Nitrogen dioxide calculation methods

Yonezawa and collaborators (99) have reported unrestricted open-shell SCF calculations where the one-center exchange integrals were taken into account their treatment concerned allyl, vinyl, and nitrogen dioxide radicals. The one-center exchange integrals also are involved in the INDO method (85). Here, the following relationship for hyperfine splitting constants holds ... 

Figure 2.20. Transformation of silica supported dinitrosyl complexes of nickel(II) leading to formation of nitrogen dioxide and its final stabilization on the support. The picture shows the molecular structure and the spin density contours calculated with BP/DNP method of the involved species, and evolution of the X-band EPR spectra of the NiN02 Si02 complex due to spillover of the ligand (adopted from [71]).

The chemical shifts of quinazoline 1-oxide, 3-oxide, and 1,3-dioxide were reported and were correlated with 7c-charge densities at the N-oxide nitrogen atom calculated by the MO-SCF-PPP method. 

Fig. 2-20. Photodissociation coefficients for N02, HCHO, CHjCHO, and 0( D) produced from ozone, for ground-level, clear-sky conditions. Nitrogen dioxide diamonds are measurements of Madronich et al. (1983), solid points are data of Marx et al. (1984), the solid line represents calculations of Madronich et al. (1983) using the method of Isaksen et al. (1977), and the dashed line is for isotropic scattering. Formaldehyde open points are measurements of Marx el al. (1984), and the solid line represents calculations of Calvert (1980). Acetaldehyde triangles are measurements of Marx et al. (1984), and the solid line represents calculations of Meyrahn et al. (1982). Ozone solid points are measurements of Dickerson et al. (1979) and Bahe et al. (1980) normalized to 325 Dobson units of total ozone overhead, and the solid line represents calculations of Dickerson et al. (1979).

Miller and co-workers show an on-stream sampler and a portable GC system to analyze stack gases as part of the requirements of determination of particulate matter from incinerator stacks. The concentrations of carbon dioxide, oxygen, and carbon monoxide are measured and that of nitrogen is calculated by difference. This method is of higher precision and can save time and labor when compared with the Orsat analyzer method. Further, this GC system is portable and all the components are mounted on a 2 ft by 3 ft laboratory cart, which makes mobile measurements possible. A summary of some of the techniques used is presented in Table 6.2. 

The specific surface area S of the same titanium dioxide powders for which 2R values were measured in [109] (Fig. 8.3) was determined by low-temperature nitrogen adsorption by using the BET method (Fig. 8.5) [110]. The surface area ST (in m2/g) can also be calculated from the experimentally measured 2R values using equation (8.5) ... 

Total acidity (meq/g) and carboxyl groups (meq/g) were determined by the barium hydroxide method and the calcium acetate exchange method, respectively (X4). Phenolic hydroxyl groups (meq/g) were calculated as the difference between total acidity and carboxyl groups. These determinations were carried out under a nitrogen atmosphere to minimize absorption of carbon dioxide. 

McKay (1971) carried out experiments in a Loschmidt-type diffusion cell with a nine component system including nitrogen, carbon dioxide, and a number of paraffins. The experiments were carried out at the high temperatures and pressures typical of underground oil and gas reservoirs. McKay s paper includes a dimensioned drawing of the Loschmidt-type cell used for the experiment and the initial conditions for some of his experiments. Use the theory of Section 5.5 to predict the composition profiles in this system. State clearly any assumptions made in your calculations. You will need to estimate diffusion coefficients at high pressure. Consult Reid et al. (1987) for details of methods that can be used for this purpose. 

Figure 18.2 Pregi method of microanalysis. Generations of students will recall having calculated, with anxiety, molecular formulae from the masses of carbon dioxide and water trapped in the removable absorbers. In a more recent version, the reaction gases pass over copper powder to reduce the nitrogen oxides to nitrogen. Three thermal conductivity detectors (TCD) signal the presence of HjO, COj and Nj. The measurement of the three requires elements require around 10 minutes.

In Dumas original method (1840) the substance was heated with copper oxide in an atmosphere of carbon dioxide. Elemental nitrogen was partially oxidized to nitrogen oxides NO, which were subsequently reduced over copper. The nitrogen percentage was calculated from the volume of the gas released, measured with a graduated test tube. 

---