Dehydration hexahydrate

Both forms sublime very readily, even at room temperature a small sample on exposure to the air will completely volatilise in a short time, particularly on a warm day or if the sample is exposed to a gentle current of air. Hence the above method for rapid drying. A sample confined in an atmospheric desiccator over calcium chloride rapidly disappears as the vapour is adsorbed by the calcium chloride. A sample of the hexahydrate similarly confined over sodium hydroxide undergoes steady dehydration with initial liquefaction, for the m.p. of the hydrated-anhydrous mixture is below room temperature as the dehydration proceeds to completion, complete resolidification occurs. 

Sodium Peroxoborate. Sodium peroxoborate [10332-33-9] (sodium perborate monohydrate), Na2[82(02)2(011)4], formerly written as NaBO H20, is known only as a microcrystalline powder, made by dehydrating the hexahydrate. The crystal stmcture has not been deterrnined, but the vibrational spectmm (27) indicates the presence of the same cycHc peroxodiborate anion (4) as that in the hexahydrate as well as in the tetrahydrate. 

In 1993, the world capacity for sodium peroxoborate hexahydrate (tetrahydrate) was about 900,000 metric tons, of which about one-third was converted to the dehydrated compound (monohydrate). At the then prevailing prices, the total value of this business was about 6 x 10 . The world capacity for sodium carbonate peroxohydrate (percarbonate) was about 60,000 metric tons, valued at about 70 x 10 . ... 

The most common form of calcium thiosulfate is the hexahydrate [10035-02-6] CaS202 6H20, which has triclinic crystals and a density of 1.872 g/cm at 16°C (84). Heating, however, does not give the anhydrous salt because of decomposition at 80°C. At lower temperatures, dehydration stops at the monohydrate [15091-91-5]. The solubiUty of calcium thiosulfates in water is as follows ... 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

Cobalt(II) chloride hexahydrate [7791-13-1], C0CI2 6H20 is a deep red monoclinic crystalline material that deflquesces. It is prepared by reaction of hydrochloric acid with the metal, simple oxide, mixed valence oxides, carbonate, or hydroxide. A high purity cobalt chloride has also been prepared electrolyticaHy (4). The chloride is very soluble in water and alcohols. The dehydration of the hexahydrate occurs stepwise ... 

Cupric nitrate (3H2O) [10031-43-3 (3H2O) 3251-23-8 (anhydr)] M 241.6, m 114 , b 170 (dec), d 2.0. Crystd from weak aqueous HNO3 (0.5mL/g) by cooling from room temperature. The anhydrous salt can be prepared by dissolving copper metal in a 1 1 mixture of liquid NO2 and ethyl acetate and purified by sublimation [Evans et al. J Chem Soc, Faraday Trans 1 75 1023 1979], The hexahydrate dehydr to trihydrate at 26°, and the anhydrous salt sublimes between 150 and 225°, but melts at 255-256° and is deliquescent. 

Mn(C104)i, mw 253.84, OB to MnO HC1 +25.2% the hexahydrate is obtained as pale rose needles (Ref 2) Qf ealed to be —90kcal/ mole (Ref 5) CA Registry No 13770-16-6 Preparation. The hexahydrate, Mn(H20) -(ClO02, has been prepd by dissolving Mn-hydroxide or carbonate in dil perchloric ac followed by evapn of the soln until crysts appear (Ref 2). Attempts to dehydrate it by heating with an excess of 2,2-dimethoxypropane resulted in severe explns when the temp was raised above 65° (Ref 6)... 

In view of the ready commercial availability and apparent stability of the hexahy-drate, it is probable that the earlier report of explosion on impact, and deflagration on rapid heating [1] referred to the material produced by partial dehydration at 100°C, rather than the hexahydrate [2], The caked crystalline hydrated salt, prepared from aqueous perchloric acid and excess cobalt carbonate with subsequent heated evaporation, exploded violently when placed in a mortar and tapped gently to break up the crystalline mass, when a nearby dish of the salt also exploded [3]. Subsequent investigation revealed the probable cause as heating the solid stable hexahydrate to a temperature ( 150°C) at which partial loss of water produced a lower and endothermic hydrate (possibly a trihydrate) capable of explosive decomposition. This hazard may also exist for other hydrated metal perchlorates, and general caution is urged [4,5],... 

Fe HB(C2H2N3)3 2] has been obtained by dehydration under heating of the low-spin hexahydrate. The crystal structure for this hexahydrate has been determined at room temperature [17]. It clearly contains Fe(II) ions in the low-spin state (average Fe-N distance=1.99 A). The dehydrated derivative [Fe HB(C2H2N3)3 2] has been reported to exhibit a very abrupt spin transition between 334-345 K via variable temperature UV-vis and 57Fe Mossbauer spectroscopy studies [19]. After the publication of a preliminary magnetic study in 1994 [19], a more detailed report appeared in 1998 [20]. 

Magnesium chloride hexahydrate, 15 394 dehydration of, 15 328 Magnesium chromate, molecular formula, properties, and uses, 6 562t Magnesium chromite, molecular formula, properties, and uses, 6 563t Magnesium citrate, molecular formula, 6 638t... 

