Washing procedure

Methods that concentrate the sol particles but not the soluble components can be used to purify the sol by rediluting the concentrated sol with pure water and repeating the process. 

Sedimentation by gravity is generally too slow, but centrifuging permits reasonably rapid concentration of silica particles larger than about 30-50 nm. Alternatively, silica can be flocculated with divalent metal ions and the precipitate washed free of soluble salts, then peptized by removing the flocculating ion. Alexander and Her (80) used ions such as Mg , Ca +, and Ba + and removed them by ion exchange or, in the case of Ba, precipitation as the insoluble sulfate. 

Concentration by ultrafiltration or electrodecanting can also be used as part of the washing procedure. 

A variety of methods for concentrating sols are available but evaporation of water has remained the most common industrial procedure. However, with rising cost of power and steam, other known methods will no doubt be considered. 

For stable sols such as colloidal silica, forced circulation evaporators have been generally used. Special precautions must be taken not to permit the sol to become too concentrated or to reach dryness at any point on the equipment walls and especially on the heat exchange surfaces. If this occurs, a layer of hard adherent silica is built up. The problem becomes acute as the silica approaches the final high concentration with increasing sol viscosity. 

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Note 3. This washing procedure is necessary to remove the dissolved THF. 

LRC-100Finish. The use of LRC-100 flame retardant for 50/50 polyester cotton blends has been reported (144). It is a condensation product of tetrakis(hydroxymethyl)-phosphonium salt (THP salt) and A/A7,A7 -trimethylphosphoramide [6326-72-3] (TMPA). The precondensate is prepared by heating the THP salt and TMPA in a 2.3-to-l.0-mole ratio for one hour at 60—65°C. It is appUed in conjunction with urea and trimethylolmelamine in a pad-dry-cure oxidation wash procedure. Phosphoms contents of 3.5—4.0% are needed to enable blends to pass the FF 3-71 Test. 

Several washing procedures have been devised to remove water and water-soluble by-products. The most common of these procedures are noodle... 

A total volume of 2 L of hexane washes results, accompanied by the gradual precipitation of a yellow solid from the hexane washes. The acid-wash procedure frequently leads to emulsions and gunny yellow solid in both phases back-extraction of the "aqueous" layer with hexane may be necessary. 

The ionic liquid process has a number of advantages over traditional cationic polymerization processes such as the Cosden process, which employs a liquid-phase aluminium(III) chloride catalyst to polymerize butene feedstocks [30]. The separation and removal of the product from the ionic liquid phase as the reaction proceeds allows the polymer to be obtained simply and in a highly pure state. Indeed, the polymer contains so little of the ionic liquid that an aqueous wash step can be dispensed with. This separation also means that further reaction (e.g., isomerization) of the polymer s unsaturated ot-terminus is minimized. In addition to the ease of isolation of the desired product, the ionic liquid is not destroyed by any aqueous washing procedure and so can be reused in subsequent polymerization reactions, resulting in a reduction of operating costs. The ionic liquid technology does not require massive capital investment and is reported to be easily retrofitted to existing Cosden process plants. 

Unlike in the case of conventional organic solvents, most research groups prepare the ionic liquids themselves. This may be the reason why different results are sometimes obtained with the same ionic liquids. Park and Kazlauskas performed a washing procedure with aqueous sodium carbonate and found improved reaction rates, but this might also be related to a more precisely defined water content/water activity in the reaction system [22]. 

When the reaction product is soluble in water, enzyme regeneration is difficult to achieve, since the enzyme is often lost during isolation of the product. One way to overcome this problem is application of immobilised enzyme systems. The enzyme is either covalently or ionically attached to an insoluble carrier material or is entrapped in a gel. Depending on the size of the particles used, a simple filtration and washing procedure can be used to separate the immobilised enzyme from the dissolved product A well-known example of this technique is the industrial production of 6-APA. 

