Abstract: An electrode assembly is described which generally comprises a first electrode, a pair of second planar electrodes, a generally rectangular frame member for supporting each of the second electrodes substantially along three sides thereof, the rectangular frame member having a pair of spaced inwardly extending channels through which said second electrodes slide into and which mask the edges of said second electrodes along the three supported sides, and a laterally displaced integrally formed, inwardly facing elongate channel along an unsupported side of the second electrode which is adjacent to an external face of one of the second electrodes and shaped to receive one side of the first electrode while masking the adjacent second electrode along the unsupported side thereof, a generally elongated frame member coupled to the rectangular frame member between the second electrodes along the unsupported edge thereof, and conduit means associated with the elongated frame member for conveying fluid to the cavity betw