Sinter hydrates

The Bayer process results in a waste stream known as red mud , which contains considerable amounts of sodium aluminium silicates. These can be converted into ATH if the red mud is mixed with limestone and sodium carbonate and calcined, to form sodium aluminate. This is extracted into water and gibbsite then precipitated as in the Bayer process. These products are known as sinter hydrates. They are whiter than the Bayer products as the calcination destroys the organics, but they still contain similar levels of sodium. 

Other Reactions. Dry hydrated lime adsorbs halogen gases, eg, CI2 and F2, to form hypochlorites and fluorides. It reacts with hydrogen peroxide to form calcium peroxide, a rather unstable compound. At sintering temperatures, quicklime combines with iron to form dicalcium ferrite. 

Calcium Aluminate Cements. Low purity calcium aluminate [12042-78-3] cements are obtained by sintering or fusing bauxite and lime in a rotary or shaft kiln. A high purity calcium aluminate cement, 2CaO 5AI2O2, capable of withstanding service temperatures of 1750°C can be prepared by the reaction of high purity lime with calcined or hydrated alumina (see Aluminum compounds). 

The process by which porous sintered plaques are filled with active material is called impregnation. The plaques are submerged in an aqueous solution, which is sometimes a hot melt in a compound s own water of hydration, consisting of a suitable nickel or cadmium salt and subjected to a chemical, electrochemical, or thermal process to precipitate nickel hydroxide or cadmium hydroxide. The electrochemical (46) and general (47) methods of impregnating nickel plaques have been reviewed. 

An amino-formaldehyde resin or acetone-formaldehyde resin has the capability to harden in alkaline media, in contact with a cement solution with a pH of 11 to 12. The presence of sintered CaO provides the required conditions for hardening of the methylol groups of the formaldehyde resin with Ca + ions and a further simultaneous reaction of the methylol groups that formed hydrate compounds, resulting in an improved dispersion and plastification of the solution. 

The transport of many compounds takes place through interstices of polymer chains filled with aqueous medium [52], In such cases, the rate of mass transport is directly proportional to the degree of hydration of the membranes [53]. The most widely accepted method for determining the hydration of membranes is to equilibrate the membranes in water or buffer and weigh these membranes after blotting [54], In a newer method, the matrices to be studied are placed on a sintered glass funnel which is attached to a capillary filled with water. The absorption of water results in the movement of the capillary front [55],... 

A solution of 18 g (68 mmol) of commercial ruthenium trichloride hydrate (Johnson Matthey, 40 3% ruthenium) in a mixture of isoprene (680 mL) and 2-methoxyethanol (280 mL) is heated at reflux for 10 days under inert gas (nitrogen or argon). The purple crystalline product is collected in a medium-porosity sintered-glass funnel, washed with diethyl ether, and dried in vacuo yield 19.9 g (95%). 

Tetrasodium tris(4,4 -dicarboxylato-2,2 -bipyridine)ruthenium(II)hydrate (3) (0.2 g) is taken in a 50-mL flask containing 20 mL of distilled water. The pH of this solution is taken to 2.5 by the addition of 0.1 M HC1 or HN03, and the mixture is allowed to stand for 24 h at 0°C. The resulting precipitate is collected on a medium-porosity sintered-glass fritted filter and washed 2-3 times with pH 2.5 water. The yield is 0.13 g (88%). 

The continuous high-pressure enzyme membrane reactor [30] is shown in Figure 9.2-4. The membrane with 35 mm diameter is placed between two sintered plates and fitted in the reactor. A certain amount of the catalyst (hydrated enzyme preparation) is put in the reactor which is electrically heated, with a heating jacket, to constant temperature. The substrates and the gas are pumped into the membrane reactor with the high-pressure pump. The products and unreacted reactants are collected in the separator. The catalyst remains in the reactor (behind the membrane). 

Chromium pentaphenyl carbonate,1 [(C6H5)5Cr]2C03.6H20, occurs when the concentrated aqueous mother-liquors from the preparation of the base are exposed to the air in an ice-chest. It forms orange-coloured plates, sintering at about 108° C. and melting indefinitely at 118° to 119° C. A mono- and a di-hydrate are also known. 

The fractions which crystallize on trituration with aqueous methanol are combined and recrystallized twice from aqueous methanol to give 25-hydroxycholecalciferol hydrate yield 120 mg, MP 81°-83°C (sinters 75°C). 

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