IX, A, 3 Dalburg and Pratt: Iron Ores of Bulacan 251 



Table VII. — Calculated composition of slag from Hison iron ore (unfluxed) . 



Constituent. 



Per cent. 



Silica (SiOa) 



39.2 



44.5 



2.5 



13.8 



Alumina (AI2O3) 



Lime (CaO) 



Magnesia (MgO) 



Total . 



100.0 





A slag of this composition would generally be considered 

 as undesirable for blast furnace work, and it is doubtful if it 

 could be fused at the low temperature which prevails in the 

 Bulacan furnaces. It is true, of course, that even in the absence 

 of fluxes the slag actually obtained would differ from the 

 calculated slag in composition because of the facts that (1) 

 not all the iron is reduced, (2) the reduced iron contains less 

 than 1 per cent of silicon, and (3) the ash from the excessive 

 quantity of charcoal used goes into the slag. If allowance be 

 made for the ash from 172 parts of charcoal for every 100 

 parts of ore, if 0.5 of silicon be allowed for the iron produced — 

 a proportion which to judge from the analysis of cast iron 

 in Table V is not far from representative — and if the slag 

 be assumed to contain 1 per cent of ferrous oxide, the slag 

 from Hison ore (sample 6) should have about the composition 

 shown in the following table. 



Table VIII. — Calculated composition of slag from Hison ore (sample 6) , 



modified by charcoal ash. 



Constituent. 



Per cent. 



Silica (SiOa) - 



28.4 



30.1 



1.0 



26.1 



11.0 



2.0 



1.4 



Alumina (AI2O3)* _. . -. . _ - 



Ferrous oxide (FeO) _._-._ 



Lime (CaO) _.. 



Magnesia (MgO) 1 



Potassium oxide (K2O) . -- 



Sodium oxide (Na20) . - __ . 



Total 



100.0 





" The alumina as calculated includes also the ferric oxide in the ash of the charcoal. 



Even as modified by the charcoal ash the slag is still undesir- 

 able, principally because of the high alumina, and as a matter of 

 fact is quite different from the slag actually obtained in practice. 



The composition of Bulacan slags is shown in the following 

 table. Sample 13 is an unusual slag obtained under the condi- 

 tions stated in connection with the analysis of sample 13a of 



