Potassium physical constants

Colloidal potassium has recently been proved as a more active reducer than the metal that has been conventionally powdered by shaking it in hot octane (Luche et al. 1984, Chou and You 1987, Wang et al. 1994). To prepare colloidal potassium, a piece of this metal in dry toluene or xylene under an argon atmosphere is submitted to ultrasonic irradiation at ca. 10°C. A silvery blue color rapidly develops, and in a few minutes the metal disappears. A common cleaning bath (e.g., Sono-clean, 35 kHz) filled with water and crushed ice can be used. A very fine suspension of potassium is thus obtained, which settles very slowly on standing. The same method did not work in THF (Luche et al. 1984). Ultrasonic waves interact with the metal by their cavitational effects. These effects are closely related to the physical constants of the medium, such as vapor pressure, viscosity, and surface tension (Sehgal et al. 1982). All of these factors have to be taken into account when one chooses a metal to be ultrasonically dispersed in a given solvent. 

The physical constants of several other imines prepared by a similar procedure are shown in Table X. The aldimines listed in the Table can be obtained only if certain precautions are strictly observed [4b]. The method of Emerson, Hess, and Uhle [4c] could not be extended satisfactorily and the method described in Preparation 2-2 is a modification of the one described by Chancel [4d] for propylidenepropylamine. The reaction is best carried out by adding the aldehyde to the amine, without a solvent, at 0°C. When the order of addition is reversed, the yields are much lower. Potassium hydroxide is added at the end in order to remove the water formed during the reaction. The use of other drying agents such as potassium carbonate or magnesium sulfate failed to yield aldimines on distillation. The aldimines should always be distilled from fresh potassium hydroxide to yield water-white products. The aldimines are unstable and should be used within a few hours after their distillation otherwise polymeric products are obtained. 

The salt effects of potassium bromide and a series office symmetrical tetraalkylammonium bromides on vapor-liquid equilibrium at constant pressure in various ethanol-water mixtures were determined. For these systems, the composition of the binary solvent was held constant while the dependence of the equilibrium vapor composition on salt concentration was investigated these studies were done at various fixed compositions of the mixed solvent. Good agreement with the equation of Furter and Johnson was observed for the salts exhibiting either mainly electrostrictive or mainly hydrophobic behavior however, the correlation was unsatisfactory in the case of the one salt (tetraethylammonium bromide) where these two types of solute-solvent interactions were in close competition. The transition from salting out of the ethanol to salting in, observed as the tetraalkylammonium salt series is ascended, was interpreted in terms of the solute-solvent interactions as related to physical properties of the system components, particularly solubilities and surface tensions. 

During catalytic dehydrocondensation of 1,7-dihydrideorganocyclohexasiloxane with 1,4-bis(hyd-roxydimethylsilyl)benzene in the presence of potassium hydroxide, the reaction order, rate constants and activation energy were determined. Catalytic dehydrocondensation is the second order reaction. Some physical and chemical parameters of low-molecular copolymers are shown in Table 16. 

SACE makes use of electrochemical and physical phenomena to machine glass. The principle is explained in Fig. 1.1 [128]. The workpiece is dipped in an appropriate electrolytic solution (typically sodium hydroxide or potassium hydroxide). A constant DC voltage is applied between the machining tool or tool-electrode and the counter-electrode. The tool-electrode is dipped a few millimetres in the electrolytic solution and the counter-electrode is, in general, a large flat plate. The tool-electrode surface is always significantly smaller than the counter-electrode surface (by about a factor of 100). The tool-electrode is generally polarised as a cathode, but the opposite polarisation is also possible. 

J.-M. Lehn, Supmmolecular Chemistry, Institute of Physical Chemistry Publications (1993), p. 88 the equilibrium constants of the ion/ciyptand association reactions are forLi+, Na+, K+, Rb+, Cs" " (only the order of magnitude is given) 10, 10, 10 , 10, 10 . respectively. As seen, the cryptand s cavity only fits well to the potassium cation. 

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