Pig Iron undergoes during its conversion into Wrought Iron. 169 
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 
into wrought iron. When first heated 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 time the mass gradually 
subsides; the puddler then changes his tool, and takes the 
“puddle” to gather with it the granules of malleable iron float- 
ing in the melted mass of scoria or slag. The granules or glo- 
bules 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 about 80 lbs., 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 malleable iron produced, but also the iron con- 
taining 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 during 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. 8. Its composition 
was as follows :— 
First Second 
analysis. analysis. Mean. 
Seepon oe. Se 4. 29520 2°230 2°275 
Sere «6 DE» 2), Sia 2°670 2°720 
PReapboruse( Poy +f) vis)-(% (ns, 4 0:580 0:710 0:645 
NE as ls wh iverenen') an QOL 0:288 0-301 
Manganese and aluminium ._ traces traces 
SUD rt erivivines: ae! Jey. sme 94009... 94-059... 94:059 
100:047 = 99957 +=100-000 
224 lbs. of the above pig iron were introduced at 12 o’clock, 
on the 4th of April, 1856, into a puddling furnace which had 
