Wet sized samples of magnetite and hematite of 150-200, 200-270, 270-400 and<400mesh sizes were rolled into green balls in a horizontal drum of 30cm inside diameter and of 10cm length. The crushing strength of the balls was determined on a balance.
It may be postulated that the fineness of ore particles is an important factor which affects the optimum moisture content as well as the crushing strength of the ball. It has been found that for finer ore particlesthe strength is higher and the critical range of optimum moisture content is narrower. The optimum moisture content for magnetite is slightly higher than that for hematite. It seems, however, that there is no substantial difference between magnetite and hematite in rolling green balls. This has been verified from the results of specific surface determination for magnetite and hematite.
It is interesting to note that the strength of the ball made from ore particles which had been treated with sodium oleate solution is appreciably lower than the strength of untreated one. This has been considered to be due to the effect of hydrophobic film of sodium - oleate on the surface of ore particles. There is also no appreciable difference between magnetite and hematite in the effects of sodium oleate treatment.
