216 ANNUAL OF SCIENTIFIC DISCOVERY. 



"Wishing to make some improvements in the manufacture of iron, we care- 

 fully examined the various analyses which had been made of pig iron and 

 wrought- iron; but we found that no comparison could be made between the 

 recorded results, as the samples analyzed had been obtained from different 

 sources, and as also no detailed analysis had been published of the various 

 chemical changes which pig iron undergoes in the process of puddling, dur- 

 ing its conversion into wrought iron. We therefore decided to undertake 

 this task, with the hope of throwing some light upon this important opera- 

 tion in the manufacture of iron, and of thereby enabling practical men to 

 make those improvements in the puddling of iron which, on many accounts, 

 are so much to be desired. To closely follow the progressive changes which 

 pig iron undergoes during its conversion into wrought iron, we took samples 

 every five or ten minutes, after the pig iron had melted in the furnace. 

 These chemical actions are clearly defined in the furnace, by the peculiar 

 appearance which the mass assumes as the operation proceeds. 



It is necessary that we should describe, in a rapid manner, the physical 

 conditions which pig iron assumes during its conversion into wrought iron. 

 "When first heated in the puddling furnace, it forms a thick, pasty mass, 

 which gradually becomes thin, and as fluid as mercury. "When it has reached 

 this point, it experiences a violent agitation, technically termed the " boil," 

 which is produced, no doubt, by the oxidation of the carbon, and the escape 

 of the carbonic oxide then generated. During this period of the operation, 

 the mass swells to several times its primitive bulk, and the puddler quickly 

 agitates the melted mass, to facilitate the oxidation of the carbon. After a 

 short time the mass gradually subsides; the puddler then changes his tool, 

 and takes the "puddle," to gather with it the granules of malleable iron 

 floating in the melted mass of scoria or slag. The granules or globules of 

 iron gradually weld together, and separate from the scoria ; and this separa- 

 tion is hastened by the puddler gradually forming large masses, called balls, 

 weighing about eighty pounds, from which the scoria drains out. This part 

 of the operation requires great skill in the puddler; for nearly the whole of 

 the carbon has been oxidized; so that if the current of air is not managed 

 with great care, the iron itself is oxidized, or, as it is technically termed, 

 "burnt;" and thus not only does great loss ensue in the quantity of mallea- 

 ble iron produced, but also the iron containing a certain quantity of oxide 

 of iron, is brittle, and of bad quality. 



We shall now examine the various chemical changes which pig iron 

 undergoes diiring its conversion into wrought iron. 



The iron we took for our experiments was a good cold-blast Staffordshire 

 iron; the pig was rather gray, being of the quality used for making iron 

 wire, or a gray No. 3. Its composition was as follows : 



First analysis. Second analysis. Mean. 



Carbon,. 2320 2-230 2-275 



Silicium, 2-770 2670 2-720 



rhoephorus, 580 0-710 645 



Sulphur, 0-318 0-288 0-301 



Manganese and aluminum, traces traces 



Iron, 94-059 94-059 94059 



100-047 99-957 100-000 



Two hundred and twenty-four pounds of the above pig iron were intro- 

 duced at 12 o'clock, on the 4th of April, 18-5(3, into a puddling furnace which 



