1060
INDUSTRIAL AND ENGINEERING CHEMISTRY
ated by chemical methods as by manganese dioxide and acid and salt and from gas liquefied in cylinders. It has been applied to sewage directly as a gas and as an aqueous solution. Chlorine has also been applied experimentally as magnesium hypochlorite, as hypochlorous acid, and in combination with ammonium compounds such as nitrogen trichloride and as chloramine. Of these methods the most promising for future use is compressed chlorine from cylinders for large requirements and sodium hypochlorite where small amounts of chlorine are required and where the presence of compressed chlorine is undesirable. Chlorine can be applied to sewage at any place in which it can be contacted with the sewage from its raw state to any stage in the process of purification except in the chambers where biological action is going on. If used a t this stage it would stop the biological action and interfere with the disposal method. However, the chlorine is almost invariably applied to the effluent from the process because less chlorine is required. I n case chlorine is applied directly to raw sewage it is always desirable to screen the sewage and remove the large particles which are difficult to penetrate and sterilize. If possible, sewage should not be allowed to become septic before treatment, as this indreases the amount of chlorine required. Domestic sewage requires usually somewhere between 3 and 20 parts per million, depending upon its concentration and condition. Usually domestic sewage can be satisfactorily treated with from 5 to 10 parts per million of chlorine to give a 95 to 99 per cent reduction in bacterial count. Applications
There are reasons for the chlorination of sewage other than to protect public health. Tannery wastes are chlorinated to protect cattle from anthrax. Large amounts of chlorine are necessary, 250 parts per million being required to kill the spore-forming anthrax in the presence of the large amounts of organic materials in tannery waste. Chlorine is being used to protect bathing beaches. The Surgeon General of the U. S. Army says that “bathing pool water is, to all intents and purposes, drinking water and must, in general, conform, with the same sanitary standards.” Many swimming pools are now being chlorinated to protect public health. Most of the sewage in the city of Cleveland during the bathing season is treated with chlorine to protect the bathing beaches of the lake. These installations of equipment are the largest in the world for the handling of chlorine for sterilization pnposes. I n the Tidal Basin a t Washington, D. C., a chlorinator was mounted in a boat and the chlorine distributed through the basin as the boat traveled around. Very fine results were obtained from the use of this method. Protection of food supplies by chlorination of sewage is a growing and promising use of chlorine. The oyster industry is already widely protected by the treatment of sewage which may contaminate oyster beds. A further protection of the oyster supply by the use of chlorine is now being contemplated. Two methods are proposed: first, to treat the shelled oysters with sufficient chlorine water to sterilize the containing liquid; and, second, to immerse the unshelled oyster in strong chlorine water, which exhausts itself by reaction on the organic material on the outside of the shells and renders everything outside of the oyster sterile. As soon as the chlorine has been absorbed the oyster opens the shell and starts to circulate water through his respiration system. The circulation of sterile water by the oyster will, it is claimed, in the course of 6 hours completely eliminate any contaminating organisms within the oyster. By giving‘two successive treatments oysters can be rendered satisfactory for use as food. Probably both of these methods of oyster treatment
Vol. 17, No. 10
should be used to remove contamination within the oyster and to safeguard against contamination of the oysters during or after shelling. A further use of chlorine in connection with food supplies is possible, though not practiced. Probably the greatest waste of a natural resource in our present civilization is the loss of human wastes as fertilizer. I n certain regions of this country it should be possible for the sewage effluent from the cities to be returned to the land, and this effluent should be first rendered sterile by chlorination. Perhaps this generation will see this process in use. Chlorine can also be used for the decolorization of industrial wastes so that these wastes can be discharged into streams without damaging the stream. This has been practiced for some time in isolated cases and is now coming into extended use in paper mills, textile and dye houses, and many other industrial plants who must discharge satisfactory waste liquors or remove their plants from the present location. I n those centers of population where the water receiving the sewage is overloaded and becoming septic produces objectionable odors, it is feasible to chlorinate the sewage discharging into such streams sufficiently to retard the biological action in the streams and permit the sewage to be swept out further into the larger bodies of water. This seems to be a feasible solution of the problem that will eventually develop in the Hudson River a t New York City. It would be difficult to install modern sewage treatment plants in New York. If the sewage were chlorinated sufficiently to retard the biological action of the river, the capacity of the stream for handling sewage would be increased and the time delayed when increasing concentration of population would make the Hudson and East Rivers septic and damaging to the city’s interests. Chlorine is now being extensively used to deodorize the obnoxious gases being discharged from stacks, particularly those from garbage and fish reduction plants and packing houses. This use is only in its infancy. Theory of Action of Chlorine
The manner in which chlorine acts in sterilizing water and sewage is of interest. The‘evidence is strongly in favor of the theory that the killing action is not due to direct oxidation by the chlorine but to the formation of some substance toxic to the organism. Substances of greater oxidizing potential than chlorine, such as permanganate or peroxide, need to be used in much greater equivalent amount than does chlorine to show similar sterilizing action. The oxidizing power of chlorine itself can be considerably reduced by combination with ammonium to form either nitrogen trichloride or chloramine, without any loss in its sterilizing capacity and very little alteration of its sterilizing rate, though the compounds, particularly chloramine, have a relatively low oxidizing potential. Chlorine probably acts by attacking the lipoid protein surface of the cellular organisms and forming there some substance which interferes with further cell division, thereby stopping regeneration and resulting in the death of the organisms.
Change in Motor Gasoline Specification A tentative change in the specification for U. S. Government motor gasoline, the principal feature of which is the elimination of the initial and end point requirements, has been voted by the Technical Committee on Lubricants and Liquid Fuels of the Federal Specifications Board. The change, however, will not be immediately effective, as the committee feels that it is necessary first to purchase limited amounts of gasoline on the tentative specification for experimental test. I n voting the tentative change, the committee believed that if the gasoline meets the present distillation requirements a t the 20, 50, and 90 per cent points it should be satisfactory.
