydrate and the reverse occurs below this temperature. This transition temperature may be lowered in solutions of inorganic salts, eg, 49.3°C in solutions saturated with sodium sulfate and 39.6°C with sodium chloride. Heats of solution for borax have been determined (67,73) and the manufacturer quotes a value of about 283 kJ/kg (67.6 kcal/mol) (33). 

Commonly known as the five hydrate (72), transition point to decahydrate, 60.7°C, 16.6% Na2B40y. Transition point to decahydrate, 58.2°C, 14.55% Na2B 02. 

To convert from kPa to mm Hg, multiply by 7.5. Values for the specific heat of aqueous borax (73) solutions as a function of weight percent decahydrate are... 

Heats of dehydration per mole of water vapor are (74) decahydrate to pentahydrate, 54.149 kj (12.942 kcal), and decahydrate to tetrahydrate, 54,074 kj (12.924 kcal). Borax stored over a saturated sucrose-sodium sucrose—sodium chloride solution maintains exacdy 10 moles of water and can thus be used as an analytical standard. Commercial borax tends to lose water of crystallisation if stored at high temperature or ia dry air. 

Rapid heating of either borax decahydrate or pentahydrate causes the crystal to dissolve before significant dehydration, and at about 140°C, puffing occurs from rapid vaporisation of water to form particles having as high as 90% void volume and very low bulk density (78). 

Solubihty data ia water are given ia Figure 5 and ia Table 9, solution pH ia Table 10, and the solubiUty ia organic solvents is given ia Table 7. Heats of solution ia water have been determined (68,73). The pentahydrate, ia contact with its aqueous solution, is metastable with respect to the tetrahydrate (kernite) at temperatures above 58.2°C and metastable to borax decahydrate below 60.6—60.8°C. Kernite can be slowly crystallised from a near saturate... 

Borax Decahydrate and Pentahydrate. Borax decahydrate and pentahydrate are produced from sodium borate ores, dry lake brines, colemanite, or magnesium borate ores. 

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. 

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. 

Sodium metaborate tetrahydrate can be prepared by cooling a solution containing borax and an amount of sodium hydroxide just in excess of the theoretical amount. The dihydrate is prepared by United States Borax Chemical Corp. by mixing appropriate quantities of borax penta- or decahydrate hydrate and aqueous NaOH to give a 46 to 52% solution concentration of Na20 20 (107). The mixture is then heated to about 90°C to dissolve all soHds and slowly cooled to 60—75°C. Crystals of the dihydrate ate then harvested and dried. 

Product Specifications. Specifications for the maximum allowable impurity levels for borate products are given in Table 12. Where maximum levels are not set, typical values are given. Typical levels of impurities generally fall well below the maximum specification. Both borax decahydrate and pentahydrate are sometimes overdried in manufacture and may give higher than theoretical assays. 

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). 

Refined or concentrated borax decahydrate and borax pentahydrate... 

Disodium Tetraborate Decahydrate, In the Urhted States, neady all the refined borax is used for household cleaning products. Small amounts are used as fertilizers and herbicides. USP-grade borax is used in cosmetic and toilet goods, in which purity is demanded. Special quahty-grade borax is used in electrolytic capacitors, in nuclear apphcations, and as a laboratory chemical. 

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