TRANSACTIONS OF SECTION B. 531 



oxygen in the molten iron, afTorded the necessary relief, and the operation being one 

 of extreme simplicity enables steel or wrought iron to be produced at a greatly 

 reduced cost. To such an extent has this been carried, that ore is brought by sea 

 over a distance of 1,000 miles to Middlesbrough, and from it steel rails are made 

 more cheaply than a greatly inferior article of iron can bo produced from the 

 abundant and economically wrought bed of ironstone found within a couple of 

 miles of that town. As an example of the facility of conversion may be adduced 

 the fact that the molten metal is brought direct from the blast furnace, turned 

 into steel or ingot iron as the case may be, and the heat evolved bv the operation 

 is sufficient to enable the product in many cases, without further use of fuel, to be 

 taken direct to the mill and rolled into a finished bar. 



We have just seen that •! per cent., or thereabouts, of phosphorus renders 

 steel or ingot iron valueless ; in like manner very insignificant variations in the 

 (quantities of carbon or silicon materially aftect their quality. Now the blow, as it 

 is termed, in a Bessemer converter may be accomplished in from twelve to fifteen 

 minutes. It is clear therefore that the opportunity of ascertaining the precise quality 

 of the steel is one of very short duration. It is, I think, not disputed that a pro- 

 duct can be obtained by this process possessed of very high, if indeed not of the 

 highest, excellence, but it is also pretended that the quality is not sufficiently 

 uniform for certain purposes. The ordinary reverberatory furnace is incapable of 

 atTording the necessary temperature for melting steel or wrought iron, but by 

 employing the fuel in a gaseous state, and by heating the air and gas before they 

 are brought together, as is done in the valuable furnace suggested by the Messrs. 

 Siemens, the heat is so intensified that wrought iron in it is rapidly fused. Steel 

 is now largely made in such furnaces, either by mixing wrought and cast iron, 

 as proposed by M. Pierre Martin, or by means of cast iron alone, when the carbon 

 is removed by the addition of iron ore and some limestone, in which case, by the 

 agency of the ore, the metalloids are oxidised and removed from the bath of iron. 

 Some hours being required for this, sufficient opportunity is afforded for ascertain- 

 ing the progress of the operation. 



The cause of the iron in the Siemens furnace as well as in the Bessemer con- 

 verter retaining its associated phosphorus began in time to attract tlie attention 

 of chemists. In each case the expulsion of the metalloids is effected by oxidation. 

 The carbon is gasified, and the silicium on being acidified is absorbed and forms a 

 slag containing usually 45 to 60 per cent, of silicic acid. In the presence of such 

 an excess of this substance, any phosphoric acid, if formed, could not be absorbed 

 by the slag. It was the late M. Griiner, of Paris, who, in 1867, first pointed out 

 this fact, and he it was who first recommended the use of lime in order to render 

 the slag basic instead of acid. Further, in order to avoid the presence of silica, he 

 recommended at the same time, that the converter should be lined with lime 

 instead of with fireclay. 



The same subject engaged my own attention, when guided by the fact, that as 

 oxide of iron in puddling was capable of acidifying and removing a large quantity 

 of the phosphorus as iron phosphate, it might be possible to make this removal 

 more complete by some modification in the temperature of the furnace. This was 

 found to be practicable without reducing the carbon below the point necessary for 

 the easy fusion of the metal. The result of these experiments was communicated 

 to the Iron and Steel Institute in March, 1877, when it was shown that pig-irop 

 containing l-7o per cent, of P could in a few minutes have this reduced to -2 per 

 cent. This process is now being used in the United States for freeing cast iron 

 from most of its associated phosphorus. 



The rapid destruction of the ordinary Bessemer converter led Mr. G. I. 

 Snelus to consider the practicability of using a lime lining, and on experiment- 

 ing with this on a working scale he confirmed the opinions previously 

 enunciated by Griiner by observing that the presence of lime had removed a con- 

 siderable quantity of the phosphorus. The principles involved in these discoveries 

 constitute the foundation of the very important basic process of Messrs. Thomas 

 and Gi.lchrist, which consists in adding lime to the molten steel in a converter 

 constructed on the principle described by Mr. Snelus. Considerable difficulty had, 



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