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Since the investigation of the health hazards in chromium plating by Bloomfield and Blum (1) in 1928, chromium plating has been widely used in industry where a brilliant luster and a hard corrosionresisting surface are desired. In almost every case a cross-draft ventilation system has been utilized to remove the mists and fumes, but few data regarding the effectiveness of this type of exhaust are available. By measuring the air velocity and sampling the air in a chromium plating shop, an attempt has been made here to evaluate the control with reference to the standards recommended in 1928 (1). Three instruments were used to measure the velocity at the face of the exhaust hood. The kata thermometer and anemometer were used to check the newer and more convenient Alnor velometer. An additional check was obtained by measuring the static suction on the hood. Air samples were collected by the modified Greenburg-Smith impinger (2) at the rate of 1 cubic foot per minute. A 5 percent solution of sodium carbonate (Na2CO3) was used as a collecting medium. Where low concentrations were encountered, samples were taken for several hours, while much shorter sampling periods sufficed for heavy concentrations such as were encountered when no local exhaust was used. In every case the impinger flask was attached directly over the edge of the tank so that the air intake was about 1 foot above the side of the tank and 1 Y2 feet above the solution in the plating tank. When a man is working over the plating tank he breathes air from about this level and should be subjected to the concentrations obtained by this sampling technique. Two samples were collected simultaneously, the suction being produced by two Hancock air ejectors operated by compressed air at 50 to 60 pounds per square inch. The flow was regulated by orifices calibrated to give 1 cubic foot per minute. The amount of chromic acid in these samples was determined by the iodometric method (1). The samples were acidified with sulphuric acid, potassium iodide was added, and then the samples were titrated with 0.01 N sodium thiosulphate, using starch as an indicator. Table 1 summarizes the results obtained. All tests were made using current densities of 150 to 200 amperes per square foot of surface area. Although adequate control was maintained when velocities of about 1,500 and 2,000 feet per minute were created at the face of the |
