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892 CHAPTER 42 1950 Guide vided, and . a shower head or its equivalent provided at or very near the point where the chemicals are mixed. Chemicals should always be washed from the skin with large volumes of water. For the handling of chlorine and chlorinators, the U. S. Public Health Service19 stipulates the following.safety requirements: 1. Suitable gas masks and a Bmall bottle Of ammonia for testing for leaks should be kept at convenient points immediately outside the room or enclosure in which chlo rine is being stored or is in use. Gas masks should be inspected at regular intervals and kept in serviceable condition. Note:--All-purpose masks offer adequate pro tection only when the concentration of acid gases does not exceed two per cent-- See safe Practises Pamphlet #64 National Safety Council. 2. Chlorinating equipment and cylinders of chlorine should be housed preferably in separate buildings above the ground level. 3. The room. or building housing chlorinators in service should be maintained at a temperature above 60 F, but never in excess of the normal summer temperature. The cylinders of chlorine should be shielded, where necessary, from excessive heat or cold. Direct heat should not be applied to cylinders of chlorine, nor should hot water be poured over them or come in contact with the cylinder valve. 4. Adequate ventilation should be provided for all enclosures in which chlorine is being fed or stored. 5. All joints of tubing connecting chlorine cylinder and chlorinators should be kept absolutely tight and inspected frequently to insure tightness. Tubing should slope upward from thq cylinder. LEGAL REGULATIONS In a number of states, the water used for humidification, even in in dustrial plants, is required to meet drinking-water standards insofar as bacteriological quality is concerned. A ruling of the U. S. Department of Agriculture, Meat Inspection Division prohibits the use of chromate. in water used for air washing when the air later contacts foodstuffs.40 There is an ever growing consciousness on the part- of public health officials of:the necessity: for regulations to protect potable water supplies. Attesting this is an ordinance41 now in effect in Detroit, Michigan, which stipulates in part: . "No physical connection shall be maintained between lines carrying city water and pipes, pumps, or tanks supplied from any other source. Where dual supplies are necessary or desired, lines carrying city water must be protected against back flow of polluted water by an atmospheric gap. Secondary supplies and emergency sources shall include: surface waters from rivers, lakes, ponds, lagoons, and reservoirs; well waters both deep and shallow; any supply of water which has been stored, held, or reserved after being .used for industrial purposes; cooling water,, or water which has in any way been treated, processed, or has been subjected or exposed to any con tamination of a bacteriological or chemical nature; and water from any other source than the city supply:" ~ ............ .'.'The'IT. S'. Public Health.Service.stipulates: "Salts of barium, hexavalent chromium, heavy metal glucosides, or other sub stances with deleterious physiological effects, shall not be allowed in the water supply.system:" - The same agency recommends that the concentration of the substances listed be held below the values; cited in Table 8. The Board of Directors of the American Water Works Association has accepted these values as standard for all public water supplies in the United States.41 While their action is not binding, prudence dictates that no form of treatment should be used that will result in raising the concentration of the substances listed above the value cited. " Since virtually all of the permissible chemicals used for scale, slime, and corrosion control have deleterious, physiological -effects if taken internally \ .Corrosion and Water Formed Deposits, Causes and Prevention 893 1 Table Recommended Maximum Allowable Content in Water Supply ,, Sijbsuxcx : Max Concentration, ' ppm Substance , Max Concentration, PPm Copper........... ...................... Iron <feManganese (Total).. Magnesium........................... Zinc....................................... Lead...................................... Fluorine................. ........... %U.S PuMte HtaUh Service. 3.0 0.3 125.0 15.0 0.1 1.0 Arsenic.................................. Selenium.'........... ................. Phenols (Total).:................ Poly-phosphate of Sodium.. pH Value @ 25C................ 0.05 0.05 0.001 10.0 10.6 in relatively large doses, they should always be carefully proportioned. To insure this, the Detroit ordinance stipulates that the chemical feeding device must have the following major characteristics: "1. There shall be a visible means of checking the quantity of material being applied by the feeding device. - -- 2. A water metering device, sealed to prevent- tampering, shall be installed to measure the flow of water being treated. 3. The device shall be constructed so that in the event of back-flow or vacuums, the maximum amount of material that may be possibly back-siphoned from the device or any of its attachments or parts shall not exceed one fluid ounce. 4. Should there be a failure of the water metering device or the water supply, the feeding device shall automatically cease operating." REFERENCES * Annual Report (1947) Committee D-19 (American Society for Testing Materials). ' * Corrosion Handbook, edited by H. H. Uhlig, (John Wiley & Sons, p. 27). 1 Discussion, Corrosion and Material Protection, May 1945, p. 2. '4 Round-Table Discussion on Organizing the Classification of Industrial Waters, by W. C. Schroeder (Proceedings, American Society for Testing Materials, Vol. 44 1944, p. 1051) . 4 Typical Water Analyses tor Classification with Reference to Industrial Use, by W. D. Collins (Proceedings, American Society for Testing Materials, Vol. 44, 1944, p; 1057). 4 A.S.T.M. Standard D-596--41 (American Society for Testing Materials). I Discussion on Preventing Solution of CO, in Condensates, by E. W. Guernsey (A.S.H.V.E. Transactions, Vol. 51,1945, p. 69). 4 Studies of the Mechanism of Solution of CO, in Condensates Formed in Steam Heating Systems of Buildings, by L. F. Collins (A.S.H.V.E. Transactions, Vol. 51, 1945, p. 39). : 4 The Analytical Control of Anti-Corrosion Water Treatment, by W.-F. Langelier (Journal, American Water works Association, Vol. 28, 1936, p. 1500). 10 Surface-Active Properties of Hexametaphosphate, by G. B. Hatch and Owen Rice (Industrial and Engineering Chemistry, Vol. 31,1939, p. 51). u Slime Control in Cooling Equipment with Phenol Derivatives, by J. A. Holmes (Proceedings, Annual Water Conference, Engineers Society of Western Pennsylvania, 1944,p. 61). II Tuberculation of Mains as Affected by Bacteria, by H. G. Reddick and S. E. Linderman (Journal, New England Water Works Association, Vol. 46, 1932, No. 42). 14 Microbiological Anerobic Corrosion of Steel Pipe Lines, by R. F. Hadley (The Oil and Gas Journal, September, 1939). 14 Tests of Corrosion Inhibitors for Water Treatment in Air Conditioning Equip-