The salt solution is prepared in wooden tanks from coarse clean salt (ground rock salt is unsuitable), containing as little iron as possible, in the proportion of 50 pounds to 100 gallons of water. After passing through a gravel or other suitable filter the brine solution is carried by brass pipes to the electrolyser. The rate of flow is adjusted to the temperature of the hypochlorite solution leaving the cell but under normal conditions it is stated that the cell described will pass 40 gallons per hour with a consumption of 70 amperes and produce 2-1/2 pounds of chlorine per hour. This is equal to 8 pounds of salt and 3.08 kilowatt hours per pound of chlorine. After the cells have been operated for several months the efficiency usually falls and 10-11 pounds of salt and 3.5-3.7 kilowatt hours are required for the production of one pound of chlorine. The concentration of the hypochlorite solution is usually about 6 grams per litre. Rickard[3] stated that by cooling the Dayton cell with ice 1 pound of chlorine could be produced from 2.65 kilowatt hours and 6.9 pounds of sodium chloride; without cooling the figures were 3.62 kilowatt hours and 7.2 pounds of salt. Based on the figures that have been obtained from mature cells, the efficiency of the Dayton cell as compared with those described by Kershaw is as follows: ------------------+----------------------+---------------------- | SALT. | POWER. | PER POUND OF AVAILABLE CHLORINE. Type of Cell. +----------+-----------+----------+----------- | Pounds. | Per Cent | Kilowatt | Efficiency | | Consumed. | Hours. | Per Cent. ------------------+----------+-----------+----------+----------- Haas and Oettel | 10.7 | 15.4 | 3.8 | 31.9 Kellner | 7.5 | 22.0 | 2.75 | 43.9 Hermite | 11.2 | 14.5 | 2.87 | 42.2 Mather and Platt | .... | .... | 2.75 | 43.9 Dayton | 10.0 | 16.5 | 3.6 | 33.6 Theoretical | 1.65 | 100.0 | 1.21 | 100.0 ------------------+----------+-----------+----------+----------- The cost of production depends upon local conditions: if alternating current is available at $30 per horse-power per annum, and low-grade salt can be obtained for $5 per ton the cost of 1 pound of chlorine would be -----------------+---------------------------- | COST (CENTS) PER POUND OF | AVAILABLE CHLORINE. Type of Cell. +--------+----------+-------- | Salt. | Current. | Total. -----------------+--------+----------+-------- Haas and Oettel | 2.67 | 1.97 | 4.64 Kellner | 1.87 | 1.43 | 3.30 Hermite | 2.80 | 1.49 | 4.29 Dayton | 2.50 | 1.92 | 4.42 -----------------+--------+----------+--------