Sulfuric acid exposure limits

Pan and cascade burners are generally more limited ia flexibiHty and are useful only where low sulfur dioxide concentrations are desired. Gases from sulfur burners also contain small amounts of sulfur trioxide, hence the moisture content of the air used can be important ia achieving a corrosion-free operation. Continuous operation at temperatures above the condensation poiat of the product gases is advisable where exposure to steel (qv) surfaces is iavolved. Pressure atomiziag-spray burners, which are particularly suitable when high capacities are needed, are offered by the designers of sulfuric acid plants. 

Health, Safety, and Environmental Factors. Sulfur dioxide has only a moderate acute toxicity (183). The lowest pubHshed human lethal concentration is 1000 ppm for 10 months. The lowest pubHshed human toxic concentration by inhalation is 3 ppm for 5 days or 12 ppm for 1 hour. The lowest pubHshed human lethal concentration is 3000 ppm for 5 months. In solution (as sulfurous acid), the lowest pubHshed toxic dose is 500 flg/kg causing gastrointestinal disturbances. Considerable data is available by other modes of exposure and to other species NIOSH standards are a time-weighted average of 2 ppm and a short-term exposure limit of 5 ppm (183). 

Safety. Chlorosulfuric acid is a strong acid and the principal ha2ard is severe chemical bums when the acid comes into contact with body tissue. The vapor is also ha2ardous and extremely irritating to the skin, eyes, nose, and respiratory tract. Exposure limits for chlorosulfuric acid have not been estabhshed by OSHA or ACGIH. However, chlorosulfuric acid fumes react readily with moisture in the air to form hydrochloric and sulfuric acid mists, which do have estabhshed limits. The OSHA 8-h TWA limits and ACGIH TLV—TWA limits are sulfuric acid = 1 mg/m hydrochloric acid = 5 ppm or 7 mg/m (ceiling limit). 

The following exposure limits have been developed for sulfuric acid. 

OSHA ozone exposure limits, 17 815 OSHA Permissible Exposure Level (PEL), for sulfuric acid, 23 795 OSHA regulations, for vinyl chloride, 25 650, 651... 

The corrosive effects of sulfuric acid on teeth with chronic exposure are well established." The damage, etching of dental enamel followed by erosion of enamel and dentine with loss of tooth substance, is limited to tbe parts of the teeth that are exposed to direct impingement of acid mist upon the surface. Although etching typically occurs after years of occupational exposure, in one case exposure to an average of 0.23mg/m for 4 months was sufficient to initiate erosion. ... 

The experience of Asarco was limited to exposures in different concentrations of sulfuric acid. Researchers studying sulfur concrete indicate that it is resistant to many organic and inorganic compounds, but not to aromatics, strong caustic... 

For quantitative studies in radiation chemistry, it is essential that the energy input into the irradiated volume should be accurately determined. For this purpose, the most versatile and reliable method is the ferrous sulfate dosimeter, proposed by Fricke and Morse. The method involves the use of an air-saturated solution of 10 M ferrous sulfate and 10 M sodium chloride in 0.8 N sulfuric acid. On exposure of the solution to ionizing radiations, the ferrous ion is oxidized to ferric ion, which may conveniently be determined accurately by spectrophotometry. The amount of chemical change is proportional to the total energy-input, independent of dose rate, and (within wide limits) independent of the concentration of ferrous ion, ferric ion, and oxygen. The main reactions involved are as follows. 

In the UK, the long-term exposure limit (8-hour TWA) for sulfuric acid is 1 mg/m. ... 

The Occupational Safety and Health Administration permissible exposure limits for various corrosives are as follows glacial acetic acid, 10 ppm acetic anhydride, 5 ppm hydrofluoric acid, 3 ppm sulfuric acid, lmgm oxalic acid, lmgm nitric acid, 2 ppm bromine, 0.1 ppm chlorine, Ippm fluorine, 1 ppm hydrochloric acid, 5 ppm. 

In the conjunctiva and cornea, sulfur mustard exposure causes loosening of epithelial cells accompanied by corneal edema and opacification (Warthin Weller, 1919). Even low-dose exposure of sulfur mustard to the eyes can be incapacitating (ocular ICt5o = 50 to 100 mg-min/m3). Only limited studies of sulfur mustard-induced eye injuries in animals are available (Kadar et al., 1996 Maumenee Scholz, 1948 Warthin Weller, 1919). These suggest that the microscopic pathology is similar to most chemical injuries with the exception of acid and alkali bums. 

The chemical composition of the different catalysts investigated are collected in Table 1. Also the sulfur contents calculated for complete conversion to Zr(S04)2 are indicated. The experimental sulfur contents are lower than the calculated values. The reaction of the silica-supported zirconia with gaseous sulfur trioxide is therefore not complete and the reaction of zirconium hydroxide and zirconia with sulfuric acid involves only a limited fraction of the zirconia. As to be expected, the specific surface area of the catalyst prepared from zirconium hydroxide is much larger than that of the other catalysts. The catalyst based on calcined zirconia exhibited the X-ray diffraction pattern of zirconia and the catalyst based on zirconium hydroxide showed broadened reflection of zirconia. The bulk water-free zirconium sulfate did not display an X-ray diffraction pattern after exposure to ambient air (relative humidity 50 to 60%) for two weeks the sharp X-ray diffraction pattern of Zr(S04)2-4H20 appeared [1]. 

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