Mother solution

When pressure reaehes 6-7 bars wash water is pumped through the filter eake at a predetermined wash ratio to displaee the adhering mother solution. 

Systematic investigations of the compounds that can be precipitated by adding alkali metals fluorides to HF solutions containing tantalum or niobium are discussed in [60, 61]. Compositions of the precipitated compounds and of their corresponding mother solutions are given in Table 4. 

Equations (141) and (142) describe the equilibrium between the hydrolysis of complex fluoride acids (shift to the right) and the fluorination of hydroxides (shift to the left). Near complete precipitation of hydroxides can be achieved by applying an excessive amount of ammonia. Typically, precipitation is performed by adding ammonia solution up to pH = 8-9. However, the precipitate that separates from the mother solution can be contaminated with as much as 20% wt. fluorine [490]. Analysis of niobium hydroxides obtained under different precipitation conditions showed that the most important parameter affecting the fluorine content of the resultant hydroxide is the amount of ammonia added [490]. Sheka et al. [491] found that increasing the pH to 9.6 toward the end of the precipitation process leads to a significant reduction in fluorine content of the niobium hydroxide. 

Precipitated K—salt crystals are carefully filtrated and washed so as to separate them from the mother solution. Drying of filtrated K-salt is also a very delicate and important process that must be performed under conditions that avoid hydrolysis of the material. Potassium heptafluorotantalate is sensitive to water, basic compounds and alcohols, especially at elevated temperatures. The main product of K-salt hydrolysis is Marignac s salt. For a long time it was believed that the composition of Marignac s salt is K/Ta Fg. However, X-ray crystal structure analysis and precise chemical analysis of the... 

Atomic ratio alkaline cation/central atom (P or Si). Molar ratio precipitate HPA/initial HPA. deduced from acidimetric titration of the mother solutions. 

A mother solution of HAUCI4 (10 g/L of Au) was prepared dissolving gold powder (5g) in aqua regia (100 mL) by... 

Mother solutions of AmB were prepared in dimethylsulfoxide (DMSO) (or methanol). All drugs and lipids were stored at —20°C, protected from light. 

Above we have outlined the Importance of the structure of the crystal when we want to make a correlation between the kinetic data and the surface of all the faces. So we considered the PBC s analysis as a necessary tool to obtain the maximum of information on all sites of each crystal surface (3). The PBC s analysis specifically allows us to determine the polarity of the complementary forms. As an example we consider the complementary interface q and q (Figure 10). The two opposite interfaces show complementary behavior with respect to the hydrogen bond (HB) pointing toward the mother solution. The q interface exposes 3 HB donors and 4 acceptors whereas the opposite situation is set up on the q face. We fixed the ratio K between the number of donors and the number of acceptors over one unit cell. Hence for q face K ... 

Figure 14.3 The Genesis workstation from Tecan. (a) A general viewof the workstation. The two mobile arms move above the deck supporting the microplates, (b) A close-up view of the deck supporting the microplates, (c) The Miniprep 75 workstation is very handy when one needs to prepare crystal screening solutions from mother solutions.

Why does the intensity of the solution s colour change Filter off the precipitated crystals through a Buchner funnel. What is contained in the mother solution ... 

Investigate the mother solution for the presence of a potassium sulphate impurity . Todothis, addoneor two drops of concentrated hydrochloric acid and a solution of barium chloride to 2-3 ml of the mother solution diluted with 5-10 ml of distilled water. In a similar way, determine whether potassium sulphate is present in the separated solid potassium dichromate. Compare the results obtained. Transfer the potassium dichromate into a preliminarily weighed porcelain bowl and place it for 30-40 min into a drying cabinet (100 °C). After cooling, weigh the dichromate on a technical chemical balance. 

L-Malic acid (HOOC CH2 CHOH COOH) for use in the pharmaceutical industry is manufactured by conversion of fumaric acid by the intracellular enzyme fumarase produced by various microorganisms. The excess fumaric acid is easily separated by crystallization after concentration of the mother solution. Further addition of lime allows malic acid to be separated as calcium malate within a bioreactor crystallizer system. By adding diluted sulfuric or oxalic acid, the salt is split into free malic acid and calcium sulfate or oxalate, the latter being removed by filtration (Mourgues et al., 1997). 

What seems particularly interesting, from physicochemical point of view and in view of possible applications, is the flexibility of the structure. Depending on the composition of the mother solution, with which the solid is at equilibrium, the structure may expand or shrink preserving its main structural features (Fig. 11.11) [10],... 

Apparatus 22 is cooled with salt solution (-15 °C) to crystallise phosphonitrilechloride trimer the mixture is held for some time to let ciystals grow and precipitate. Then the ciystals are separated in centrifuge 23, and the mother solution is sent back to tank 19. The obtained crystals of phosphonitrilechloride trimer can be given additional purification, i.e. reciys-tallisation from fresh light petroleum or vacuum distillation at 127 °C and a residual pressure of 17 GPa. 

The synthesis can use mother solutions after the recrystallisation of trichlorfon. 

