N-gas value

The pure and mixed gas studies showed that if the value of eqn (1) is 1.1 + 0.2, then some fraction of the test animals would die. Below 0.9, no deaths would be expected and above 1.3, all the animals would be expected to die. Since the concentration-response curves for animal lethalities from smoke are very steep, it is assumed that if some percentage (not 0% or 100%) of the animals die, the experimental loading is close to the predicted LC50 value. Results using this method show good agreement (deaths of some of the animals when the N-gas values were above 0.9) and the good predictability of this approach. 

The Six- and Seven-gas models (N-gas) were empirical relationships developed to calculate the N-Gas Value, which is an index of toxicity. The Six-gas model includes terms for GO, GO2, oxygen (depletion), HCN, HCl, and HBr concentrations as well as the LG50 for selected animals exposed to the constituent components. These models are based on exposure data both for individual gases and for complex gas mixtures. In this way, the effect of synergistic or antagonistic interactions between the constituent gases in a smoke can be factored into the determination of toxicity [7, 8]. 

Figure A2.2.5 shows a sketch off(r) for Leimard-Jones pair potential. Now if AA is the excess Flelmholtz free energy relative to its ideal gas value, then (-pi4) = and AU/N= [5(pA /5V)/(5p)]. Then,...

Figure 3.7(a) shows experimental values of fj,j T obtained for N gas, while Figure 3.7(b) shows how the Joule-Thomson coefficient for N2 gas changes with pressure and temperature.2... 

It has been shown that carbon dioxide also increases the toxicity of the other gases currently included in the model. For example, the 30 minute plus 24 hour LC50 value of HCN decreases to 75 ppm and that of 02 increases to 6.6% in the presence of 5% C02. However, we empirically found that the effect of the C02 can only be added into this equation once. At this time, we have data on the effect of various concentrations of C02 on CO and only have information on the effect of 5% C02 on the other gases. Since CO is the toxicant most likely to be present in all real fires, we have included the C02 effect into the CO factor. As more information becomes available, the N-Gas equation will be changed to indicate the effect of C02 on the other gases as well. 

Most importantly, none of the methods have, been sufficiently checked to assess how well they reproduce the gas yields or even the LC50 values from the appropriate segments of real-scale fire tests. To begin this process, a comparison procedure has been developed and a few materials have been checked using the NBS bench-scale combustor and the N-gas method (14,15). 

Finally in this section, we refer to classic studies on gas phase interactions carried out with a pulsed electron beam high ion source mass spectrometer, which have yielded details of hydrogen bonding of substituted pyridinium ions to water in the gas phase (79JA1675). These measurements afford thermodynamic data for the stepwise hydration of pyridinium ions XC6H4NH(OH2)n for values of n varying between 0 and 4. The attenuation of substituent effects is much less than for aqueous solution, because although the water molecules cluster round NH in the gas phase, they cannot provide an overall solvation network, the dielectric constant of which in the liquid phase serves to reduce the influence of the substituent dipole. 

As an example take a gas in a cylindrical vessel. In addition to the energy there is one other constant of the motion the angular momentum around the cylinder axis. The 6A/-dimensional phase space is thereby reduced to subshells of 6N-2 dimensions. Consider a small sub volume in the vessel and let Y(t) be the number of molecules in it. According to III.2 Y(t) is a stochastic function, with range n = 0,1,2,. .., N. Each value Y = n delineates a phase cell ) one expects that Y(t) is a Markov process if the gas is sufficiently dilute and that pi is approximately a Poisson distribution if the subvolume is much smaller than the vessel. 

Figure 7. IR spectra (at 2.90 fim, 4.65 fim and 6.15fi m) of films collected on germanium plate from aqueous phase at 25° C, pH 5.6. Upper panel 0.075M CaCU at different pH values without DPL films. Lower panel DPL films spread on either 0.I5M NaCI or 0.0I0M CaCU. The solution, with or without the lipid film, was left to stand at room temperature for a given time. The germanium plate then was dipped through the interface four times, dried under a stream of N gas, and examined in the ATR accessory (for details, see...

Thermodynamic parameters of the ideal-gas hydrogenation reactions for hydrocarbons and fullerene C60 are presented in Table 4.5. The enthalpies of C60 hydrogenation are within (-59 to -86) kJ per mol of H2 (A//"/n). These values are closer to similar values for aromatic hydrocarbons (-68 -f -69 kJmob1) than to those for alkenes and cycloalkenes (-110 5- -119 kJmob1). This fact is probably due to conjugation of double bonds in C60 in spite of non-aromaticity of this compound. The symmetryless hydrogenation entropies ASH /n are close for hydrocarbons and C60 (Table 4.5). 

Both equations have been taken from ISO 1334431 and use LC50 values for lethality to provide reference data for the individual gases to calculate toxic potency, based on rats exposed for 30 min. The N-Gas model in Equation 17.1 assumes that only the effect of the main toxicant CO is enhanced by the increase in respiration rate caused by high C02 concentrations (expressed as a step function with one value of m and b for C02 concentrations below and another for those above 5%). 

Nyquist (45) states that the vp=0 frequencies occur at higher wavenumbers in the vapor phase than in the condensed phase. He has modified the n-constant values in (1) to better match the slightly different band positions in the gas-phase spectra. These values are shown in Table 4 together with those for the condensed phase. 

Ostergaard and Michelsen104 measured the gas holdup in beds of 0.25-, 1-, and 6-mm glass particles using a radioactive tracer technique. They found that hG °c Uqg, where U0G is the superficial gas velocity, and n took values of 0.88, 0.78, and 0.93, respectively, for three particle sizes. The solid-free bubble-column gave n = 1.05. They also found that, in the solid-free system and in beds of 6-mm particles, the gas holdup decreased with increasing liquid flow rate whereas in beds of 0.25- and 1-mm particles, the gas holdup increased with increasing liquid flow rate. 

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