A statement of the amount made per kilowatt hour may be misleading, since a certain amount of loss is of necessity entailed during this process.
For instance, in practical working it has been found that a furnace return of oï¿½ 504 lb per kilowatt hour is brought down to 0.406 lb per kilowatt hour when the material has been broken up, sorted and packed in air-tight drums. In the tapping process a fixed crucible is used, lined with carbon, the electrode is nearly as big as the crucible and a much higher current density is used.
A 10-12% solution of sodium chloride is caused to flow upwards through the apparatus and to overflow into troughs, by which it is conveyed (if necessary through a cooling apparatus) back to the circulating pump. Such a plant has been reported as giving 0.229 gallon of a liquor containing I% of available chlorine per kilowatt hour, or 0.171 gallon per e.h.p. hour.