Distribution of inorganic impurities in graphite electrodes was investigated by means of radiography, ash pattern technique, and sulfur print technique. Patterns in the radiographs of the electrodes were found to correspond closely with their ash patterns. In 14″ Acheson electrode, a small quantity of inorganic impurities was found in a relatively uniform distribution, while in 18″ and 30″ Acheson electrodes, an appreciable amount of inorganic impurities was found to intermingle with fine coke powder or coke derived from binder pitch in interstices between coke particles.
Inorganic impurities of 18″ and 30″ electrodes existed in a fiber-like texture and were mainly composed of iron compounds. The fiber-like texture of the impurities suggested that the impurities might have condensed from the vapour phase.
The radiography of graphite electrodes was also proved to be useful in revealing the texture of the electrodes such as shape and distribution of both coke particles and pores.