Fig. 11.—Sections of Allen-Moore Cell.
Each cell has a capacity of 32 pounds of chlorine per day and the gas flow is determined by measuring the volume of caustic soda produced in a given period of time and calculating the weight from the volume and concentration as determined by titration with standard acid; each gram of NaOH is equal to 0.88 gram of chlorine. The efficiency of the cell is obtained by dividing the number of grams of chlorine produced per hour by the product of the current volume (in amperes) and the factor 1.33, the theoretical production of chlorine for one ampere hour. The average efficiency of the Montreal cells was found to be 93 per cent. The installation comprises four cells, one being held in reserve, and the annual cost of producing 90 pounds of chlorine per day is given as $2,500. The details are:
| Salt at $8.00 per ton, delivered | $500.00 |
| Power, 15 H.P., at $30.00 flat rate | 450.00 |
| Labour and superintendence | 500.00 |
| Interest at 6 per cent on capital cost | 300.00 |
| Depreciation, 15 per cent | 750.00 |
| ———— | |
| $2,500.00 |
cost per pound of chlorine = 7.6 cents.
The diaphragm cells, like the non-diaphragm ones, operate most efficiently under a constant load; they are consequently suitable for treating the effluent of filter plants.
Where very cheap electrical power can be obtained, the cost per pound of available chlorine is less for the electrolytic method just described than for liquid chlorine or chlorine obtained from bleach; but this condition obtains in very few places. Mr. J. A. Meadows has suggested to the author that the cost could be reduced by converting the chlorine gas into hypochlorite and then adding dilute ammonia as in the chloramine process (vide [page 115]). The caustic liquor, usually run to waste from the cathodic compartment, could be delivered into a feed box from which it would be drawn off by the water injector used for dissolving the chlorine gas.
BIBLIOGRAPHY
[1] Lunge and Landolt. Jour. Soc. Dyers and Colourists, Nov. 25, 1885.