Other inorganic hydroxides

Several other hydroxides of divalent metals crystallize in the same Cdl2 type structure as brucite, notably [610] those of Ca2+,Mn2+, Fe2+, Co2+, Ni2+ and Cd2+. The rates of dehydroxylation of these solids have, how- 

Giovanoli and Briitsch [264] studied the kinetics of vacuum dehydroxylation of 7-FeO 0H(- -7 Fe203). It was not possible to demonstrate satisfactory obedience to a single kinetic expression. Microscopic examinations detected the occurrence of random nucleation over reactant surfaces and crystallographic indications of the specific structural reorganization steps, which occur at the reaction interface, are discussed. 

The dehydroxylation of 3-U02(0H)2 occurs [619] by nucleation and growth of a- and 7-UO3 at reactant surfaces. The value of E for the linear rate of interface advance in the [100] direction underwent a change at 613 K [E = 190 kJ mole-1 (573-613 K) and 122 kj mole-1 (613-673 K)]. It is suggested that bulk diffusion of water was significant in the lower of the two temperature intervals. 

The initial stage of vacuum dehydroxylation of 3-Be(OH)2 (408— 493 K) [620] was deceleratory (E 59 kj mole-1), ascribed to diffusion control. During the subsequent main stage of reaction, interface penetration (E = 115 kJ mole-1) was rate-determining. 

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Inert Gas Dilution. Inert gas dilution involves the use of additives that produce large volumes of noncombustible gases when the polymer is decomposed. These gases dilute the oxygen supply to the flame or dilute the fuel concentration below the flammability limit. Metal hydroxides, metal carbonates, and some nitrogen-producing compounds function in this way as flame retardants (see Flame retardants, antimony and other inorganic compounds). 

See chlorinated rubber Metal oxides or hydroxides See other inorganic bases... 

See Formaldehyde Magnesium carbonate hydroxide See other inorganic bases, metal oxonon-metallates... 

Trinitrohexahy dro-1,3,5 -triazine See l,3,5-Trinitrohexahydro-l,3,5-triazine Calcium hydroxide, Water See other INORGANIC BASES... 

The carbon black generated by a fire from a rubber source increases the smoke density other products are highly toxic and often corrosive. The halogens, phosphates, borates, and their acids evolved during a fire corrode metals and electrical and electronic equipment. Hence many of the fire retardants described below cannot be used in situations where the toxic gases evolved will create their own hazards. In these cases inorganic hydroxides are used, at filler-type addition levels. Aluminium hydroxide and magnesium hydroxide are used as non-toxic fire retardant systems. 

Other inorganic crystals studied by Mark and his collaborators, sometimes leading to complete structure determinations, include strontium chloride, zinc hydroxide, tin tetraiodide, potassium chlorate, potassium permanganage, and ammonium ferrocyanide. Minerals investigated by them include CaSO (anhydrite), BaSO (barite), PbSO, Fe2TiO[j (pseudobrookite), and three forms of Al2Si05 (cyanite, andalusite, and sillimanite). 

Other inorganic flume retardants include magnesium hydroxide, molybdenum oxides, and tin. 

A final example of a stereoselective heterogeneous catalytic system is the work of Laycock, Collacott, Skelton and Tchir.17 Layered double hydroxide (LDH) synthetic hydrotalcite materials were used to stereospecifically polymerize propylene oxide [PO] to crystalline isotactic and liquid atactic poly(propyleneoxide) [PPO]. These authors suggest that the LDH surface acts as other inorganic or organometallic coordination initiators or catalysts by providing specific surface orientations for propylene oxide monomer. X-ray powder diffraction showed some loss of crystallinity after calcination and X-ray photoelectron spectroscopy showed an enhancement of Mg/Al content due to restructuring of the Mg and A1 surface atoms. The surface was also rich in Cl ... 

Today, PMMA is mainly filled by silica, quartz, aluminium hydroxide and other inorganic fillers. For special uses, the polymer is cross-linked. This, together with the high molecular weight, makes regeneration as a raw material in reprocessing impossible. The feedstock recycling by pyrolysis to recover the monomer is therefore a practical way. 

Inorganic chemistry as a field of study was extremely important during the early years of the exploration and development of mineral resources. Qualitative analysis methods were developed to help identify minerals and, combined with quantitative methods, to assess their purity and value. As the industrial revolution progressed, so did the chemical industry. By the early 20th century, plants for the production of ammonia, nitric acid, sulfuric acid, sodium hydroxide, and many other inorganic chemicals produced on a large scale were common. 

Beside anydrous calcium chloride and the anhydrous sulfates, a munber of other inorganic compounds are used for drying agents. Among the more common are the solid alkali hydroxides, NaOH and KOH, the alkali carbonates, particularly potassium carbonate, and the oxides of barium and calcium. The student should read the section on drying agents on pages 357-358. 

No other inorganic ions are as generally useful for separations as hydroxide and sulfide ions. Phosphate, carbonate, and oxalate ions are often employed as precipitants for cations, but their behavior is nonselective therefore, separations must ordinarily precede their use. 

An add can be defined as a substance that produces hydrogen ions, H, in aqueous solutions. We usually write the formulas of inorganic acids with hydrogen written first. Organic acids can often be recognized by the presence of the COOH group in the formula. A base is a substance that produces hydroxide ions, OH , in aqueous solutions. A salt is a compound that contains a cation other than H and an anion other than hydroxide ion, OH , or oxide ion, (see Table 2-3 on page 55). As we will see later in this chapter, salts are formed when acids react with bases. 

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