1080 
PROFESSOR W. N. HARTLEY OH 
An explanation of this will be facilitated by reference to three series of curves. 
The first is reduced from the analyses of Mr. G. J. Snelus, F.R.S., who gave the 
original composition of pig iron blown, and of the metal in the converter at different 
stages in the process; the second series is from the analyses made by the same 
chemist, of the gas issuing from the converter at different periods. The third series 
of curves is drawn from the analyses of metal taken from the commencement until 
the termination of the “ blow ” as quoted by Kupelwieser. The pig iron in the 
latter case was highly manganiferous. 
It will be seen from Diagram I., that the pig-iron contains very little manganese, 
and that this is oxidised immediately during the first six minutes. A small propor¬ 
tion of combined carbon is oxidised at the same time. The larger proportion, 
however, of this element is in the form of graphite, and this is converted into 
combined carbon. The combined carbon is then oxidised, and the oxidation proceeds 
with increasing rapidity. The silicon at the same time also oxidises, and the 
oxidation of the two elements proceeds together rapidly during the “ boil,” until 
during the “ fining stage ” there is little of either left. Comparing; these results with 
the composition of the issuing gas, what do we find ? First in the slag-forming 
stage, when the lines of the alkali metals are not yet visible in the spectrum, the 
carbon oxidised is all converted into carbon dioxide. But the temperature rises, 
and there is a production of carbonic oxide, a gas which, according to Sir I. Lowthian 
Bell, has a greater stability in presence of iron at elevated temperatures. At this 
period the lines of the alkali metals are seen. The gases of the converter, under 
such conditions as exist during the “ boil,” are those of a reducing atmosphere. 
Oxidation of combined carbon to carbonic oxide then continues until near the close of 
the “ fining stage,” and it wifi be noticed that oxidation proceeds with increased 
activity. If we consider that the temperature of the metal at the commencement 
of the “ blow ” is no higher than that of the melting point of cast iron, that free oxygen 
passes through it and carbon dioxide is evolved, there can be no doubt that the 
temperature is insufficient to volatilise manganese if it be present, and, therefo]-e, no 
spectrum of this element is visible. 
When manganese cannot be vaj^orised, iron certainly cannot. Even the alkali 
metals are not carried out of the converter for some five or six minutes. When the 
gases are largely composed of carbonic oxide, and a higher temperature prevails, the 
alkali metals are volatilised, and the principal lines of sodium and potassium are 
observed during different periods up till the termination of the “ blow.” Why the 
red and violet lines of potassium are not visible is, no doubt, owing to the overpower¬ 
ing brilliancy of the other portions of the spectrum, and not because they are absent. 
The best evidence of this is, that on plates specially sensitised, the red line appears, 
and in every case the violet lines have been photographed. 
The curves reduced from Kupelwieser’s analyses are very different in detail, 
tliough the same in general effect. 
