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XIX. On the Chemical Changes which Pig Iron undergoes during 
its conversion into Wrought Iron. By F. Crace Catvert, 
F.C.S., and M.R.A. of Turin ; and Ricuary Jounson, Esq.* 
\ \ J ISHING to make some improvements in the manufacture 
of iron, we carefully 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 analysed had been obtained from different sources, 
and also as no detailed analysis had been published of the 
various chemical changes which pig iron undergoes in the pro- 
cess of puddling during its conversion into wrought iron. We 
therefore decided to undertake this task, with the hope of throw- 
ing some light upon this important operation 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 fully investigate and closely follow the progressive and 
interesting chemical 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. 
Before describing the various chemical changes, the appearance 
of the melted mass as taken out of the furnace, and its chemical 
composition, we shall describe with some details the analytical 
processes which we have adopted to determine the elements 
which exist in pig and wrought iron, and in the samples taken 
during the operation. These details of analysis appear to us the 
more important, when it is remembered that most of the hete- 
rogeneous substances existing in pig iron are present only in 
minute quantities, and that it is on their gradual removal or 
decrease that the subsequent quality of the wrought iron depends. 
Also it is necessary to bear in mind, that we had to trust entirely 
to the exactitude of the analytical methods adopted, to appreciate 
the chemical changes which gradually took place in the melted 
mass during the time that the conversion of the pig iron into 
wrought iron lasted. 
Iron.—The quantity of iron was determined by dissolving 1 
gramme of iron in pure hydrochloric acid, reducing the solution 
toa perfect protosalt by a little pure zinc, and then determining 
the amount of iron by Marguerite’s process. 
Carbon.—To determine this element, we found after many 
trials that the best process was to reduce the iron into very fine 
* Communicated by the Authors. 
