Three monolithic refractories (a 90+ wt.% alumina Castable, a 50+ wt.% alumina castable, and a 90+ wt.% alumina phosphate-bonded ramming mix) doped with up to 2.0 wt.% Fe and 2.0 Fe wt.% Fe₂O₃ were tested for CO disintegration in a 100 hr. test similar to. ASTM C-288. The effects of CO₂, NH₃, H₂, H₂S, and H₂O on CO disintegration were observed. Prefired samples of all three refractories were found to be susceptible to disintegration in a CO atmosphere when 0.5 wt.% Fe or more was added. Castables doped with up to 2.0 Fe wt.% Fe₂O₃ were not affected by CO, while the ramming mix doped with 1.5 Fe wt.% Fe₂O₃ or more was. H₂ and H₂O proved most effective in retarding CO disintegration in all three refractories. CO₂, H₂S, and NH₃, in descending order, also retarded CO disintegration in both castables. The retarding effect of up to 15% CO₂ in CO is questionable for the ramming mix. NH3 did not slow CO disintegration in this refractory and H₂S actually accelerated the disintegration process. The effect of gas pressure is also found to be especially important, for it greatly accelerates CO disintegration in all three monoliths and appears to be a more significant factor than the disintegration~inhibiting gases. An optimum iron-impurity size range, neither a maximum nor a minimum, for which CO disintegration resistance was greatest was also found for the 90+ wt.% alumina castable. / Master of Science