Reaction impurities

Barium fluoride [7782-32-8] Bap2, is a white crystal or powder. Under the microscope crystals may be clear and colorless. Reported melting points vary from 1290 (1) to 1355°C (2), including values of 1301 (3) and 1353°C (4). Differences may result from impurities, reaction with containers, or inaccurate temperature measurements. The heat of fusion is 28 kj/mol (6.8 kcal/mol) (5), the boiling point 2260°C (6), and the density 4.9 g/cm. The solubiUty in water is about 1.6 g/L at 25°C and 5.6 g/100 g (7) in anhydrous hydrogen fluoride. Several preparations for barium fluoride have been reported (8—10). 

Non-metallic impurities in liquid alkali metals play a major role in the corrosion of materials either by affecting metal solubilities, f orming spalli-ble corrosion products on the metal surface, promoting liquid metal embrittlement or bulk embrittlement of the surface or by sensitising the structure for further attack by other impurities e.g. O2. As in other corrosive environments the direction and magnitude of these impurity reactions... 

Impurity reactions Small amounts of impurities in the liquid phase or on the surface of the solid metal may result in the initiation of attack or in increased severity of attack by one of the mechanisms just outlined. 

The goal of Haber s research was to find a catalyst to synthesize ammonia at a reasonable rate without going to very high temperatures. These days two different catalysts are used. One consists of a mixture of iron, potassium oxide. K20, and aluminum oxide. Al203. The other, which uses finely divided ruthenium, Ru. metal on a graphite surface, is less susceptible to poisoning by impurities. Reaction takes place at 450°C and a pressure of 200 to 600 atm. The ammonia... 

Free radical polymerization Relatively insensitive to trace impurities Reactions can occur in aqueous media Can use chain transfer to solvent to modify polymerization process Structural irregularities are introduced during initiation and termination steps Chain transfer reactions lead to reduced molecular weight and branching Limited control of tacticity High pressures often required... 

However, in order to separate enantiomers via formation of diastereomers, the chiral selector (CDA) must be optically pure, e.g., 99.9% of ( )-SO, otherwise the separated diastereomeric reaction products will still be contaminated with the reaction products derived from (S)-SO, leading to optically impure reaction products (mixture of enantiomers) and false results when evaluating the optical purity data of the analyte. 

From these DSC studies together with our NMR observations from Section 3.3 we conclude (i) the peak is associated with BF3 NH2C2H5 catalyzed DDS-TGDDM impurity reactions (ii) the y peak is associated BF3 NH2C2H5 and monofluroborate catalyses of the cure reactions and (iii) the p peak is associated BF4 NH3 C2H5 cationic catalyses of the cure reactions. 

Sensitivity to the deactivating influence of impurities, reaction products or intermediates is expressed in dif-... 

The purity of silicon in this first step is only ca. 98%, and is referred to as metallurgical grade silicon (MG-Si). In order for the silicon to be used for electronics applications, additional steps are necessary to decrease the number of impurities. Reaction of MG-Si with hydrogen chloride gas at a moderate temperature converts the silicon to trichlorosilane gas (Eq. 3). When SiHCl3 is heated to a temperature of ca. 1,150°C, it decomposes into high-purity silicon and gaseous by-products (Eq.4). This reaction is typically performed in a bell-shaped Siemens-type reactor, where Si is deposited onto heated electrodes. 

Impurities, reaction and degradation products of the authorised substances are usually not evaluated unless listed in restrictions and specifications for the authorised substance. They remain the responsibility of the producer of the material and article who has to take care that they do not migrate in quantities that pose a health risk. 

Elements of Group IV clusters. Investigation of C0-02 mixtures also revealed reactions between Ol and CO. The role of impurity reactions involving H20 is considered in detail and the implications of all data to the vapour-phase radiolysis of C02 are discussed.202 A wide range of heteromolecular clusters containing CO and/or C02 together with S02, NO, or H20 has been found in isentropically expanding jets 203 the observed clusters and their formation conditions are summarized in Table 12. These clusters, particularly the hydrates, are of importance in atmospheric chemistry since favourable conditions for their formation are known to be present in jet-aircraft exhausts.203... 

