CHEMICAL EFFECTS OF PUDDLING. 1 27 



The iron and manganese were then collected on a filter, 

 well washed, and then dissolved in hydrochloric acid. This 

 solution was again evaporated, and heated so as to render the 

 silicic acid insoluble. 



The residue was then heated with weak hydrochloric acid, 

 and the solution filtered to separate the silica ; carbonate of 

 baryta, recently prepared, was then added to precipitate the 

 oxide of iron ; this was separated by filtration, sulphate of 

 soda and a little hydrochloric acid were added to the liquid, 

 to separate the baryta in solution, and finally the manganese 

 was precipitated by a little caustic potash, washed, dried, 

 calcined, and its amount ascertained. 



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

 the physical conditions which pig iron assumes during its 

 conversion. When first melted in a 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 called " the boil," which is pro- 

 duced, 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 

 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 separation is hastened by 

 the puddler gradually forming large masses, called balls, 

 weighing from 70 to 80 lbs., from which the scoria drains 

 out. 



This part of the operation requires great skill, as nearly 

 the whole of the carbon has been oxidized, so that if the 



