296 retort— 1879. 



3. On the Separation of Iron and Phosphorus, specially with reference to the 

 Momifactvre of Steel. By Thomas Blaik. 



The larger proportion of iron ores raised in this and most other countries con- 

 tain so much phosphorus as to render them unsuitable for the manufacture of steel. 

 Pig irons made from pure haematite ores, containing 003 to 0-00 per cent, of 

 phosphorus, are alone suitable for this purpose. The bulk of iron made from English 

 ores contains - 50 to 1*50 per cent. 



Steel made from phosphoretic iron is excessively brittle when cold, and is, con- 

 sequently, unsuited for most purposes. In a high-class steel the phosphorus should 

 never reach 0-10 per cent. ; but in second qualities it is not unusual to find 0-20 

 or 0-25 per cent. 



As the removal of this objectionable element is very necessary, numerous 

 attempts have been made to eliminate it in the various stages of the manufacture 

 of iron and steel. 



M. Jacobi based a process for removing phosphorus from ores containing it as 

 calcium-phosphate, on the fact that this salt is soluble in an aqueous solution of 

 sulphurous acid gas; but although he effected this removal commercially, the 

 process was impracticable, owing to the circumstance that it was necessary to 

 pulverise the ore, thereby unfitting it for exclusive use in the blast furnace. 



The action of the smelting operation is such that not only is all the iron reduced, 

 but also other elements, notably phosphorus, silicon, sulphur, carbon, and man- 

 ganese ; and it is only during disordered working, when oxide of iron is beino- 

 slagged off, that any of the phosphorus existing in the mineral is removed. In the 

 earlier davs of iron smelting, when the furnaces used were very imperfect, it was 

 possible to make excellent iron from ores which now give a very inferior product 

 in the modern furnace, owing to this fact. 



No method has as yet been discovered by which phosphorus and iron can be 

 separated during smelting. 



Up to the time of Bessemer's invention pig-iron was usually purified in the 

 puddling process, the principle of which is the washing out of phosphide of iron by 

 intimate contact with fused oxide of iron. Silicon and carbon are also removed, 

 and wrought-iron of good quality can be made by this process from iron containing 

 much phosphorus. Some of the silicon, and small quantities of phosphorus and 

 carbon, are sometimes removed previous to puddling by the action of an air blast, 

 and addition of oxide of iron, in the refinery, or ' running-out fire.' 



The Henderson process has been very successful in removing the whole of the 

 phosphorus rapidly during puddling ; it consists in the addition of fluor-spar and 

 titaniferous ore. 



In the Bessemer process the carbon and silicon are rapidly and completely 

 removed, but the phosphorus actually increases in quantity, or rather becomes con- 

 centrated, since the iron is to some extent oxidized, while the phosphorus remains 

 unattached. The siliceous lining of the converter forbids the existence of a basic 

 slag, which is the condition necessary for its removal. 



In the Siemens' process the same state of things exists, and since the greater 

 proportion of the steel made in the world is the product of these two processes, it 

 will be readily seen that the use of phosphoretic irons is very necessary, and in fact, 

 is now a burning question since many articles formerly made of puddled iron, such 

 as rails, are now made of steel. Iron ores suitable for puddled iron are consequently 

 unfitted for the production of iron for steel-making. 



The first process suggested for the rapid removal of phosphorus was that of 

 Mr. Isaac Lowthian Bell, who proposed to wash the molten pig-iron with a lar°-e 

 quantity of molten oxide of iron. By this means he succeeded in removing as 

 much as 90 per cent, of the phosphorus. 



Krupp's process consists in forming a thick coating of manganiferous iron ore 

 on the bottom of a Pernot-Siemens furnace, and melting pig-iron thereon. It is 

 stated that good results have been arrived at by this method. 



The use of alkaline chlorides, fluorides, and other salts, have also been suc- 

 cessful, likewise the action of chlorine gas in presence of an excess of carbon. 



