chemical physics of discharges - Argonne National Laboratory

358
Ccxposition at the Assumed Freezing Point. The validity of this freezing
approacn can be found comparing the predicted composition at the freezing temperature
witc the sbserved composition of tne quznched gas stream. The follcwing
variaoles are defined for Table 11, whlcn facilitates the comparison.
For the equilibrium calculatians let the input stoichiometry be charac-
terized by the molar ratio CHq] /[N2 , set equal to + ; let nN21be the
number of moles of N;1 intro6uced; ani let n: be the number of moles OP
species i present at equilibrium 2t a pressure, P, and a temperature, T .
Then Tf is establisned for a given and P, as the temperature at which
equilibrium predicts the quantity nlCN/nN2 is a maximum.
Table I1 shows the mole fraction of the predominant species for a Tf value
found in an equimolar input stoichiometry. As mentioned in the "Plasma Composition"
section, above, solid-carbon formation may be retarded in this system. Therefore,
a second set of mole fraction data have been presented in Table I1 which
excludes the species C(s) from the calculation.
Table I1
Calculated Equilibrium Composition at the Temperature
where HCN Yield is Maximized
Pressure - 380 torr - 4 P [CHJ+]/ [Np] = 1.0
x2
*e
HC N
0.421
0.252
0.097
others 0.030
Including C( s)
Mole Fractions
0.543
0.283
0.109
0.038. 0.065
0.144 -
0.020
0.497
0.266
0.120
0.073
0.025
0.005
Note a: Adjusted to allow for the reactions: C2H + H - C2%, 2H - h.
0.522
0.274
0.124
0.080
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