IT is well known that when the heat is sufficient, carbonic oxide
reduces the oxide of iron to metal with the production of carbon dioxide
(carbonic acid). On the other hand, at lower temperatures carbon dioxide
oxidizes metallic iron, forming carbonic oxide. J. Lowthian Bell's
celebrated researches (see SCIENTIFIC AMERICAN, p. 199, March 31, 1883)
established the point of equilibrium where in the presence of both
monoxide and dioxide the reducing action of the one just counterbalances
the oxidizing action of the other.
At the suggestion of Prof. R. Akermann, of Stockholm, C.G. Särnstrom has
conducted a similar series of forty-five experiments, the expense being
borne by the Jernkontor. About 1 gramme of oxide of iron was placed in a
porcelain boat, and slid in a porcelain tube 18 millimeters (¾ inch) in
diameter and 635 millimeters long (25 inches). This was exposed to the
action of a current of mixed carbon dioxide and monoxide made by heating
oxalic acid and concentrated sulphuric acid. It was mixed with carbon
dioxide as required, then analyzed, and preserved in gasometers holding
66 liters. Before using, it is passed over phosphorus and chloride of
calcium, and through sulphuric acid. The porcelain tube and boat were
heated to from 300° to 600° C. (572° to 1,652° Fahr.) while the gases
were passing, and then the state of oxidation determined. It was found
that the larger the quantity of dioxide the higher the degree of
oxidation, and the larger the proportion of monoxide the lower the
degree of oxidation.
The details of the experiment indicate that a saving of fuel in the
blast furnace could best be accomplished by the use of a very hot blast,
introducing some carbon monoxide into the blast, provided, of course,
that this gas can be made outside of the blast furnace more cheaply than
inside of it. Nevertheless, 643 lb. of carbon must be burned to
every 1,000 lb. of iron reduced, if carbonic oxide is exclusively
employed.--_Stahl und Eisen_.
* * * * *