Potassium ions, effect

There are fewer reports of linear, acyclic, ion-binding polymers. It has been reported that poly(oxyethylene) improves the solubility of alkali metals in ethers such as tetrahydrofuran, dime thoxy ethane, and diglyme, stabilizes fluorenyl alkali metal compounds, accelerates Williamson reactions and accelerates several other nucleophilic reactions.All of these effects were attributed to the ability of poly(oxyethylene) to complex with cations in solution. Yanagida and coworkers studied the alkali metal cation complexation of poly(oxyethylene), using a picrate salt extraction technique similar to the one used by Pedersen and Frensdorff. Polymers with more than 23 oxyethylene units were effective iono-phores for potassium, with degrees of extraction (percent extracted) comparable to crown ethers. The extractability per oxyethylene unit was nearly constant, and the complex stability increased linearly with increasing numbers of repeating oxyethylene units. Seven oxyethylenes were the minimum number of repeat units necessary to bind potassium ion effectively in the aqueous phase. The less efficient extraction of short-chain poly(oxyethylene) is apparently caused by its hydrophilic character. 

Sodium sulphate crystallises out in hydrated form (common ion effect) and is filtered off on concentration, sodium dichromate is obtained. For analytical purposes, the potassium salt. K2Cr20-. is preferred potassium chloride is added and the less soluble potassium dichromate obtained. 

The metal-ion complexmg properties of crown ethers are clearly evident m their effects on the solubility and reactivity of ionic compounds m nonpolar media Potassium fluoride (KF) is ionic and practically insoluble m benzene alone but dissolves m it when 18 crown 6 is present This happens because of the electron distribution of 18 crown 6 as shown m Figure 16 2a The electrostatic potential surface consists of essentially two regions an electron rich interior associated with the oxygens and a hydrocarbon like exterior associated with the CH2 groups When KF is added to a solution of 18 crown 6 m benzene potassium ion (K ) interacts with the oxygens of the crown ether to form a Lewis acid Lewis base complex As can be seen m the space filling model of this... 

Sa.lts Salting out metal chlorides from aqueous solutions by the common ion effect upon addition of HCl is utilized in many practical apphcations. Typical data for ferrous chloride [13478-10-9] FeCl2, potassium chloride [7447-40-7] KCl, and NaCl are shown in Table 9. The properties of the FeCl2-HCL-H2 0 system are important to the steel-pickling industry (see Metal SURFACE TREATMENTS Steel). Other metal chlorides that are salted out by the addition of hydrogen chloride to aqueous solutions include those of magnesium, strontium, and barium. 

Sodium and potassium ions are actively absorbed from the intestine. As a consequence of the electrical potential caused by transport of these ions, an equivalent quantity of Cf is absorbed. The resulting osmotic effect causes absorption of water (56). 

Ammonium chloride [12125-02-9], ammonium sulfate [7783-20-2], and diammonium phosphate [7708-28-0] have also been used for shale stabilization (102,103). Ammonium ions have essentially the same effect on shales as potassium ions but use of ammonium salts is often objectionable because of the alkaline nature of the mud. In the North Sea and northern Europe, where magnesium-bearing salt formations ate encountered, magnesium chloride [7786-30-3] is used, but in the United States it is used only on a small scale. 

Potassium Phosphates. The K2O—P20 —H2O system parallels the sodium system in many respects. In addition to the three simple phosphate salts obtained by successive replacement of the protons of phosphoric acid by potassium ions, the system contains a number of crystalline hydrates and double salts (Table 7). Monopotassium phosphate (MKP), known only as the anhydrous salt, is the least soluble of the potassium orthophosphates. Monopotassium phosphate has been studied extensively owing to its piezoelectric and ferroelectric properties (see Ferroelectrics). At ordinary temperatures, KH2PO4 is so far above its Curie point as to give piezoelectric effects in which the emf is proportional to the distorting force. There is virtually no hysteresis. 

Fully hydrated potassium ion coordinates about 10-11 molecules of water, whereas sodium coordinates about 16-17 molecules [115]. The ionic mobility of potassium is about 50% greater than that of sodium. In simple terms, this means that more of the water in a potassium-catalyzed resin will be available as free water for viscosity reduction and that movement of water from a glue line into the wood will have less effect in moving the adhesive off of the glue line with it. 

