Nitrous oxide measurement

Walter, S., Peeken, I., Lochte, K., Webb, A., and Bange, H. W. (2005). Nitrous oxide measurements during EIFEX, the European Iron Fertilization Experiment, in the subpolar South Atlantic Ocean. Geophys. Res. Lett. 32, L 23613, doi 10.1029/2005GL024619. 

Cronn DR, Bamesberger WL, Koropalov VM. 1983. Abastumani Forest aerosol experiment (1979) Comparison to other nonurban halocarbons and nitrous oxide measurements. Environmental Science and Technology 17 383-388. 

Recommended Operating Procedure No. 56 Collection of Gaseous Grab Samples from Combustion Sources for Nitrous Oxide Measurement... 

Pierotti, D., and R. A. Rasmussen (1980). Nitrous oxide measurements in the eastern tropical Pacific Ocean. Tellus 32, 56-72. 

Rasmussen, R. A., and D. Pierotti (1978). Inter-laboratory calibration of atmospheric nitrous oxide measurements. Geophys. Res. Lett. 5, 353-355. 

Tracer Type. A discrete quantity of a foreign substance is injected momentarily into the flow stream and the time interval for this substance to reach a detection point, or pass between detection points, is measured. From this time, the average velocity can be computed. Among the tracers that have historically been used are salt, anhydrous ammonia, nitrous oxide, dyes, and radioactive isotopes. The most common appHcation area for tracer methods is in gas pipelines where tracers are used to check existing metered sections and to spot-check unmetered sections. 

Two colorimetric methods are recommended for boron analysis. One is the curcumin method, where the sample is acidified and evaporated after addition of curcumin reagent. A red product called rosocyanine remains it is dissolved in 95 wt % ethanol and measured photometrically. Nitrate concentrations >20 mg/L interfere with this method. Another colorimetric method is based upon the reaction between boron and carminic acid in concentrated sulfuric acid to form a bluish-red or blue product. Boron concentrations can also be deterrnined by atomic absorption spectroscopy with a nitrous oxide—acetjiene flame or graphite furnace. Atomic emission with an argon plasma source can also be used for boron measurement. 

The solubility coefficient S is used as a measure of water solubility. It is the ratio between the concentrations in water and air phases at equilibrium. Ethanol, a very soluble gas, has a solubility coefficient of 1 100 at, 37 C while the coefficient for nitrous oxide, a poorly soluble gas, is 0.1.5. 

Capture efficiency is the fraction of generated contaminant that is directly captured by the hood. Measurement of capture efficiency involves measuring concentration of process-generated contaminant or a tracer material. Using process-generated contaminant requires use of instruments suited to each specific contaminant and its conditions (temperature, pressure, concentration, form, etc.). In order to facilitate these measurements, a tracer is often substituted for the process-generated contaminant. The tracer is usually a gas (sulfur hexafluoride, nitrous oxide, helium, or similar), but an aerosol (particles) can also be used (potassium iodide, polystyrene particles, microbiological particles, etc.). The chosen tracer should be as similar to the real contaminant as possible, but at the same time should... 

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 ... 

Assuming the randomness factor is about the same, the gas with the larger heat effect (favoring dissolving) should have the higher solubility. The measured solubilities at one atmosphere pressure and 20°C of oxygen and nitrous oxide in water are, respectively, 02, 1.4 X 10-3 mole/liter and N20, 27 X 10-3 mole/liter, consistent with our prediction.. 

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. 

Favre and Silbermann (1852) measured the heat of combustion of carbon in nitrous oxide, and found ... 

Bronson KF, Neue HU, Singh U, Abao EB. Automated chamber measurements of methane and nitrous oxide flux in a flooded rice soil Residue, nitrogen, and water management. Soil Sci. Soc. Am. J. 1997 61 981—987. 

Sigman et al. [134] have described a bacterial method for measuring the isotopic composition of seawater nitrate at the natural-abundance level. The method is based on the analysis of nitrous oxide gas (N2O) produced quantitatively from nitrate by denitrifying bacteria. The classical denitrification pathway consists of the stepwise reduction of nitrate (NOp to nitrite (N02), nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2) ... 

This presentation covers some of the basic data and derived results are discussed. The gases species of oxygen, carbon monoxide and carbon dioxide and nitrous oxide have been measured for all the tests. In the full scale fire tests hydrogen chloride and hydrogen cyanides were measured. Hydrocarbons and their relative abundance were determined by collecting gas samples on absorbent tubes for later analysis on a gas chromatograph and a mass spectrometer. 

In the full scale fire tests some additional gaseous species were studied specifically, i.e. formaldehyde. Not all gas species were studied in every test. Hydrogen cyanide and hydrogen chloride have only been studied in situations where evolution of these species were suspected. HCN and HC1 have only been studied as collective (2, 5 or 10 minutes) samples for each fire test. It is most preferable to follow the concentrations with direct reading instruments. This has been the case for carbon monoxide, carbon dioxide, oxygen and in three out of four cases for nitrous oxide. Drager tubes were used for measurements of nitrous oxides in the DIN 53436 test. 

MgO Catalyst. A charge of 42.6 g MgO catalyst was used in this experiment and kinetic measurements were made at 409°C. The response of a MgO catalyst equilibrated with helium stream to a step inflow of nitrous oxide was followed by monitoring N2 and O2 in the downflow stream and the results were presented in Figure 6. 

The ratio, Nj/N0, can therefore be calculated. For the relatively easily excited alkali metal sodium, it is 9.9 x 10 6 at 2000 °K and 5.9 x 10 4 at 3000 °K this latter temperature is about the highest commonly obtained with flames used for atomic absorption or emission work. Hence, only about 1(T3 % of the sodium atoms are excited at 2000 ° and 6 x 1(F2 % at 3000°. For an element such as zinc,Nf/N0 is 5.4 x 10"10 at 3000 and so only 5 x 10"8% is excited. In spite of the small fraction excited, good sensitivities can be obtained for many elements by flame photometry if a high temperature flame is used, because the difference between zero and a small but finite number is measured. For example, seventy elements can be determined by flame photometry using the nitrous oxide-acetylene flame 1H. 

Refractory compounds can be determined using a nitrous oxide-acetylene flame. The formation of refractory oxides with gases in flames might not be considered an interference, since it is constant under a given set of conditions but it does decrease the sensitivity markedly so that measurement of the element may not be possible. 

Devoto 115)has described an indirect procedure for the determination of 0.1 ppm arsenic in urine. The arsenomolybdic acid complex is formed and extracted from 1 ml of urine at pH 2 into 10 ml of cyclohexanone. The molybdenum in the complex is then measured. Before extracting the arsenic, phosphate in the urine is separated by extracting the phosphomolybdic acid complex at pH 1 into isobutyl acetate. The direct determination of arsenic in biological material and blood and urine is best done using a nitrous oxide-acetylene flame 116>. The background absorption by this flame is low at 1937 A, and interferences are minimized due to the high temperature of the flame. 

Adipic acid is of considerable importance since it is a precursor to nylon and polyester, which are extensively used in many products. Between two and three million tonnes are produced worldwide each year. Currently, its main method of manufacture is a costly, multistep process involving concentrated nitric acid. Nitrous oxide is produced as a by-product in such quantities that they measurably contribute to global warming and ozone depletion [24], A cleaner alternative to this process is clearly highly desirable. 

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