Liquid ammonia compared with water

If the oxychloride is applied in dilute benzene solution some nitrogen selenide or selenium nitride is also formed.3 With liquid ammonia in the presence of ether in open vessels, the primary product is the compound SeOCl2.4NH3, which is decomposed by water into selenium, selenium nitride, ammonium chloride, ammonium selenite and selenious acid in a sealed tube, selenium nitride is formed in comparatively good yield.4... 

As methyl alcohol freezes in the neighborhood of — 95°C, measurements at a temperature — 70°C would be comparable with water at room temperature at 25°C methyl alcohol is very unlike water, having a compressibility more than 2.5 times as large. Ethyl alcohol and liquid ammonia are likewise unsuitable for comparison with wat er. 

For highly polar media, the yield of the solvated electron can serve as a lower limit to the ionization yield. This method needs short-time measurement and may work for liquid water and ammonia. Farhataziz et al. (1974) determined the G value—that is, the 100-eV yield—of solvated electrons in liquid NH3 to be about 3.1 at -50 ns. This corresponds to a W value of 32 eV, compared with the gas-phase value of 26.5 eV. The difference may be attributed to neutralization during the intervening time. In liquid water, it has been found that G(eh) increases at short times and has a limiting value of 4.8 (Jonah et al., 1976 Sumiyoshi et al, 1985). This corresponds to W,. = 20.8 eV compared with Wgas = 30 eV (Combecher, 1980). Considering that the yield of eh can only be a lower limit of the ionization yield, suggestions have... 

There is apparently no analog of the reaction 2eh H2 in liquid ammonia, where eam is very stable. The loss of paramagnetism in concentrated solutions has been interpreted to be either by formation of (eam)2 or by association with metal cation in neither case is the spectral shift drastic. For Na in ethylenedi-amine (EDA), Dye et al. (1972) measured the rate of 2es— (es)2 as 1.7 x 109 M s-1, which is comparable to that of the corresponding reaction in water, 6 x 109 M-1s, although the products are different. A few rate constants have been measured in cesium-EDA systems, but it is not clear whether the electron or an associated form of the electron and the cation is the reactant. 

It is difficult to compare the performance of various spray towers since the type of spray distributor used influences the results. Data from Hixson and Scott 33 and others show that KGa varies as G70-8, and is also affected by the liquid rate. More reliable data with spray columns might be expected if the liquid were introduced in the form of individual drops through a single jet into a tube full of gas. Unfortunately the drops tend to alter in size and shape and it is not possible to get the true interfacial area very accurately. This has been investigated by Whitman et a/. 34 , who found that kG for the absorption of ammonia in water was about 0.035 kmol/s m2 (N/m2), compared with 0.00025 for the absorption of carbon dioxide in water. 

As compared with water, ammonia s increased ability to dissolve hydrophobic organic molecules suggests an increased difficulty in using the hydrophobic effect to generate compartmentalization in ammonia, relative to water. This in turn implies that the liposome, a compartment that works in water, generally will not work in liquid ammonia. Hydrophobic phase separation is possible in ammonia, however, albeit at lower temperatures. For example, Brunner reported that liquid ammonia and hydrocarbons form two phases, where the hydrocarbon chain contains from 1 to 36 CH2 units.5 Different hydrocarbons become miscible with ammonia at different temperatures and pressures. Thus, formation of ammonia-phobic and ammonia-philic phases, analogous to the hydrophobic and hydrophilic phases in water, useful for isolation would be conceivable in liquid ammonia at temperatures well below its boiling point at standard pressures. 

The choice of H2S rather than H2 as the circulating gas, in spite of the fact that the latter would give much higher effective separation factors, is based on the fact that to date no stable effective catalysts have been found which will catalyze the H2-H2O exchange with liquid water. The use of water vapor as in the Barr type tower makes the H2-H2O process unfavorable compared to the H2S-H2O process. Only the ammonia-hydrogen process (5) catalyzed in the liquid phase by potassium amide has emerged as competitive with the H2S-H2O exchange. A full... 

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