177. There are several forms of generator. That described differs slightly from those in general use. In Deetken's generator, with water joint cover, the wall of the water chamber is not high enough to allow of filling the vessel with water, to expel the chlorine. Kustel describes one in which the stem of the stirrer passes through a stuffing box instead of a water joint, and in place of a water joint for the main cover, is a shallow groove containing clay and a little water. I have used this joint, and it answers very well, but hardly allows of filling the generator with water. A stirrer is not indispensable; at Crosby's works in Nevada City it was not used.

I think the apparatus shown in Plate 5 has some advantages over the others. Generators for chlorine are sometimes made like a "carbonic acid gas" generator, so that any required pressure can be had, but much pressure is not required in the ordinary way of working ores with chlorine.