There is probably no better evidence for a template effect than its application directly in the solution of a synthetic problem. Rastetter and PhiUion have utilized a substituted 19-crown-6 compound (shown below in Eq. 2.9) in the formation of macrocyclic lactones. Although there were certain experimental variations and the the possibility of intermolecular potassium ion complexation, the overall formation of lactone was favorable. 

Various other observations of Krapcho and Bothner-By are accommodated by the radical-anion reduction mechanism. Thus, the position of the initial equilibrium [Eq. (3g)] would be expected to be determined by the reduction potential of the metal and the oxidation potential of the aromatic compound. In spite of small differences in their reduction potentials, lithium, sodium, potassium and calcium afford sufficiently high concentrations of the radical-anion so that all four metals can effect Birch reductions. The few compounds for which comparative data are available are reduced in nearly identical yields by the four metals. However, lithium ion can coordinate strongly with the radical-anion, unlike sodium and potassium ions, and consequently equilibrium (3g) for lithium is shifted considerably... 

Ferrocyanide reduces persulphate, the reaction being second-order in a fairly saline medium (0.5 M K2S04) with /c2 = 3.2x 10 exp(—11.9 x lO /Hr) l.mole . sec. The rate is strongly influenced by the presence of potassium ions and this has been shown not to be merely an ionic strength effect" . Consideration of all possible modes of ion-pairing led to the conclusion that the two reactants are [K(Fe(CN)6] and [KS20g] . At zero ionic strength, E = 9.6 kcal.mole and AS = —34.7 eu. Kershaw and Prue have measured the specific effects of many other cations on the rate of this reaction. 

The different hydration numbers can have important effects on the solution behaviour of ions. For example, the sodium ion in ionic crystals has a mean radius of 0 095 nm, whereas the potassium ion has a mean radius of 0133 nm. In aqueous solution, these relative sizes are reversed, since the three water molecules clustered around the Na ion give it a radius of 0-24 nm, while the two water molecules around give it a radius of only 017 nm (Moore, 1972). The presence of ions dissolved in water alters the translational freedom of certain molecules and has the effect of considerably modifying both the properties and structure of water in these solutions (Robinson Stokes, 1955). 

Another situation is found for the Na+ ions. When the membrane is permeable to these ions, even if only to a minor extent, they will be driven from the external to the internal solution, not only by diffusion but when the membrane potential is negative, also under the effect of the potential gradient. In the end, the unidirectional flux of these ions should lead to a concentration inside that is substantially higher than that outside. The theoretical value calculated from Eq. (5.15) for the membrane potential of the Na ions is -1-66 mV. Therefore, permeabihty for Na ions should lead to a less negative value of the membrane potential, and this in turn should lead to a larger flux of potassium ions out of the cytoplasm and to a lower concentration difference of these ions. All these conclusions are at variance with experience. 

The common ion effect alters the amount of solid that will dissociate in solution. The addition of solid silver chromate to an aqueous solution of potassium chromate will affect the silver chromate s solubility because —... 

Using liposomes made from phospholipids as models of membrane barriers, Chakrabarti and Deamer [417] characterized the permeabilities of several amino acids and simple ions. Phosphate, sodium and potassium ions displayed effective permeabilities 0.1-1.0 x 10 12 cm/s. Hydrophilic amino acids permeated membranes with coefficients 5.1-5.7 x 10 12 cm/s. More lipophilic amino acids indicated values of 250 -10 x 10-12 cm/s. The investigators proposed that the extremely low permeability rates observed for the polar molecules must be controlled by bilayer fluctuations and transient defects, rather than normal partitioning behavior and Born energy barriers. More recently, similar magnitude values of permeabilities were measured for a series of enkephalin peptides [418]. 

Solutions of TKPP have been shown to have unique and advantageous properties for use in formulating a wide variety of well fluids. Its reasonable cost, worldwide availability, and nontoxic properties make it a preferred additive for use in many petroleum applications. It has been shown to be a most effective salt with respect to inhibiting hydration and swelling of clay minerals commonly encountered in drilling operations and/or reservoirs. Avoiding clay problems is the major impetus for the incorporation of potassium ions in well fluids, and the use of TKPP provides advantages over and above those available from other potassium salts. 

There are several benefits to the presence of this barrier. It protects the neurons of the CNS from fluctuations in plasma components. For example, a change in the potassium ion concentration could alter neuronal function due to its effect on membrane potential. Second, the barrier minimizes the possibility that harmful blood-borne substances reach the CNS. Finally, it prevents any blood-borne substances that could function as neurotransmitters from reaching the brain and causing inappropriate neuronal stimulation. 

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