of the Argillaceous IrojuO re. 271 



Thus, if it happen to form along with the other ingredients 

 of the ore a highly refractory compound, this will envelope the 

 reduced particles of iron, and prevent them from becoming 

 saturated with carbon. The metallic product, in such a case, 

 has more resemblance to steel or malleable iron, than to cast- 

 iron. In the same way, if the flux contain any compound 

 from which carbon, at a high temperature precipitates a body 

 that is capable of forming an alloy with iron, this circumstance 

 will materially modify the metallic product of the assay. Among 

 the most dangerous of these substances, are sulphur and the 

 saline combinations in which it forms an ingredient, such as 

 sulphate of soda, and sulphate of lime or gypsum, &c. ; or 

 phosphoric acid and its saline combinations, such as phosphate 

 of soda, or phosphate of lime, which occurs in the earth of 

 bones, in ivory black, or in animal charcoal. All of these 

 ought to be most carefully excluded from the composition of 

 the flux. The presence of any of them, even in a very minute 

 degree, would infallibly contaminate the iron with sulphur 

 or phosphorus, either of which is productive of the most 

 injurious effects to the best properties of the metal. Indeed 

 the use of borax in a flux is not altogether harmless in this 

 respect, for it must cause the metal to be alloyed, to a certain 

 extent, with boruret of iron. 



Both sulphur and phosphorus possess in a remarkable de- 

 gree, the power of augmenting the fusibility of iron. Both of 

 them also are hostile to the formation of that state of the metal 

 which is called black cast-iron. In this respect sulphur is a 

 much more energetic agent than phosphorus. It not only 

 seems to dispose the metal so strongly for fusion as to prevent 

 it from remaining long enough in the higher and hotter part 

 of the blast furnace, but also appears to destroy, to a certain 

 extent, that peculiar state of combination between iron and 

 carbon which constitutes black cast-iron. This latter fact 

 seems to be established from the circumstance, that it is both 

 extremely difficult to produce good black cast-iron from ores 

 contaminated by pyrites, and that any piece of black cast-iron 

 is readily converted into white by being fused along with a 

 little sulphur. When metal that has been melted along with 

 some sulphur is poured from the crucible, it consolidates almoiit 



