oxidize and the core to crumble the core sand was removed from the al casting baked at 500 u00b0 c to remove any char therefrom and fresh gelatin added thereto the new mix was used to form a second casting without the addition of any more catalyst similarly the sand removed from the second casting was used to form a third casting without the addition of more catalyst finally the sand removed from the third casting was used to make a fourth casting without the addition of more catalyst as shown in the following table the catalyst coating remained essentially with the sand grains throughout the four casting cycles for this table the amount of iron in u03bcg fe g sand was determined at the beginning i e before any casting and between each cycle by inductively coupled plasma analysis using an iron standard another test was conducted to ascertain the effect of the catalyst coating and the amount thereof needed to effectively catalyze oxidation of the binder the figure shows the results of that test more specifically the figure shows that at 500 u00b0 c and catalyst levels as low as 0 1 fe 2 o 3 about 82 to 86 of the binder had burned out in the first ten minutes of treatment compared to only 70 for sand without the catalyst coating similarly after fifteen minutes virtually all of the binder had burned out in contrast to only about 85 for the uncatalyzed sand it took about 20 minutes for all of the binder to burn out of the uncatalyzed sand visual observations confirmed these results in this regard after baking at 500 u00b0 c iron oxide catalyzed cores were remarkably less intact and consisted of more freer flowing sand within.