VOL. LXXXII.] PHILOSOPHICAL TRANSACTIONS. 209 



XII. Further Observations on the Process for Changing Cast into Malleable Iron. 

 By Thomas Beddoes, M. D. p. 257- 



Since describing, (says Dr. B.) the process known among the workmen by the 

 term, puddling of iron, I have several times reconsidered the explanation of the 

 phenomena. My explanation could not indeed but be in great measure con- 

 jectural ; and subsequent reflection excited in my mind a very lively wish to 

 ascertain, in a decisive manner, the nature of the process. The following experi- 

 ments will, I flatter myself, serve to determine the degree of confidence with 

 which the principal points of my theory may be received, though they will not 

 afford a solution of all the questions which my former communication might sug- 

 gest to an acute philosopher. They were undertaken in order to ascertain, 

 1. whether any elastic fluids are really extricated during the conversion of cast 

 into malleable iron ; and 2. what is their nature; and 3. whether they vary at 

 different periods of the process, as I concluded from the appearances in the fur- 

 nace. It seemed of less consequence to ascertain their quantity. I did not how- 

 ever neglect this object of inquiry, but some very curious circumstances prevented 

 me from attaining it. 



Exper. 1. Six pounds of dark grey melting cast iron were put into an earthen 

 retort ; a glass tube was luted to the neck, and its extremity was immersed in 

 water. The retort was placed in a wind furnace. Before the retort and its con- 

 tents could be supposed to be red-hot, inflammable air came over. It burned 

 with a deep blue flame, and was in no degree explosive. It rendered lime-water 

 turbid, and was partly absorbed. When the retort had been heated about an 

 hour and half, the air, which was coming over pretty copiously, that is, at the 

 rate of 1 oz. measure every 3™, on an average, suddenly ceased, and the appara- 

 tus, on examination, proved to be no longer air-tight. The retort was found to 

 be cracked ; and the lumps of iron had none of them been melted, but they had 

 been softened, and conglutinated together. 



Exper. 2. Four ounces Troy of the same iron were put into one of Mr. 

 Wedgwood's earthen tubes, glazed and closed at one end. That end of the tube 

 was inclosed in a barrel-shaped crucible, the interstice filled with sand, and the 

 crucible reclined so as to form a very small angle with the horizon : in other re- 

 spects the apparatus was disposed as before. On the application of heat, air was 

 again extricated, sooner than I should have expected, of the same inexplosive in- 

 flammable kind. About J-th of that which came over first, and which traversed 

 the water of the receiving vessels, was absorbed by milk of lime. The residue 

 burned slowly, with a flame apparently not so deep as before the carbonic acid 

 was separated. 



In this and the former experiment, the elastic fluids were most rapidly extri- 

 cated on the first impression of a red or white heat. Afterwards they came over 



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