Nitrous oxide solutions

Following the original work of Scholes and Simic, many workers have studied the production of N2 from nitrous oxide solutions. It is now generally agreed that the results cannot be interpreted solely in terms of electron capture. Because of this and because of the general interest in this system, this solute is treated in a separate section after the concentration dependence of secondary ionic reactions is discussed. 

In the 1470-A. photolysis of cyclohexane-nitrous oxide solutions, nitrous oxide reacts with excited cyclohexane molecules to form nitrogen and oxygen atoms. The reaction of N20 with photoexcited 2,2,4-trimethylpentane molecules is much less efficient than with cyclohexane. In the radiolysis of these solutions, G(N2) is the same for different alkanes at low 5 mM) N20 concentrations. At higher concentrations, G(N2) from the radiolysis of cyclohexane is greater than G(N2) from the radiolysis of 2,2,4-trimethylpentane solutions. The N2 yields from 2,2,4-trimethylpentane are in excellent agreement with the theoretical yields of electrons expected to be scavenged by N20. The yield of N2 in the radiolysis of cyclohexane which is in excess of that formed from electrons is attributed to energy transfer from excited cyclohexane molecules to nitrous oxide. 

Table I. Photolysis of Cyclohexane-Nitrous Oxide Solutions...

Figure I. Quantum yield of nitrogen in the 1470-A. photolysis of alkane-nitrous oxide solutions at 13°C. Yields are relative to 4>(H2) = 1 for liquid cyclohexane photolysis at 1470 A. Ordinate is concentration of N20 in moles/liter...

There are several possible explanations which need to be considered for the formation of N2 in the photolysis of cyclohexane-nitrous oxide solutions. These include direct absorption of vacuum ultraviolet light by nitrous oxide, photoionization of the solvent followed by electron attachment by nitrous oxide, and reaction of nitrous oxide with either excited cyclohexene or excited cyclohexane molecules. Of these possibilities only the last explanation—reaction of excited cyclohexane molecules with nitrous oxide—is important. 

Photoionization of the hydrocarbon followed by dissociative electron attachment (Reaction 1) should be considered since the ionization potential of a molecule is less in the liquid phase than it is in the gas phase. For hydrocarbons the ionization potential is 1 to 1.5 e.v. less in the liquid phase (24). The photon energy at 1470 A. is about 1.4 e.v. below the gas-phase ionization potentials of cyclohexane and 2,2,4-trimethylpentane (14). Some ionization may therefore occur, but the efficiency of this process is expected to be low. Photoionization is eliminated as a source of N2 for the following reasons. (1) If photoionization occurred and the electron reacted with nitrous oxide, then O" would be formed. It has been shown in the radiolysis of cyclohexane-nitrous oxide solutions that subsequent reactions of O result in the formation of cyclohexene and dicyclohexyl (I, 16, 17) and very little cyclohexanol (16, Table III). In the photolysis nitrous oxide reduces the yield of cyclohexene and does not affect the yield of dicyclohexyl. This indicates that O is not formed in the photolysis, and consequently N2 does not result from electron capture. (2) A further argument against photoionization is that cyclohexane and 2,2,4-trimethylpentane have comparable gas-phase ionization potentials but exhibit quite different behavior with respect to N2 formation. 

Figure 2. Kinetic plot of Equation I for the photolysis of cyclohexane nitrous oxide solutions. Abscissa is 1 /(N2) Ordinate is 1 / [N20] in M"J...

Benzene, a known quencher of excited molecules, reduces G(N2) in cyclohexane solutions but not significantly in 2,2,4-trimethyl-pentane solutions. In the photolysis of cyclohexane, benzene reduces the extent of decomposition as a result of energy transfer, Reaction 6 (9, 25). Further, in the photolysis of cyclohexane-nitrous oxide solutions,... 

Alkaline solutions of mononitroparaffins undergo many different reactions when stored for long periods, acidified, or heated. Acidification of solutions of mononitro salts is best effected slowly at 0°C or lower with weak acids or buffered acidic mixtures, such as acetic acid—urea, carbon dioxide, or hydroxyl ammonium chloride. If mineral acids are used under mild conditions, eg, dilute HCl at 0°C, decomposition yields a carbonyl compound and nitrous oxide (Nef reaction). 

Ethylene is slightly more potent as an anesthetic than nitrous oxide, and the smell of ethylene causes choking. Diffusion through the alveolar membrane is sufficiendy rapid for equilibrium to be estabUshed between the alveolar and the pulmonary capillary blood with a single exposure. Ethylene is held both ia cells and ia plasma ia simple physical solution. The Hpoid stroma of the red blood cells absorb ethylene, but it does not combine with hemoglobin. The concentration ia the blood is 1.4 mg/mL when ethylene is used by itself for anesthesia. However, ia the 1990s it is not used as an anesthetic agent. 

Nitrous oxide [10024-97-2] M 44.0, h -88.5°. Washed with cone alkaline pyrogallol solution, to remove O2, CO2, and NO2, then dried by passage through columns of P2O5 or Drierite, and collected in a dry trap cooled in liquid N2. Further purified by ffeeze-pump-thaw and distn cycles under vacuum [Ryan and Freeman J Phys Chem 81 1455 1977],... 

As an example, consider the solubilities of the two gases, oxygen, 02, and nitrous oxide, N20, in water. The heats of solution have been measured and are as follows ... 

From the heat of solution of chlorine in water, —6.0 kcal/mole (heat evolved), how do you expect the solubility of chlorine at one atmosphere pressure and 20°C to compare with that of oxygen and of nitrous oxide, N20 ... 

