Salt addition method

The salt titration method [666] is a modification of the salt addition method. A portion of salt is added to a dispersion, and the ApH is recorded. When ApH > 0, base is added to shift the pH to an even higher value. When ApH < 0, acid is added to shift the pH to an even lower value. Once a constant pH has been established, a new portion of salt is added, and ApH is recorded again. The series of salt additions followed by acid or base additions is continued until ApH = 0. The advantage of the salt titration method as compared with the classical salt addition method is that only one portion of dispersion is used. Thus, PZC determination requires a smaller amount of solid and only one reaction vessel. Moreover, a series of measurements (e.g., at different temperatures or at different concentrations of a nonaqueous co-solvent) can be carried out with the same portion of solid, and effects due to a difference in surface properties between different portions of solid are avoided. The number of consecutive salt additions in the salt titration method is limited, because the sensitivity of ApH to an addition of the same amount of salt decreases as the initial salt concentration increases. 

Process 2-4 is main. With an increasing concentration of alkali the rate of polymerization increases and the molecular weight decreases. The nature of hydrolyzing agent and salt additions influence the acrylamide polymerization process. Various methods of the acrylamide polymerization in the presence of alkaline agents have been reviewed [12,16,17]. 

When one of the two acids is used in excess and the pk -values of the two acids differ strongly, the salt deficit method should be used with caution. Formic add, acetic acid, propionic acid, and trifluoroacetic acid have been electrolyzed competitively in mixtures of pairs. Formic acid and trifluoroacetic acid are comparable in case of electrolysis, both are more readily electrolyzed than acetic and propionic adds. Deviations are rationalized on the basis of differences in ionization [147]. It might 1 useful in such cases to neutralize both acids completely. Sometimes one of the two acids, although being the minor component, is more favorably oxidized possibly due to preferential adsorption or its higher acidity [148]. In this case the continuous addition of the more acidic add to an excess of the weaker acid may lead to successful cross-coupling [149], The chain length of the two acids should be chosen in such a... 

The corresponding liquid-phase chemistry can be used to promote ion formation by appropriate choice of solvent and pH, salt addition to form M.Na+ or M.NH4+, and postcolumn addition of reagents. The primary applications of ESI-MS are in the biopolymer field. The phenomenon of routine multiple charging is exclusive to electrospray, which makes it a very valuable technique in the fine chemical and biochemical field, because mass spectrometers can analyse high-molecular-mass samples without any need to extend their mass range, and without any loss of sensitivity. However, with ESI, molecules are not always produced with a distribution of charge states [137], Nevertheless, this phenomenon somehow complicates the determination of the true mass of the unknown. With conventional low-resolution mass spectrometers, the true mass of the macromolecule is determined by an indirect and iterative computational method. 

Walters [24] examined the effect of chloride on the use of bromide and iodide solid state membrane electrodes, and he calculated selectivity constants. Multiple linear regression analysis was used to determine the concentrations of bromide, fluorine, and iodide in geothermal brines, and indicated high interferences at high salt concentrations. The standard curve method was preferred to the multiple standard addition method because of ... 

The present procedure is an improved modification of that described by Balaban for the corresponding perchlorate. 2,4,6-Triphenylpyrylium tetrafluoroborate has also been prepared from the corresponding tetrachloroferrate with fiuoboric acid, from acetophenone and boron trifluoride, and from acetophenone, benzaldehyde, and boron trifluoride etherate. Additional methods for the preparation of pyrylium salts have been reviewed. ... 

Ion-radical reactions require special methods to stimulate or impede them. The specificity of these methods is determined with particular properties of ion-radicals. Many ion-radical syntheses are highly selective yielding products unattainable by other methods. The aim of this chapter is to analyze the phenomena that determine the ways to optimize ion-radical reactions. This chapter considers factors governing the development of the reactions with proven ion-radical mechanisms. Two groups of optimizing factors will be discussed physical and purely chemical ones. Factors such as solvent change and salt addition are certainly in the borderline between chemical and physical effects. 

In addition to the cations diseussed above, additional salts of the monoanion 2a have been prepared by substituting various pyridinium salts for the BU4NI utilized in Seheme 2. A signifieant number of salts of 2a have also been prepared via metathesis of [Bu4N][2a] with various metal PFe salts. These methods have thus produced salts of 2a with various organometallic cations ([M(Cp )2], were M = Fe, Mn, Co, Cr). 

The addition of salts to the aqueous phase of concentrated emulsions can have profound effects on their stabilities. Water-in-oil HIPEs are generally stabilised by salt addition [10,12,13,21,80,90,112] however, the nature of the salt used was found to be important [13]. Salts which decrease the cloud point of the corresponding nonionic surfactant aqueous solutions, i.e. which have a salting-out effect, were more active. The interactions of the surfactant molecules at the oil/water interface were increased due to dehydration of the hydrophilic ethylene oxide groups on addition of salt. This was verified experimentally [113] by an ESR method, which demonstrated that the surfactant molecules at the oil/water interface become more ordered if the salt concentration is increased. 

Vickery and Vickery [9] have investigated the interference by aluminium and iron in the ion-selective electrode method for the determination of fluoride in plant extracts. They demonstrated that plant ashes may contain sufficient of these two elements to seriously interfere in the determination of fluoride when using the fluoride-selective electrode. In the presence of these metals, the known additions method gives erroneous results, as did that involving the attempted formation of complexes with ethylene diamine tetraacetic acid (disodium salt) or 1,2-cyclohexylenedinitrilotetraacetic acid. 

Nevertheless, further detailed information was unavailable on the polyimide synthesis from nylon-salt-type monomers that is referred to as salt monomer method , and this method was not really recognized as a simple synthetic method of both aromatic and aliphatic polyimides. In addition, many polyimide investigations have mainly been concentrated on aromatic polyimides, and little information is available about aliphatic polyimides [13-18] that are also potential candidates for engineering plastics. 

Wunderlich and Knochel recently published the alkylation of diaryliron compounds by alkyl iodides or benzyl chloride 1 (entry 33) [77]. The reaction works well with 98% pure FeCl2 2LiCl but not with 99.998% pure metal salt. Addition of other transition metal salts showed that nickel contained in the FeCl2 of 98% purity is the likely catalyst. Alkylarenes 3 were obtained in 65-88% yield. The method tolerates ester, nitrile, fluoride, or chloride substituents. Although the use of 5-hexenyl iodide did not provide a cyclized product, the initial formation of radicals cannot be excluded safely. 

Some degree of preliminary group-separation of the crude extracts is often advantageous, and there are several methods in use. Carbon will adsorb nucleotides, and usually leaves nucleosides, amino acids, sugars, and sugar phosphates in the solution. The nucleotides are generally eluted from the carbon with ethanolic ammonia. Nucleotides may be precipitated as barium salts by the addition of ethanol or with mercuric acetate as the mercuric salts. These methods were originally introduced by Levene and coworkers. ... 

A second major route to metal-metal complexes, related to the salt-elimination method described above, is elimination of neutral molecules with concurrent formation of metal-metal bonded complexes. Transihon metal hydrides readily undergo these dinuclear reductive elimination reactions. The oxidative addition/reductive elimination see Oxidative Addition and Reductive Elimination) reaction of molecular hydrogen is a key reachon in this area (equation 47). 

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