Reactive electrodes refer mostly to metals from the alkaline (e.g., lithium, sodium) and the alkaline earth (e.g., calcium, magnesium) groups. These metals may react spontaneously with most of the nonaqueous polar solvents, salt anions containing elements in a high oxidation state (e.g., C104 , AsF6 , PF6 , SO CF ) and atmospheric components (02, C02, H20, N2). Note that ah the polar solvents have groups that may contain C—O, C—S, C—N, C—Cl, C—F, S—O, S—Cl, etc. These bonds can be attacked by active metals to form ionic species, and thus the electrode-solution reactions may produce reduction products that are more stable thermodynamically than the mother solution components. Consequently, active metals in nonaqueous systems are always covered by surface films [46], When introduced to the solutions, active metals are usually already covered by native films (formed by reactions with atmospheric species), and then these initial layers are substituted by surface species formed by the reduction of solution components [47], In most of these cases, the open circuit potentials of these metals reflect the potential of the M/MX/MZ+ half-cell, where MX refers to the metal salts/oxide/hydroxide/carbonates which comprise the surface films. The potential of this half-cell may be close to that of the M/Mz+ couple [48],... 

There are several types of automated KF titrators available from leading companies that supply electrochemical equipment (Metrohm, for example). It should be noted that the mother solutions of these instruments are highly sensitive to side reactions with components of the nonaqueous solution. Hence, the users have to consult the suppliers of the KF mother solutions to ensure that they are compatible with the composition of the studied solution. 

Crystallization from an overall viewpoint represents transfer of a material from solution (or even a gas) to a solid phase by cooling, evaporation, or a combination of both. But there is more to it. Of considerable importance are economics, crystal size distribution, purity, and the shape of the crystals. Impurities or mother solution are carried along only in the surface or occlusions in the crystals. The partical size distribution depends on the distribution of seed crystals, which are injected into the crystallizer prior to initiation of crystallization (batch) or continuously from recycled undersized particles, the mixing in the system, the crystal growth rate, and the degree of supersaturation of the mother liquor. As in shown in the figures, both batch and continuous crystallization are used in industry. 

After solvent removal from the mother solution of re-precipitated copolymer 1 (Table 2), a semicry-stalline compound with the molecular mass equal —1100 was obtained [20, 21], The product of intra-molecular cyclization of 1,7-divinyl-1,7-dimethyloctaphenylcyclohexasiloxane and 1,3-dihydride-tetra-methyldisiloxane of the following structure only may display the current molecular mass because divinylorganocyclohexasiloxane of the tram-structure participates in formation of macromolecular chain. 

Study of the reaction (1) has indicated that at short length of linear dimethylsiloxane unit the yield of copolymers after reprecipitation is much lower. After eliminating solvent from the mother solution, a viscous product with molecular mass of 830 units was obtained. Such molecular mass can be displayed by the product of intramolecular condensation with the structure II only. To prove the possibility of forming compound with the structure II, direct synthesis of this compound was performed [21], Results of the current synthesis were also used for estimation of cis- and frara-isomers contents in the initial 1,5-dichlorohexaphenylcyclotetrasiloxane. Namely, HFC reaction of a mixture of cis- and trans-isomers of 1,5-dichlorohexaphenylcyclotetrasiloxane with 1,3-dihyd-roxytetramethyldisiloxane was studied (equimolar ratio of initial reagents, 5% anhydrous toluene so-lution, 0°C, in the presence of acceptor - pyridine). In the case of cis-isomer, formation of poly-cyclic structured compound is the most probable, whereas trans-isomers give polymeric products. The reaction proceeds in accordance with the scheme as follows ... 

Comparatively reduced yield at low lengths of dimethylsiloxane unit (n= 2, 4) in reaction (scheme 14) is explained by partial proceeding of HFC reaction by intramolecular cyclization mechanism with formation of polycyclic structures. Similar to the reaction-scheme 1 a product of intramolecular condensation was extracted from the mother solution and additionally derived by direct synthesis. 

In the standard immersion method, the dry sample is immersed in the solution (see Figure 5.15a). In a slightly different version (Rouquerol and Partyka, 1981), the sample is initially covered with the pure solvent (protected from any contact with ambient atmosphere) before receiving an appropriate dose of mother solution (see Figure 5.15b). 

As a rule, the fresh precipitates are X-ray amorphous. Crystallization is accelerated at increased temperature of the mother solution crystallization also takes place during precipitate ageing. 

A large fraction of covalent eharacter in Al-0 bonds (63 %) provides a signifieant duration of all the proeesses of the formation of aluminium hydroxide via alkaline preeipitation from salts solutions. According to NMR relaxation data, the formation of aluminium hydroxide sol proceeds from several tens minutes to hours, while aluminium hydroxide ageing under the layer of mother solution ean proeeed hours and days [38]. 

In the former case, the solid remains suspended in the liquid in the microcalorimeter cell. Then a mother solution is added, either in one step (to obtain an integral heat. A ffUnt)) or in several steps, leading to differential heats, A H(dlff)l). In the latter case one could also speak of titration calorimetry. some commercial microcalorimeters are especially constructed for such titrations. Since, with these techniques, part of the added adsorptive remains in solution, the enthalpy of dilution A yH must be subtracted it is dependent on composition and can be determined in a blank without adsorbent. The difference between A y H(int) and A y H(dlff) has been discussed before, see sec. 1.3c. 

The hydrothermal treatment is conducted under reduced basic conditions as the mother solution is diluted with water. However, a pH adjustment after dilution to a value of 10 did not show any changes in the resulting pore size enlargement. The concentration of water was found out to have a significant effect on the hydrothermal process (Tab. 2). 

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