IX, A, 3 Dalburg and Pratt: Iron Ores of Bulacan 253 



The analysis of the calculated slag is far outside the limits 

 usually set for a white iron smelted with charcoal, the silica 

 being much too low and the alumina much too high. The actual 

 slag, on the other hand, conforms very closely to the well-known, 

 most fusible slag of Bodeman, which requires silica, 56 per cent; 

 alumina, 14 per cent ; and lime, 30 per cent. 



Practically the only modification required to bring the cal- 

 culated slag to conformity with the actual slag is the addition 

 of silica ; the proportion of summated lime constituents increases 

 very slightly. Thus it appears that in the smelting process as 

 practiced an ideal slag is formed automatically by the selective 

 action of the charge on the crucible walls and that silica is the 

 principal constituent so acquired. If the ore is to be smelted in 

 a permanent furnace, therefore, as several of the operators 

 desire, the flux required is not lime particularly, so long as the 

 excessive consumption of charcoal is maintained, but silica, and 

 it becomes clear from this data why the operators who have 

 recently been adding limestone to their charge have not benefited 

 thereby. It might be possible, however, to reduce the fuel con- 

 sumption somewhat by the addition of lime, because in current 

 practice fuel is demanded not only for requisite temperature 

 but also to augment the bases in the slag. 



Nothing is more evident than that the heat is insufficient in 

 the present type of furnace. The iron comes out just above the 

 freezing point, and although the slag requires silica the quartz 

 in the sandstone block which forms part of the crucible lining 

 is not attacked ; presumably the temperature is not high enough 

 to make silica in this form available. Even the fusible slags ob- 

 tained are viscous and stiff enough to cause great loss through 

 the removal of mechanically contained iron. The principal ob- 

 stacle to the attainment of a higher temperature is probably 

 the insufficiency of the blast, which is obviously lacking in volume 

 and in constancy, together with the shortness of the stack and 

 the impermeability of the burden of fine ore. 



The Bureau of Science is conducting a series of metallurgical 

 experiments on Philippine iron ores including those from Bu- 

 lacan, and will ascertain from this work just what fluxes are 

 required and in just what proportion the fluxes available are to 

 be employed with the various ores; therefore, it is not planned 

 to go further into this problem here. One thing, however, 

 should be pointed out. If the Bulacan ores are to be smelted 

 in modern furnaces with refractory linings, one of the principal 

 required fluxes for the ores now in use will be silica. Yet all 

 the furnace ores which carry silica in the form of quartz are 



