Determination of gases in metals and alloys by vacuum technique

Oxygen, hydrogen and nitrogen are the three main gaseous elements, which adversely affect the physical and mechanical properties of metals and alloys when present in them. The accurate determination of these gases, generally contained in very low amounts, was really a difficult problem, till the introduction of the vacuum technique, which has now been accepted as a standard method for the simultaneous determination of oxygen, nitrogen and hydrogen. The Vacuum Fusion Method basically consists in melting the sample in a graphite crucible under high vacuum to effect reduction of oxides in presence of excess dissolved carbon forming CO, which is then pumped, together with H2 and N2, into a gas analysis apparatus for final analysis of the gas. In addition to steel, titanium, molybdenum, chromium, high temperature alloys, copper and silver have been analysed for their gaseous content using the iron bath technique. However iron and steel make an ideal liquid metal bath containing excess dissolved carbon to perpetuate the reactions with the oxides of the metals. (Mr. N.G. Banerjee, Junior Scientific Officer, National Metallurgical Laboratory, Jamshedpur)