INDUSTRIAL
ENGINEERING CHEMISTRY
AND
ANALYTICAL E D I T I O N PUBLISHED
BY
THE
AMERICAN
CHEMICAL
SOCIETY
0
HARRISON
E.
HOWE,
EDITOR
Rapid Determination of Oxygen in Steel L. SISGER, The Naval Research Laboratory, ;inacostia, D. C.
A
mixtures of tin and antimony to effect fusion of the steel a t a lower temperature. I n the work described here, tin was used as the fluxing agent. -4mixture of tin and antimony in equal parts by weight was also tried b u t found objectionable, as the antimony vaporizes too readily a t the temperature employed.
COSSIDERABLE amount of work has been done on the influence of oxygen upon the properties of steel, but i t has been hindered by the lack of a simple, rapid method for the quantitative estimation of oxygen. Several methods (3) have been used for the determination of oxygen in steel and some give good results in the hands of careful, experienced analysts. However, all the methods that have been used are too slow for practical use and most of them require considerable care in manipulation. It is t h e purpose of this paper to show the results obtained in the determination of oxygen in steel by a nitrogen fusion method. This is so called because of its similarity to the vacuum fusion method, in that the reduction of the oxides is obtained by graphite. I n the \%tuum fusion method, reduction takes place in a vacuum a t a temperature of about 1600" to 1650' C.; whereas in the nitrogen fusion method, described below, reduction takes place in an atmosphere of nitrogen a t a temperature of 1200" to 1250" C. I n both methods the oxygen in the metal (present as oxide in solution or oxide inclusions) is converted to carbon monoxide. This gas may be analyzed either volumetrically or gravimetrically. I n the gravimetric method the gas is passed over hot copper oxide for conversion of carbon monoxide to carbon dioxide, which is then absorbed in a weighed Ascarite tube. A complete description of the vacuum fusion method has been given by T'acher and Jordan ( 4 ) To olniate the use of the high temDerat u r e employed i n - t h e GA5 v a c u u m f u s i o n method, various experimenters have used tin or antimony or
Purification of Sitrogen The steel sample was melted in an atmosphere of pure nitrogen. This gas was prepared by first analyzing a cylinder of nitrogen for its oxygen content and then blowing in hydrogen in quantity slightly greater than equivalent to the oxygen found present. An analysis of a cylinder of gas prepared as ahore showed 0.67 per cent by volume of oxygen and 1.51 per cent by volume of hydrogen. Both gases were subsequently removed by passing first over palladinized pumice (at 400" to 500" C.) to remove oxygen and then over copper oxide (at 300" C.) to remove the excess hydrogen. The water formed was then taken out by suitable absorbents. A ready supply of pure nitrogen was thus always available during the course of an analysis.
Description of Apparatus The train used is shown in Figure 1. Gas from the nitrogen cylinder by-passes the mercury safety bottle, A . B is a 2-way
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A
C
FIGURE1. SCHEMATIC D I A GRAM OF OXYGEN DETERMINATIOS
D. E.
[IQ
ASSEMBLY
Ascarite tower Palladiniaed pumice tower (400-500° C.)
G, P. C o p p e r o x i d e t o w e r s mono c H. Sui?
