Document dnexjNd5nmz4GGOVx2O54b1p6

(5 <c=(J 0o C=3 Industrial Hygiene Digest February, 1961 produced if sulfur dioxide is present is compared with a standard stain chart or with a disk of standard tints in order to determine the concentration of the gas. A series of 5 colors, representing 1 to 20 ppm of sulfur dioxide in a 360 ml. sample, was found to be adequate. -- APCA Absta. 183 A Spectrophotometric Method for the Determination of Mercaptans in Air. H. Moore, H. L. Helwig and R. J. Graul. Am. lnd. Hyg. Assn. J. ]_, 466-470 (Dec. 1960). The method described is quick and accurate and determinations may be made usin| apparatus common in air pollution and industrial hygiene work. The method determines tota mercaptans and does not differentiate between individual mercaptans although it is most sen sitive to the low molecular weight alkanethiols. Hydrogen sulfide, sulfur dioxide,, and nitro gen dioxide do not interfere at the concentrations usually encountered in air pollution and in dustrial hygiene studies. -- Authors' conclusions PREVENTIVE ENGINEERING 184 Recommendations on Heights for New Industrial Chimneys. G. Nonhebel. Smokeless Air, No. 1 14, 280-299 (Summer 1960). Engineers responsible for the design of new factories are frequently faced with the difficulty in deciding the height of chimneys to disperse adequately the discharged gases and residual dust. Under the Clean Air Act, local authorities must approve the height of new chimneys. The major consideration is the effect of the discharge at ground level. For mulae have been used for some years for calculating the gas concentration and rate of dust fall under normal weather conditions. From a review of available information, recommenda tions are now made that the height of a new chimney serving a large plant should be such that the calculated 3-minute maximum concentration of sulfur dioxide at ground level should not exceed 40 parts per hundred million in areas of heavy industry or high housing density and 50 pphm in other areas. Similarly, the calculated maximum rate of deposit of grit and dust from a new chimney should not exceed 1000 g./lOO sq, m, per month with a wind direction constant within an octant. The formulae proposed are not applicable to emissions from re latively low chimneys serving small plants; consequently, recommendations based on experi ence are made for a sliding scale of heights from 60 to 120 ft. for boiler plants of aggregate capacity 5000 to 33,000 lb. /hr. Worked examples show that rate of dust deposit rather than ground-level concentration of sulfur dioxide is usually the factor which should control the height of boiler plant chimneys. Prevention of emission of particles or aggregates larger than 76 microns is most important. Additional factors meriting consideration are: (1) rate of ground coverage by a film of deposited dust (less than 0.04% per day suggested); (2) dis tance from the chimney at which dusty plumes become substantially invisible; (3) chimney heights suggested. - Public Health Eng, Abets, 185 Correlation of Dust Scrubber Efficiency. K. T. Semrau. J. Air Pollution Control Assn. 10, 200-207 (June 1960). Data correlated in this and an earlier paper are summarised in a table and figure. In all cases it is found that the number of transfer units may be represented by a simple ex ponential function of the contacting power; Correlation of the literature data generally con firms the findings of the earlier studies, on the relationship of efficiency and contacting powe Efficiency is found to have little relation to scrubber design and geometry, but to be depender on the properties of the aerosol and on the contacting power. There are few data to show the effect of scrubber size, but a number of the studies cited report that there are essentially no 4 '* 23 03120759