Any precipitate occurring during the washing procedure was removed by filtration through a small amount of Dicalite Speedex, obtained from Chemische Fabrik Schweizerhalle, Switzerland. 

Filter the wet resin and rinse with distilled water. Repeat the washing procedure until the washing water is neutral to pH paper. Rinse with three 100-ml portions of methanol. Evaporate off the remaining methanol in a rotary film evaporator under vacuum, rotating slowly at 40°C, until visibly dry. 

Place 200 g of ion exchange resin Dowex 50W-X8, 100-200 mesh, hydrogen form into a 1-L beaker and add 600 ml of 1 M hydrochloric acid solution. Allow to stand for 24 h with occasional swirling. Decant off the liquid and filter off the resin using filter funnel and paper. Place the resin in a beaker and add 600 ml of distilled water. Stand for 24 h with occasional swirling. Decant off the liquid and repeat the washing procedure until the wash water is neutral to pH paper. 

The activity of the Au/metal oxide catalysts is extremely sensitive to the method of preparation. The Au/metal oxide catalysts were prepared by the co-precipitating method [1]. During the course of this study, we have determined that the activity and the stability of the catalyst for room temperature CO oxidation were a function of Ph of the solution, temperature of precipitation, aging temperature and time, catalyst wash procedure, and calcination. 

High performance capillary electrophoresis was introduced originally as an analytical tool. Now that instruments are equipped with automated fraction collection, however, capillary electrophoresis can be used for micropreparative collection of individual peaks separated from a mixture. Using the fraction collection feature, nanomolar amounts of solute such as proteins, peptides, oligonucleotides can be collected in amounts sufficient for microsequencing. An intersample washing procedure and use of well-formed capillaries aid in the prevention of artifacts.44... 

Storage conditions for containers before use Washing procedure and pretreatment Drying conditions... 

Cautionl The washing procedure described in Note 8 should be followed carefully. On one occasion, allowing a contact time of ca. 1 hr while attempting to use a cannula filter to remove the methylene chloride led to an exothermic decomposition... 

By a traditional method, a- and /i-iononcs can be converted to ionene, catalyzed by HI along with small amounts of phosphorus. A cleaner cydization occurred by heating /i-ionone in water at 250 °C in the MBR [50]. In the workup the usual exhaustive washing procedures were unnecessary. Similarly, as mentioned above, carvacrol was prepared almost quantitatively, by isoaromatization of carvone in water at 250 °C for 10 min [47]. A conventional, literature method utilized acidic conditions, took a longer time and proceeded in lower conversion. The above examples show that elevated temperatures under neutral pH conditions can offer advantages over acidic (or basic) reagents at lower temperatures. 

Deposition of insoluble material in the pores of the catalyst by polymerization or condensation reactions, for instance. Sometimes a washing procedure regenerates the catalyst. 

The regeneration of deactivated immobilized catalysts is not as easy as with conventional supported metal catalysts, where combustion of the deposited material is frequently used. Because such a procedure would destroy the organic ligands, one must resort to washing procedures. However, when this method fails, attempts must be made to recover the metal and the ligand, and to prepare a fresh catalyst. In principle, it is possible to recover the metal complexes from physically and ionically immobilized catalysts. This can also be done from covalently bound catalysts by using an easily hydrolyzable linker. 

Retention of Macromolecules and Exogenously Supplied Radioactivity Following Fixation and Washing Procedures"... 

Inherent in all these methodologies, which measure either absolute Sr levels or strontium isotope ratios in mineralized tissue, is the assumption that diagenesis has not altered the signal since death. This has been a matter of some considerable debate (e.g., Nelson et al. 1986), but the consensus of current opinion amongst practitioners is that the repeated acid-washing procedures used remove any diagenetic mineral, because it has a higher... 

After treatment the cells are centrifuged at 70 g for 5 min, and supernatant is discarded and the cell pellet is resuspended in PBS (pH 7). This washing procedure is repeated twice, and finally the cell pellet is resuspended in CM 10. 

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