TRANSACTIONS OF SECTION B. 297 



In 187:J Mr. G. J. Snelus pointed out that phosphorus could he eliminated by 

 the maintenance of a basic slag in the Bessemer converter. Having noticed that 

 certain kinds of magnesian limestone became indurated when tired hard, he lined 

 up a vessdl with such lime, and in it successfully dephosphorised Cleveland pig- 

 iron containing about 1-50 per cent, of phosphorus. 



Messrs. Thomas and Gilchrist have during the past year successfully worked out 

 a process which is likely to be universally adopted. It is briefly, as follows : — 



1st. A durable basic lining. 



2nd. Additions of basic material. 



3rd. Continuing the blast after the carbon has been fully oxidized, for the pur- 

 pose of scorifying phosphorus. 



Bricks of the following composition are made by firing at a temperature nearly 

 equal to the melting point of platinum, and are very durable. 



Silica 9-20 



Lime 46-70 



Magnesia 32-80 



Oxide of iron, alumina, &c 11-30 



100-00 



A proper selection of the stone is all that is necessary ; the presence of silica 

 and alumina causes ' fritting,' and the bricks are very sound. Silicate of soda has 

 been used, and Mr. E. Riley has made a lining by using petroleum or kindred oils, 

 to render the lime plastic. 



The additions of magnesian limestone, with or without mixture with oxide of 

 iron, are made at the commencement of the process, resulting in the rapid removal 

 of silicon ; the carbon then commences to disappear, and when this has gone the 

 phosphorus goes. 



On the addition of spiegeleisen, the manganese, reacting on the phosphoric acid 

 contained in the slag, causes a portion of the phosphorus to return to the metal. 

 Hence the blown metal, with - 076 per cent, of phosphorus, is converted into 

 steel, with 0-177 per cent, by addition of spiegeleisen. This reaction was discovered 

 by Mr. Stead, some years ago. 



In the refining and puddling processes, as also in Bell's, the silicon and phos- 

 phorus are removed at the same time, and the carbon later, the elimination of 

 phosphorus ceasing as soon as the carbon begins to go, whereas in the Thomas 

 and Gilchrist process the carbon is all gone before the phosphorus commences to 

 scorify. M. Pourcel argues from the foregoing that a highly silicious pig would 

 be better than one low in silicon, but experience teaches that an excess of this 

 element is very undesirable, owing to the fact that the blow is prolonged, an in- 

 creased quantity of slag is made, the waste is greater, and the corrosive action of 

 the silica on the lime lining is excessive. At present, however, the presence of 

 silicon is necessary as a source of heat. Attempts have been made by Bell, Wilks, 

 and Hollway to add carbon to the bath during blowing, as a source of heat. 

 Hollway proposes to burn the flame within the vessel itself, by means of a separate 

 range of tuyeres. 



Some objections have been raised as to the commercial possibility of the manu- 

 facture of steel by such processes; these may be answered as follows: — 



1st. Every kind of pig iron made is capable of treatment. Pigs high in silicon 

 are objectionable, for the reasons previously stated. 



2nd. Operations on a large scale are even more successful than experimental 

 trials. 



3rd. The waste is found to be 17 to 18 per cent., only 2 per cent, higher than 

 in the ordinary Bessemer process. The amount of slag made is from 3£ to ft cwt. 

 per ton of pig iron used. The after-blowing is not a source of waste, inasmuch as 

 that the iron does not commence to oxidise, until practically the whole of the car- 

 bon and phosphorus are burnt out. 



4th. The corrosive action on the lining is greater than in the ordinary Bessemer 

 process, but when blowing iron low iu silicon the lining answers well. 



'c 



