Precipitation product composition

Other Models. In addition to Besenhard s model, the other models were mainly modifications developed from the original Peled s concept for lithium electrode passivation, with surface reaction as the major process, and emphasis was placed upon the composition and structure of the precipitated film or the interaction between the precipitated products and the bulk electrolyte components. 

Addition of water precipitates out an oxysalt, Bi203N205 H20. The degree of hydrolysis and the product composition can vary with the amount of water and the reaction temperature... 

Well-cooled sulphuryl chloride, diluted with 15-20 vols. of chloroform, is sat. with dry ammonia, the precipitated product dissolved in water, the soln. acidified with nitric acid, and the whole of the chlorine precipitated with silver nitrate the filtered soln. is neutralized with alkali, treated with silver nitrate, and the crystalline precipitate, which consists of silver sulphimide and some other silver derivative, separated by filtration. After adding a further quantity of silver nitrate, the clear soln. is treated with alkali, when silver sul-phamide is obtained as a colourless, amorphous precipitate, which, however, is invariably mixed with some other silver compound, probably the same as that present in the silver sulphimide precipitate. In order to remove this impurity, the well-washed precipitate is treated with hydrochloric acid in quantity exactly sufficient to convert the silver into chloride, and the strongly acid soln. is neutralized with ammonia and mixed with silver nitrate, when only the silver compound of unknown composition is precipitated pure silver sulphamide can now be precipitated by adding silver nitrate and excess of ammonia, and on decomposing this compound with the necessary quantity of hydrochloric acid, a neutral or feebly acid soln. of sulphamide is obtained. Sulphamide is deposited in large, colourless crystals when its aq. soln. is evaporated over sulphuric acid under reduced press. 

Fig. 6. Variation of average product compositions obtained from precipitated catalyst P3003.24 with method of pretreatment. Reprinted by permission of the copyright holder, the American Chemical Society.

Place 3000 milliliters of 40% nitric acid into a beaker, and then gently heat this mixture to about 30 Celsius. Thereafter, carefully mix the moist filter cake, prepared at the end of step 1 to the nitric acid solution over a period of about 30 minutes, while stirring the nitric acid and keeping its temperature around 30 Celsius. Immediately after the first addition of the filter cake, nitrogen oxide gases will be evolved, followed by the formation of a foam (the foam will dissipate after about 10 minutes). After the addition, raise the temperature of the mixture to 95 Celsius, and then hold this temperature for 1 hour. After heating for 1 hour, remove the heat source and allow the reaction mixture to cool to room temperature. Note A precipitate will form. When the reaction mixture reaches room temperature, filter-off the precipitated product, wash with 300 milliliters of 2% nitric acid, and then with 600 milliliters of cold water. Then vacuum dry or air-dry the product. The result will be pale yellow crystals, well suitable for use in preparing lead styphnate, or styphnic acid compositions. 

After the war, ARGF (Arbeitsgememschaft Ruhrehemie und turgi) developed the high-load fixed-bed process. The precipitated iron catalysts used consisted of Fe (100). SiOj (25), K2O (5). and Cu (5). The typical product composition obtained was 32% gasoline, 21 % diesel fuel, and 47% higher paraffins (wax) [3]. 

The molecule under study was Pd[(dmpz)2(Hdmpz)2]2, where Hdmpz = 3,5-dimethylpyrazole, 3-XXIII. The material is trimorphic. The reaction mixture yields mostly (90 per cent) the monoclinic (C2/c, racemic) a phase, the remainder being the triclinic (PI, racemic) y phase. The latter can be removed by recrystallization from 1,2-dichloroethane, which suggests that it is the more soluble and hence, the less stable polymorph in that solvent. Masciocchi et al. (1997) found that mixtures of various amounts of a and y polymorphs could be obtained by varying the solvent and precipitation temperature (-70 °C to -1-50 °C), with a preferred at higher temperatures, consistent with the earlier observation of relative stability. Pure polymorph y may be obtained by a different synthetic route which, when employing an excess of 3,5-dimethylpyrazole, leads to an approximately 50 50 mixture of polymorphs a and y. This system thus also represents a case in which the polymorph obtained, or the polymorphic mixture obtained, depends on the synthetic route to the desired material. It is probably more correct to state that as usual, the polymorph or polymorphic mixture depends on the crystallization conditions, and these will clearly differ in the solvent/reagent/product compositions resulting from different synthetic conditions and routes. 

