250 The Philippine Journal of Science 1914 



Table VI. — Analyses of iron produced by Filipinos from Bulacan iron ores.^ 



Conetituent. 



Silicon (Si) 



Sulphur (S) 



Phosphorous 



Manganense (Mn) 



Total carbon (C) 



Graphite carbon 



Iron by difference (Fe) . 



Total 



Sample No.- 



13 A. 



Per cent. 

 1.520 

 0.044 

 0.115 

 0.101 

 5.640 

 1.600 

 92.580 



100. 000 



99. 



Per cent. 

 0.070 

 0.070 

 0.053 

 0.127 

 3.840 

 0.198 

 95. 840 



100. 



100.000 



Per cent. 

 0.620 

 0.089 

 0.130 

 0.091 

 3.790 

 0.232 

 95.280 



100. 000 



* Analyzed by T. Dar Juan, chemist, Bureau of Science. 



The statement has been very commonly made that the Bulacan 

 ores are self fluxing, and the conclusion would be natural 

 to one who made a short visit to a smelter while the furnace 

 was in blast, since there would be observed only the charging 

 of ore and fuel and the tapping of the reduced iron, with no 

 evidence of the addition of fluxes. If, however, the observer 

 has an opportunity to watch the repair of a furnace at the end of 

 a successful run, he must get an entirely different impression. 

 On blowing out, the crucible is usually found to be somewhat 

 deepened and to be enlarged at least 50 per cent in diameter; 

 moreover, throughout the smelting the clay tuyeres are gradually 

 consumed through the eating way of the hot end, and conse- 

 quently must be renewed every two to three days. The quartz- 

 sandstone block on which the blast plays is the only part of 

 the crucible which is not slagged away in considerable pro- 

 portion. It is indeed very probable that the necessity for the 

 periodic closing down of the furnace is due not alone to the 

 mechanical irregularity caused by the enlarged section of the 

 crucible but also to the circumstance that through the same cause 

 the flux which the ore demands becomes less readily available. 



That the ore does demand the addition of fluxes to form a 

 fusible slag becomes evident upon study of typical ore analyses. 

 Calculating the proportions of the principal constituents in the 

 slag which the Hison ore (analysis 6) without any flux would 

 yield, if all the iron in the ore were reduced and carried with 

 it 1 per cent of its own weight in silicon, the following result 

 would be obtained. 



