Potassium ions, in water

The determination of potassium ions in water is carried out by AAS (method... 

When titanium dissolves in dilute hydrochloric acid, a violet solution containing titanium(III) ions is formed. This solution rapidly decolorises acidified aqueous potassium permanganate at room temperature. Titanium(IV) chloride is a colourless covalent liquid completely hydrolysed by water. Titanium(III) chloride forms hydrated titanium(III) ions in water and disproportionates when heated in a vacuum. 

The saturated solution of potassium iodate in water at 25°C has a molality equal to 0.43. Taking the activity coefficient y in this saturated solution to be 0.52, find the conventional free energy of solution at 25°C, and calculate in electron-volts per ion pair the value of L for the removal of tho ions K+ and (IOs) into water at 25°C. 

The most frequently used method for the preparation of isoquinoline Reissert compounds is treatment of an isoquinoline with acyl chloride and potassium cyanide in water or in a dichloromethane-water solvent system. Though this method could be successfully applied in a great number of syntheses, it has also some disadvantages. First, the starting isoquinoline and the Reissert compound formed in the reaction are usually insoluble in water. Second, in the case of reactive acyl halides the hydrolysis of this reaction partner may became dominant. Third, the hydroxide ion present could compete with the cyanide ion as a nucleophile to produce a pseudobase instead of Reissert compound. To decrease the pseudobase formation phase-transfer catalysts have been used successfully in the case of the dichloromethane-water solvent system, resulting in considerably increased yields of the Reissert compound. To avoid the hydrolysis of reactive acid halides in some cases nonaqueous media have been applied, e.g., acetonitrile, acetone, dioxane, benzene, while utilizing hydrogen cyanide or trimethylsilyl cyanide as reactants instead of potassium cyanide. 

Q Given that the standard enthalpy change for dissolving potassium chloride in water is - 17.0 k.l inol 1 and the standard enthalpy of formation of KCI is —436.5 kJ mol1, use the value for the enthalpy of formation of the aqueous chloride ion given in Table 2.2 to calculate a value for the enthalpy of formation of aqueous potassium ions. 

A. Potassium ion in a 250.0 ( 0.1 )-mL water sample was precipitated with sodium tetraphenylborate ... 

Physicochemical properties of L zeolites and of clinoptilolite were studied by adsorption, chromatographic, spectral, and ther-mogravimetric methods. The sodium form of L zeolite is characterized by better adsorption with respect to water and benzene vapor and by higher retention volumes of C C hydrocarbons and CO than potassium and cesium forms. The activation energy of dehydration determined by the thermogravimetric method decreases on going from the sodium to cesium form of L zeolite. When calcium is replaced by potassium ions in clinoptilolite, the latter shows a decreased adsorption with respect to water vapor. The infrared spectra of the L zeolite at different levels of hydration show the existence of several types of water with different bond characters and arrangements in the lattice. 

Potassium ions in the natural clinoptilolite (3.5-5.2%) affect adsorption only slightly with respect to water vapor. n-Hexane as well as benzene vapors are adsorbed on the secondary porous structure of the zeolite (26). 

A similar complex has been prepared with bipyrazine coligands56 by heating the dichloro-compound with potassium carbonate in water-ethanol. This complex is insoluble in organic media and its reactivity has not been reported it should be an excellent precursor to mixed chelates through the aquo ion. 

In all five simulations, no significant differences in overall RMSD were observed, suggesting that the presence or absence of potassium ions had no effect on the overall conformation of the protein. However, a distinct influence of potassium ions on the conformation of the part of the helix that acts as a selectivity filter was found. The simultaneous presence of two potassium ions stabilized the conformation observed in the X-ray structure. The potassium ions and water molecules within the pore showed a concerted movement of a water-K+-water-K+ column on a time scale of several hundred picoseconds. 

The reduction of 2-substituted-isoquinolinium salts has been reported by Torossian65 with potassium borohydride in water, by Mirza,68 and by Durmand et al.,87,68 using sodium borohydride in aqueous methanol to yield 1,2,3,4-tetrahydroisoquinolines. The reduction of the second double bond appears to arise from a mechanism similar to that leading to tetrahydropyridines from pyridinium ions (see Section I). Mirza66 (see also Bose60) found that the reduction of berberine (60) with sodium borohydride could be stopped at the 1,2-dihydro-intermediate (61), and Karrer and Brook70 showed that the 1,2-dihydroisoquinoline formed by the lithium aluminum hydride reduction of l-phenyl-2-methylisoquinolinium iodide (62) could be further reduced to the 1,2,3,4-tetrahydroisoquinoline (63) with sodium borohydride in methanol. Awe et al.71,72 and Huffman73... 