So far, only the reactions with the solvent assumed to be water have been considered. However, in practical situations other components are usually simultaneously present in the solutions, including impurities, reaction products, and cosolvents. We thus need a simple method to present the equilibrium of interest. One approach to resolve this problem is the use of conditional constants originally introduced by Schwarzenbach as apparent constants and developed further by Ringbom and Kolthoff. For a simple reaction between an L(igand) and a M(etal) ion, the ML complex is formed ... 

As shown in this chapter, the solvent can influence crystal product quality through its effect on crystallization kinetics, solution thermodynamics, and crystal interface structure. However, in many instances, the presence of impurities, reaction by-products, or corrosion products in the commercial system can override the solvent-induced behavior, yielding results different from those obtained in pure solvent. The strong influence of impurities at the parts per million level stems from the unique ability of certain impurities to adsorb at key growth sites on the crystal growth surface, as discussed in detail in Section 3.6. 

A solution of a stable nitronium salt (generally the hexa-fluorophosphate N02" PFg but also the hexafluoroantimonate N02 SbFg or tetrafluoroborate N02 BFjj ) in solvents such as methylene chloride-tetramethylene sulfone, a nd the like,is reacted with the alkane (cycloalkane), with usual precautions taken to avoid moisture and other impurities. Reactions were carried out at roan temperature (25°) and in the dark in order to avoid or minimize the possibility of radical side reactions and/or proto-lytic cleavage reactions (tertiary nitroalkanes particularly undergo ready protolytic cleavage reactions). No attempt was made to optimize conditions or increase yields by raising react-... 

Alloying between liquid metal and solid metal Integranular penetration due to selective removal Impurity reactions Temperature-gradient mass transfer... 

Because of vapor pressure limitations, the Cs-Ce hydrocarbon concentrations could not be maintained at 0.0050 mol fraction without decreasing (F/Z) below 10.0 kTorr. Further research is needed to establish the Rrconcentration dependences for these species. From Tables II and III (Y4t—t) for n-C4Hio does not exhibit simple propor-tionahty to the n-C4Hio collision fraction over the mol fraction range 5 X 10" to 5 X 10 . The total hot reactivity is varying in these latter experiments, so that a nonlinear dependence is not unreasonable (7,9, 10). The results obtained at mol fractions smaller than approximately 1 X 10 , however, are suspect because of interference from H F-producing impurity reactions (5,15). 

Figure 9.15 Aqueous corrosion reactions A, electrode reactions B, deposition reactions C, impurity reactions...

Impurity reactions. Sodium can either carburize or decarburize steel, depending on the relative carbon contents of the steel and the sodium. 

Impurity Reactions. The large-scale production of molecules demands a knowledge of the fate of impurities which enter with the raw materials or are produced in the reaction steps. These impurities can cause considerable pollution and product quality problems. In many processes more equipment and energy is devoted to controlling the impurities than the main reagents and products. Figure 3 illustrates the types of reactions which could occur between impurities and other species in the reaction mixture. 

Global Atoms, Rings, Functional Groups, Competing Sites for the Desired Transform, Impurity Reactions Conditions Included... 

It has been recognized lately that, in addition to the aluminum and cobalt compounds, a substance, such as water (Sinn et al., 1961 Gippin, 1962 Cooper, 1963), may be an effective part of the catalyst system when added or present adventitiously in trace amounts. This realization of the role of a trace substance is strikingly similar to what happened years ago in the investigations of Friedel-Crafts polymerizations (Olah, 1963). At first, due to unknown impurities, reactions were observed to go, but later, as the systems were more highly purified, the reactions did not go or go as well until another catalyst component was added. 

The deterioration of physical properties of the polymer results mainly from the thermal breakdown of hydroperoxides (which is accelerated by the presence of metal ion impurities (reaction 4, Figure 1, reaction 2,... 

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