396 



Calculation of the (hj/gen- Pressure, of the Dissociation- Equilibria. 

 When we know the constant of equilibrinra of an equilibrium like 



M -f CO, :;t MO + CO (3) 



resp. M + H,0 :;t iMO + H, (3a) 



and likewise the constant of equilibrium of the equilibrium: 



2C0, :;t 2C0 + 0, (4) 



resp. 2H,0^2H, + 0, (4a) 



at the same temperature, the oxygen pressure follows immediately 

 from these data. 



From (3) follows namely : 



and from (4) 



so that 

 or 



hence 



logPo, = logKp^,^^- 21ogK (5) 



In this way the oxygen pressures for the equilibria of dissociation : 



2Fe0^2Fe + 0„ 

 2Fe,0,:;t6FeO + 0, and FBjO, ^ 3Fe+ 20„ 

 have been calculated by us between 400° C. and 1000° C. 



We had to use for this an equation of log Kp for the CO, 

 dissociation equilibrium. Wishing to apply this equation for tempe- 

 ratui-es between ± 500° and ± 1000°, we have substituted the 

 heat-effect corresponding to the temperature of about 800°, viz. 

 — 133000 cal. for E in the equation: 



din Kc _ E 

 dT "" "~ RT^ ■ 

 and put SiCv =0, so on integration we got: 



133000 , ^, 



10gKe=-4^^j-7p + C (6) 



or: 



, „ 133000 



log K,, = — ^^-^ -f log T + C' .... (7) 



"Oo~ 