Water clusters containing simple ions are another area of current experimental and theoretical interest. Accordingly, they are also the subject of EA studies. Chaudhury et al. [113] have used EA methods on empirical potentials to obtain optimized structures of halide ions in water clusters, which they then subjected to AMI calculations for simulation of spectra. EA applications to alkali cations in TIP4P water clusters [114,115] have led to explanations of experimental mass-spectroscopic signatures of these systems, in particular the lack of magic numbers for the sodium case and some of the typical magic numbers of the potassium and cesium cases, and the role of dodecahedral clathrate structures in these species. 

Some experimental data on the product Atj are presented in Table 4.14 for solutions of potassium iodide in various solvents. Walden s rule has some rough applicability in organic solvents. When, however, the Arj products for a solute dissolved on the one hand in water and on the other in organic solvents are compared, it is found that there is considerable discrepancy (Table 4.15). This should hardly come as a surprise one should expect differences in the solvation of ions in water and in organic solvents (Section 2.20) and the resulting differences in radii of the moving ions. 

The rate of monomer consumption contains an additional contribution from initiation (see eqn 10.62). If the kinetic chains are long, this contribution is negligible, and the rate, then given by eqn 10.69, is first order in potassium amide, second order in styrene monomer, and of orders minus one in potassium ion and water. 

Many arguments are against this mechanism. As shown by Bar-Eli and Klein (1), the hydride ion from LiH is not a catalyst for this reaction. In the similar case of water, Schindewolf (16) has shown that the hydride ion does not appear in a solution of potassium hydroxide in water. The kinetic isotopic effect observed is also in contradiction to a dissociative mechanism (1). The largely negative value of the entropy of activation is an argument for a highly organized activated complex. 

Calorimeter. A differential calorimeter, operating at 25.0 °C under near-isothermal conditions, was used for all heat measurements. Similar calorimeters, designed for determining heats of ion exchange in zeolites, have been described previously (5, 6, 14, 15). The calorimeter was calibrated by measuring the heat of solution of potassium chloride in water. The ratio of the area under the curve traced by the recorder pen to the heat produced was 1.50 dz 0.04 cm per calorie. No heat could be detected when an empty evacuated bulb was broken under water. 

Growth can be assessed by measuring the content of potassium ions in the body on the following basis. Potassium ions occur mainly in infraceJJular fluids, in which the K concentration is about 142 mA4, Extracellular fluids, on the other hand, contain much lower levels of potassium, about 10 mAI. Adipose tissue is largely water free and thus contains minimal amounts of fluids and salts. The potassium ion content may be determined in growing humans. How is it possible to measure the total content of K ions in a living person A fraction of the potassium in the... 

Hydrochloric acid is secreted by parietal cells via H, K -ATPase pumps (proton pumps), of which there are more than one million per cell. The H, K -ATPase pumps utilize the phosphorylation of ATP to exchange water-solvated protons (protonated water, hydroxonium ion, H30 ) for potassium ions. In conjunction with parallel potassium and chloride ion conductances, this ATPase is responsible for the secretion of hydrochloric acid into the secretory canaliculus of the parietal cell, the enclosed space reaching a pH of near 1.0 (Rabon Reuben 1990). In the resting parietal cell, these pumps reside within the membranes of vesicles in the cell cytoplasm. When activated by histamine and gastrin, the parietal cells alter their shape and the vesicles merge with the outer cell membrane to form secretory canaliculi. 

Non-aqueous Solvation.—Structural radii and electron-cloud radii, together with lattice enthalpies and enthalpies of solvation of ionic crystals, have been reviewed.84 The free energies of transfer, AGtr(K+), of potassium ions from water to 14 non-aqueous solvents have been reported, and they were derived from measurements in an electrochemical cell assumed to have a negligible liquid-junction potential. The essentially electrostatic nature of its solvation allows K+ to be used as a model for non-specific solvent-ion interactions. A... 

Historically, water hardness was defined in terms of the capacity of cations in the water to replace the sodium or potassium ions in soaps and to form sparingly soluble products that cause scum in the sink or bathtub. Most multiply charged cations share this undesirable property. In natural waters, however, the concentrations of calcium and magnesium ions generally far exceed those of any other metal ion. Consequently, hardness is now expressed in terms of the concentration of calcium carbonate that is equivalent to the total concentration of all the multivalent cations in the sample. 

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