in augmenting the quantity of Phosphorus in Pig-iron, 427 



As far as our experience enables us to judge, we incline to the 

 opinion that when the process of reduction is complete, or nearly 

 so, that is to say, when no oxide of iron or small quantities only 

 pass off with the slag, that then the whole of the phosphoric acid 

 IS reduced, and the phosphorus absoi-bed by the iron indepen- 

 dently of the temperature of the blast. The analyses above 

 given prove such to be the case with the iron smelted from the 

 ores ordinarily employed in this country, in which the amount 

 of phosphoric acid seldom exceeds 1 per* cent. 



With ores and scoriae containing large amounts of phosphoric 

 acid, we have also had opportunities of proving that when smelted 

 with hot-blast, all the phosphoric acid is reduced, and the phos- 

 phorus absorbed by the iron ; this we have found to be the case 

 with ores containing from 2 to 3 per cent, of phosphoric acid, 

 and with scoriae with as much as from 8 to 10 per cent ; but we 

 have not had an opportunity of examining a product smelted 

 with cold-blast from similar materials. 



The following exhibits the per-centage of phosphorus, (IX.) in 

 gray pig-iron smelted with hot-blast from pisolitic iron ore, 

 (X.) of gray pig-iron smelted with hot-blast from puddling fur- 

 nace scoriae and clay-shale : — 



IX. X 



2-56 6-94 



The slags respectively made vrith these products had the fol- 

 lowing composition : — 



IX. X. 



Silicic acid 45*64 41-n 



Alumina 10-84 9-46 



Lime 3501 37-90 



Magnesia 3-16 2*11 



Protoxide of iron . . 0-71 0*39 



Protoxide of manganese . trace 1 -61 



Sulphide of calcium . . 3-30 6-41 



Alkalies 0-82 0-71 



Phosphoric acid . . . trace trace 



Loss 0-52 0-30 



100-00 100-00 



Phosphoric acid is present in blast-furnace slags when white 

 iron is being smelted, that is, when the slag contains appreciable 

 quantities of protoxide of iron, as will be seen by the following 

 analyses. 



2F2 