The technological aspects of hydrous titanium oxide production were developed in Great Britain. This product is obtained in irregular granular form by precipitation with basic titanium sulfate or chloride solutions. After the precipitation step further granulation of the precipitate is obtained using different methods. A typical product composition is 60% Ti02, 30% HjO, and 10% a mixture of other components, includ-... 

Hence, in products from D to I, which were the supernatants obtained after dilution, decantation, and centrifugation of previous products, respectively, significant drops in protein and lipid levels were observed in comparison with the initial product composition (Table 21.12). Only samples H and I had a protein level different from the other samples (Table 21.12). The decrease of protein content was of 9% and 8%, respectively, for these products. This suggests that a part of the protein in the supernatants has precipitated. This could be explained by their lower ionic strength (conductivity of 0.4—0.8 mS/cm). Products D, E, F, and G had similar protein contents. In a general manner, the acidification by EDBM followed by a dilution resulted in the preservation of more than 90% of the protein present initially. For the fat content, the more important decrease was observed for products E and F with a respective reduction of their lipid contents of 73% and 66%. In second position are products H and I with 49% and 45% respective reduction of lipids levels (Table 21.12). These different precipitation levels might be explained by the initial fat contents of the products. Effectively, products E and F obtained from samples B and C contained between 0.72% and 0.78% of fat while products H and 1 obtained from products Bi and Ci have fat levels between 0.47% and 0.55%. Samples dilution following the EDBM step resulted in a reduction of lipids from 0.78% to 0.21%, a decrease of nearly 73% of initial content in WPC lipids. It also resulted in clarified supernatants with a low level in hpids and with the majority of the proteins present initially. 

Fe-Cu-Na catalysts were prepared by coprecipitation from the iron and copper nitrates with sodium hydroxide. Sodium contents were controlled by washing the precipitates. The composite catalysts were obtained by physical mixing of equal amounts of Fe-Cu-Na oxides and zeolites. After reducing the samples in a flow of 10% H2/N2 for 6 h at 350°C, the catalysts were kept at 250°C in a flow of reaction gas under 20 atm. The reactants and products were analyzed with an online gas chromatograph system. The XRD powder patterns of the catalysts before and after the reaction were obtained with C xKa radiation at 40 kV and 30 mA on a RIGAKU X-ray diffractometer. 

Because the costs of isolation and purification of soluble enzymes are high and it is often both technically difficult and costly to recover an active form of the enzyme from product mixtures when the reaction of interest is completed, soluble enzymes are normally employed only in batch operations in which the enzymes are removed from the liquid product by precipitation. Thermal deactivation may be used instead to destroy the catalytic activity of the enzyme. Immobilization of the enzyme circumvents these difficulties because the solid phase containing the enzyme is easily recovered from the product mixture. Use of immobilized enzymes makes it possible to conduct the process in a continuous flow mode, thereby facilitating process control via manipulation of the flow rate of the process stream. One can offset losses in enzyme activity as time elapses by reducing the flow rate to maintain a constant product composition. Operation in this mode permits one to obtain more product per unit of enzyme employed. 

Figure 6 shows the FT-IR spectra of the preeursor and its calcined products. For the precursor, the spectrum shows the absorption peaks of H2O and OH group (near 3373 em ) and the COj anion (near 1581, 1384, 1092, 837, 767, 696 em ). These spectra quite similar to that of the rear-earth earbonate reported in previous works. It is known that the solution of ammonium hydrogen carbonate is an alkalescent buffering solution, with three kinds of anions formed in it. Among them, both OH and COs can form precipitates with metal anions. Thus composition of the precursor will be a result of competition between OH and COs in combination with metal eations. Because both the C03 concentration and the C03 to OH molar ratio in an AHC solution with pH=6 are very high, and the K p of hydrate is usually far more than that of eaibonate. So the formation of rear earth earbonate in AHC precipitation was always observed. It is thus supposed that Lu2(C03).3 nH20 will be most likely the precipitation products under present precipitation condition. 

The literature on hydroxyapatite is very extensive and numerous varieties have been prepared by different methods. Many of these have non-stoichiometric compositions and include calcium-deficient varieties, tricalcium phosphate hydrates and various precipitated products with Ca/P ratios between 1.3 and 2.00 (Ca/P = 1.67 theoretical). While the more impure products may contain quantities of Ca(OH)2, CaHP04 -2H20 or Ca3(P04)2, the non-stoichiometry can in many cases only be accounted for by lattice vacancies (denoted as ), or snbstitntions within the crystal lattice or on its surface. The non-stoichiometry of apatites ranains a subject of much investigation since it is related to physical as well as chanical properties. 

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