Nickel silicate, as catalyst, 20 106-109 differential thermogram of xerogel, 20 107 infrared spectra of, 20 108 preparation by SHCP method, 20 106 properties and structure of, 20 107-109 X-ray diffraction pattern of, 20 109 Nickel sulfate hexahydrate, dehydration of, dislocations and, 19 389 Nickel sulfides... 

Various preparative methods are adopted at nonstoichiometric formulations, incomplete dehydration or using oxide additives to obtain boron phosphate of varying purity for its catalytic applications. The compound also forms hydrates (tri- tetra-, penta-, and hexahydrates) which readily decompose in water to phosphoric acid and boric acid. 

Calcium chloride has several industrial applications. The major applications of this compound are in deicing of roads, dust control, imparting stability to roads and buildings, and to improve traction in tractor tires. It is mixed with ice to make freezing mixtures. Hexahydrate mixed with crushed ice can lower the temperature of the cooling bath to below -50°C. It also is used as a desiccant for dehydrating gases and liquids. It is added to cement in various proportions to manufacture different types of concrete. Other uses are in adhesives, to lower gel temperatures, and as a calcium source in liquid feed supplements for dairy cattle. Also, the compound is used to control particle size development and reduce coalescence in plastics. 

The solution on concentration and cooling forms crystals of hexahydrate which on heating with SOCI2 dehydrates to anhydrous cobalt(II) chloride. Alternatively, the hexahydrate may be converted to anhydrous C0CI2 by dehydration in a stream of hydrogen chloride and dried in vacuum at 100-150°C. The anhydrous compound also may be obtained by passing chlorine over cobalt powder. 

The anhydrous salt of cobalt(II) suhate is a red orthogonal crystal density 3.71g/cm3 melts above 700°C the monohydrate is red orthogonal crystal having a density of 3.08 g/cm the heptahydrate is a pink salt, monoclinic prismatic crystals, density 2.03 g/cm heptahydrate dehydrates to hexahydrate at 41°C and converts to monohydrate at 74°C the anhydrous salt and heptahy-drates are soluble in water monohydrate slowly dissolves in boiling water. 

The insoluble Mg(OH)2 is filtered off and the seawater containing calcium chloride is returned to the sea. The hydroxide is then neutralized with hydrochloric acid. Evaporation of the solution yields hexahydrate, MgCb 6H2O. The hexahydrate is either fuUy dehydrated to anhydrous MgCE by heating in dryers or partially dehydrated to monohydrate for electrolytic... 

The product obtained is always the hexahydrate, MgCl2 6H20. It is dehydrated to anhydrous magnesium chloride by spray drying and heating with dry hydrogen chloride gas. In the absence of HCl, heating hexahydrate yields the basic salt, Mg(OH)Cl ... 

Nickel nitrate hexahydrate may be prepared by several methods based on the reaction of dilute nitric acid on nickel powder, nickel oxide or nickel carbonate. The reaction is exothermic and requires controlled cooling during production. The hexahydrate can be dehydrated to anhydrous salt by treatment with fuming nitric acid. 

Both forms of anhydrous sodium triphosphate are unstable with respect to combination with water, and cannot therefore be prepared from aqueous solution. Likewise they cannot be obtained by dehydration of the hexahydrate (19, 141, 142, 326) as long as the dehydration temperature is less than 150°C. When the hexahydrate is heated in an open atmosphere to about 120° it first loses only about five molecules of water (238, 317). The residual molecule of water simultaneously causes hydrolysis and splits the triphosphate anion to crystalline diphosphate and amorphous monophosphate, perhaps according to the equation ... 

The low temperature form of the triphosphate, Na6P30io(II), is formed with the loss of residual water from the mixture of decomposition products by raising the temperature to 130-150°C. Direct dehydration to NaBP30io(II) also occurs, partially at least, by simply and directly heating the hexahydrate in vacuum or in boiling toluene (110.8°C) (266, 372). 

Most of the complexes were conveniently prepared by the reaction in ethanol of the appropriate ligand with hydrated nickel perchlorate which had sometimes been dehydrated previously by stirring it with an excess of 2,2-dimethoxypropane or triethyl orthoformate. It must be remembered that transition metal perchlorate complexes with amines are potentially hazardous and can explode even under mild conditions. Safety precautions must be used in preparations Ni(C104)2(H20)2 has been prepared by carefully heating the hexahydrate under vacuum at about 100 °C.1584... 

Jilulc HNO, and concentrating the solution. The compound deliquesces in moist air and effloresces in dry air. The pink anhydrous cobaltous nitrate cannot he formed by dehydrating Ihe hexahydrate but by treating Ihe salt with nitrogen pentoxide gas (or in solution in concentrated HNOi). The salt is used mainly in the preparation of catalysts. 

Sodium Peroxoborate. Sodium peroxoborate (sodium perborate mono-hydrate), Na2[B2(02)2(OH) ], formerly written as NaB03 > H20, is known only as a microcrystalline powder, made by dehydrating the hexahydrate. 

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