ON CAST IRON. 37 



Second Experiment ; the Fire of the Furnace being ajfijted by the Exp. II. 

 Vapour of Water. 



I had attempted to decompofe carburet ofiron in fmall quan- The carburet of 

 tities by the help of water in the ftate of vapour. By heating j,^ bAquwus 

 the carburet red hot, the water was decompofed, and I ob-v a pour. 

 tained carbonic acid gas, hidrogen gas, and oxide of iron. As 

 the chief difference between caft and malleable iron coniifts in Application of 

 a certain quantity of carburet of iron contained in the former, ^JJ""'^' to 

 and which mud be feparated to render the iron malleable, I 

 was defirous of trying the effect of water in vapour on caft 

 iron in a reverberatory furnace, principally in order to know 

 how far the refining of iron might be carried on in this way. 



About three hundred weight of caft iron of the fame quali- 

 ty as before, and juft taken from the high furnace, were put 

 into the reverberatory furnace as in the preceding experiment ; 

 we then took a large tubulated iron retort, put into it nine or Steam was in- 

 ten quarts of water, fitted a gun barrel to its neck, and intro- tr o duc ed» 

 duced the end of the gun-barrel into the little opening in the 

 furnace. The water in the retort was made to boil, fo that 

 the fteam diffufed itfelf with the flame over the melted metal. 

 At the expiration of half an hour all the marks of refining that 

 had been obferved before were perceptible ; the ebullition was by which 

 confiderable, and the flame that iflued from the chimney more p r0 ceededqu?ckp 

 bright. Two hours after the commencement of the procefsly, 

 freth water was put into the retort. In about three hours thp 

 metal began to thicken, and at the end of four hours it exhi- 

 bited the marks of refined iron, and we imagined the opera- 

 tion to be finiOied. We found the grain of this iron finer, but the iron 

 however, than that of the iron operated upon in the V^^^S^lof^kbf^' 

 experiment, and the mafs was full of little blebs. 



We gave it to the refiner, who treated it like the former ; arm was lefs 

 but to our great aftonifhment we found that it wrought worfe "|^ d e ^^"f 

 in the refinery fire than caft iron the moft difficult to refine. It fore, 

 required much more labour, and an hour's time longer. 



Having aflayed a fpecimen in the ftate in which it came out There was more 

 of the reverberatory furnace, I found it to contain a much Jar- ^arTin other'* 

 ger quantity of oxigen. Experience had already taught me, kinds of call 

 that half a pound of gray caft iron, treated in a retort with 110 "* 

 four ounces of charcoal from which all carbonic acid gas had 



been 