The determination of magnesium in potable water is very straightforward very few interferences are encountered when using an acetylene-air flame. The determination of calcium is however more complicated many chemical interferences are encountered in the acetylene-air flame and the use of releasing agents such as strontium chloride, lanthanum chloride, or EDTA is necessary. Using the hotter acetylene-nitrous oxide flame the only significant interference arises from the ionisation of calcium, and under these conditions an ionisation buffer such as potassium chloride is added to the test solutions. 

Procedure (ii). Make certain that the instrument is fitted with the correct burner for an acetylene-nitrous oxide flame, then set the instrument up with the calcium hollow cathode lamp, select the resonance line of wavelength 422.7 nm, and adjust the gas controls as specified in the instrument manual to give a fuel-rich flame. Take measurements with the blank, and the standard solutions, and with the test solution, all of which contain the ionisation buffer the need, mentioned under procedure (i), for adequate treatment with de-ionised water after each measurement applies with equal force in this case. Plot the calibration graph and ascertain the concentration of the unknown solution. 

A double-beam atomic absorption spectrophotometer should be used. Set up a vanadium hollow cathode lamp selecting the resonance line of wavelength 318.5 nm, and adjust the gas controls to give a fuel-rich acetylene-nitrous oxide flame in accordance with the instruction manual. Aspirate successively into the flame the solvent blank, the standard solutions, and finally the test solution, in each case recording the absorbance reading. Plot the calibration curve and ascertain the vanadium content of the oil. 

In canned whipping cream, the gas nitrous oxide is used as both a propellant and a whipping agent. Nitrous oxide under pressure dissolves in the fats in the cream, and comes out of solution (like fizzing carbon dioxide in a soda) when the pressure is released. The bubbles of nitrous oxide instantly whip the cream into foam. 

If an aqueous solution of nitrourea is boiled, nitrous oxide escapes and the cyanic acid which is produced escapes in part, polymerizes in part, and in part remains in the aqueous liquid where it may react with various substances which may be introduced. If aniline is added to a saturated... 

By pulse radiolysis of nitrous oxide-saturated aqueous solutions of ferricyanide (2 X 10 " M) and various alcohols (0.1 M), Adams and Willson " were able to obtain absolute rate coefficients for the ferricyanide oxidation of the radicals derived from the alcohols by attack of the solvent irradiation product, OH-. 

Steady photoemission currents can be realized when acceptors (scavengers) for the solvated electrons are present in the solution. A good scavenger should be nonelectroactive at the potenhal of interest, should react quickly with solvated electrons, and the reaction products should be either nonelectroactive or reducible. A reachon with acceptors implies that the current of reoxidation of the solvated electrons becomes lower, and thus a steady photoemission current appears. The acceptors most often used are nitrous oxide, N2O, and hydroxonium ions, HjO. In the former case, OH radical is produced in the scavenging process, which undergoes further reduction on the electrode, thus doubling the photocurrent ... 

The complexed halide atoms are produced by high energy radiation in solutions of colloids that contain halide anions X and are saturated with nitrous oxide. Hydrated electrons formed in the radiolysis of the aqueous solvent react with NjO according to NjO -f e -f H O - Nj -t- OH -I- OH to form additional OH radicals. Ions X are oxidized by OH, the atoms X thus formed react rapidly with X to yield XJ radicals. 

The conventional selective reduction of NOx for car passengers still competes but the efficient SCR with ammonia on V205/Ti02 for stationary sources is not available for mobile sources due to the toxicity of vanadium and its lower intrinsic activity than that of noble metals, which may imply higher amount of active phase for compensation. As illustrated in Figure 10.9, such a solution does not seem relevant because a subsequent increase in vanadium enhances the formation of undesirable nitrous oxide at low temperature. Presently, various attempts for the replacement of vanadium did not succeed regarding the complete conversion of NO into N2 at low temperature. Suarez et al. [87] who investigated the reduction of NO with NH3 on CuO-supported monolithic catalysts... 

Hart and Henglein [14] also reported the sonolytic decomposition of nitrous oxide in aqueous solutions under pure argon, pure N2O and the mixture of the two gases and reported the formation of species such as N2, O2, N02 and N03 with the maximum yield being in the Ar/N20 mixture in the vol% ratio of 85 15. Although H20 is thermodynamically much more stable than N2O but they postulated that all H20 and N2O molecules in an argon bubble were converted into free radicals in the short time of adiabatic compression phase of the bubble. They proposed a series of free radical reactions for the formation of all these species in aqueous solutions. 

Hart Edwin J, Henglein Amim (1986) Sonolytic decomposition of nitrous oxide in aqueous solution. J Phys Chem 90 5992-5995... 

The dominant form is II, and this oxide reacts with water to yield a nitrous acid solution. 

Spencer and Sachs [29] determined particulate aluminium in seawater by atomic absorption spectrometry. The suspended matter was collected from seawater (at least 2 litres) on a 0.45 tm membrane filter, the filter was ashed, and the residue was heated to fumes with 2 ml concentrated hydrofluoric acid and one drop of concentrated sulfuric acid. This residue was dissolved in 2 ml 2 M hydrochloric acid and the solution was diluted to give an aluminium concentration in the range 5-50 pg/1. Atomic absorption determination was carried out with a nitrous oxide acetylene flame. The effects of calcium, iron, sodium, and sulfate alone and in combination on the aluminium absorption were studied. 

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