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CARBONIFEROUS LIMESTONES 



The existence of phosphorus in this ore is not a matter of merely scientific 

 interest, but of practical importance also. Collier and Rinman assert, that the 

 "cold-short" property of iron (that is, its liability to become brittle when cold), is 

 due to the presence of the phosphoret ; while Mushet, whose knowledge of iron and 

 its properties is probably superior to that of any other writer, doubts the assertion. 

 It has, he says, been matter of common remark, that iron of the most perfect 

 quality, as the Swedish, gives out, in working, a strong phosphoric smell. And he 

 adds, that any iron can be made cold-short, by introducing into the blast furnace, 

 through the medium of the flux or otherwise, silica in excess. 



In support of this view, he remarks, in his work on iron and steel : " The flue 

 cinder of the balling furnace, which, on an average, contains thirty per cent, of 

 silica, and the flue furnace cinder of the puddling furnace, containing forty per 

 cent., while sand bottoms were in use, furnished striking illustrations of that fact. 

 At first, when these cinders, containing from forty to fifty-two per cent, of iron, 

 were returned to be smelted for the production of forge pigs, the brittleness of the 

 iron was so much increased, that fears were entertained as to the practicability of 

 their use, and maintaining a marketable quality of iron. The change of system 

 which took place from puddling on sand to puddling on iron bottoms, by intro- 

 ducing a less quantity of silica into the blast furnace, had a great tendency to 

 reduce this evil, and restore fibre to the bar-iron." 



And he concludes by saying : " From this fact being so clearly ascertained, we 

 obtain a clue to explain the probable cause of cold-short in iron generally, by attri- 

 buting it to a predominant quantity of silica in the ore, rather than to the existence 

 of phosphorus." 



Here is a marked difference between the opinion of so experienced a man as 

 Mushet, and the statement of Rinman, made, in the summer of 1849, to the British 

 Association, at their annual meeting ; the statement, namely, that, in every instance 

 in which Swedish iron has proved cold-short, he had been able to detect the pre- 

 sence of phosphorus. 



To this important subject I invite the attention of American chemists and iron- 

 masters. It is only by careful chemical analysis, conducted after the most approved 

 method, that this moot point can be finally determined. Should phosphorus 

 invariably be found in cold-short iron, while it should prove to be uniformly absent 

 in iron free from that defect, the inference will be a fair one, that phosphorus is the 

 producing cause. 



Although phosphorus has been detected, as I have shown, in these Des Moines 

 ironstones, yet, as they have not yet been worked, no practicable inference, in 

 connexion with the present inquiry, can thence be drawn.* 



Many of the carbonated ironstones observed at the various localities on the Des 

 Moines, both above and below its forks, have much the same external appearance 

 as the specimen here analyzed, and will probably yield by analysis similar results, 

 being essentially carbonates of the protoxide of iron, composed of 



* The amount of phosphorus seems to vary much in different specimens. One procured below Lafayette, 

 near Dam No. 26, on the Des Moines, yielded, by analysis, the sixteenth of a per cent. only. 



