Hexahydrate complexes

Sizing chemistry is critically linked to the pH of the paper-making system, and the oldest and most established sizing system involves the use of wood resin acids and aluminium sulfate. The presence of aluminium sulfate gives rise to an acidic pH ( 4.5), because the aluminium ion in aqueous solution exists as a hexahydrated complex capable of dissociation according to the equilibria shown in equations 7.1-7.3. Further equilibria are also possible. 

The hexahydrate complex is very stable. Table 7 shows that about one third of the hexahydrate binding energy is required to remove one water molecule to form a square pyramidal pentahydrate, as illustrated in Figure 3. 

Effective force fields that include the new potential functions based on pair interaction energies are used to calculate the dehydration of hexahydrate complexes and they are compared to DFT results for the same reaction. It is concluded that the new functions may appropriately describe high temperature and low density states, where repulsive forces start to be significant in comparison to attractive forces. 

Preparative Methods readily isolated as a pale-blue hexahydrate complex from aqueous reaction of either />-toluenesulfonic acid and copper(II) carbonate or stoichiometric amounts of silver(I) p-toluenesulfonate and copper(II) chloride dihydrate. The reagent is prepared in situ via reaction of copper oxide and p-toluenesulfonic acid in refluxing CHsCN. ... 

Iron (III) chloride hexahydrate [10025-77-17, FeCl36H2 0, is a brown-yeUow to orange material that crystallizes from a solution of iron or iron salt dissolved ia hydrochloric acid that coataias an oxidant such as Cfy or nitric acid. The monoclinic crystals contain the complex salt... 

There is much discussion on the nature of the aluminum species present in slightly acidic and basic solutions. There is general agreement that in solutions below pH 4, the mononuclear Al " exists coordinated by six water molecules, ie, [ ( 20) ". The strong positive charge of the Al " ion polarizes each water molecule and as the pH is increased, a proton is eventually released, forming the monomeric complex ion [A1(0H)(H20) ]. At about pH 5, this complex ion and the hexahydrated Al " are in equal abundance. The pentahydrate complex ion may dimerize by losing two water molecules... 

Aluminum chloride hexahydrate, AIQ 6H20, manufactured from aluminum hydroxide and hydrochloric acid [7647-01-0], HQ, is used in pharmaceuticals and cosmetics as a flocculant and for impregnating textiles. Conversion of solutions of hydrated aluminum chloride with aluminum to the aluminum chlorohydroxy complexes serve as the basis of the most widely used antiperspirant ingredients (20). 

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). 

The most common plafing bath uses fluoride to complex the fin. A typical solution contains 45 g/L staimous chloride, 300 g/L nickel chloride hexahydrate, and 55 g/L ammonium bifluofide. It is operated at pH 2.0—2.5 usiag ammonium hydroxide temperature is 65—75°C and current about 200 A/m. The bath has excellent throwing power. Air agitation is avoided. The deposit is bright without additives. Anodes are cast nickel, and the fin is replenished by additions of staimous chloride. AHoy anodes of 72% fin have been used to a much lesser extent. Tia-nickel deposits are covered by ASTM (136) and ISO (137) specifications. One other bath based on pyrophosphate has appeared ia the Hterature, but does not seem to be ia commercial use. 

Complexes. Hydrates with 9, 7, 6, 5, 4, 2 moles of w are known, but only the hexahydrate, Ni(H20)6(C104)2 is of any importance. It is obtained as long green hexagonal needles, mp 209° (Ref 8), by the action of Ni sulfate on Ba perchlorate or by dissolving Ni hydroxide (Ref 14), nitrate, or carbonate (Ref 13) in dil perchloric ac followed by evapn of the soln, filtering, and drying the crysts formed. It is very sol in dimethylformamide, and its visible spectrum has been measured in this solv (Ref 10)... 

Currently the most suitable system, that will generate potentials up to -1050 mV, is the iron-triethanolamine complex prepared from either iron(II) or iron(III) salts. Using iron(III) sulphate penta- or hexahydrate, for example, dyebaths are prepared by first dissolving sodium hydroxide in a small amount of water, to which is added the triethanolamine. Hydrated iron (III) sulphate is separately dissolved in a small amount of water and then added to the alkaline triethanolamine solution until the initially precipitated iron(III) hydroxide redissolves, after which the solution is diluted to full volume to give ... 

Visible spectroscopy (Figure 1.7) shows that mannitol does not form a complex with cobalt nitrate hexahydrate in water, even when heated to reflux. This... 

Chromium(II) chloride, 6 528t, 531, 564t Chromium(III) chloride, 6 532 physical properties, 6 528t Chromium(IV) chloride, 6 535 Chromium(III) chloride hexahydrate, physical properties, 6 528t Chromium chromate coatings, 76 219—220 Chromium complexes, 9 399 Chromium compounds, 6 526-571 analytical methods, 6 547-548 economic aspects, 6 543-546 environmental concerns, 6 550—551 health and safety factors, 6 548-550 hydrolysis, equilibrium, and complex formation constants, 6 530t manufacture, 6 538-543... 

Nickel dioxide, 77 107 Nickel double salts, 77 113 Nickel electrodes, 3 430 72 216 Nickel electroplating solutions, 9 818t Nickel extraction, 70 791 Nickel ferrite brown spinel, formula and DCMA number, 7 348t Nickel fibers, 77 108 Nickel fluoride complexes, 77 111 Nickel fluoride tetrahydrate, 77 109-110 Nickel fluoroborate, 77 111 Nickel fluoroborate hexahydrate, 4 157t, 158, 159... 

Pinacol formation from ketones and aldehydes by cathodic reduction has been enhanced in the presence of Cr(II) complexes. Electrolysis of a mixture of ben-zophenone (364) and chromium chloride hexahydrate in a DMF-NaCl04 system... 

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