Oleum estimation

Sulfuric acid, Sulfur trioxide Vervalin, H. C., Hydrocarbon Process., 1976, 55(9), 323 Dining sulfonation of 4-nitrotoluene at 32° C with 24% oleum in a 2000 1 vessel, a runaway decomposition reaction set in and ejected the contents as a carbonaceous mass. The thermal decomposition temperature was subsequently estimated as 52°C (but see above). 

For solutions containing sulphuric acid only, direct titration with standard alkali, and measurement of the specific gravity, are possible as methods of estimation, provided that the process in either case is, if necessary, preceded by suitable dilution (see p. 165). Thermometric methods have also been suggested, depending on the rise in temperature when the acid is mixed with water, or when titrated with barium chloride solution.4 The water content of the concentrated acid may be determined by similar titration with oleum which has been standardised thermometrically by 80 per cent, sulphuric acid (see p. 147 ).5... 

The results obtained are a little high, as oleum contains a small percentage of S02. This may be estimated by titrating 250 c.cs. with N/10 iodine solution, using starch as indicator. By subtracting this result from the total obtained by titration with NaOH, the true percentage of S03 can be calculated. 

Oleum.—Oleum is supplied in all strengths up to 70% free S03. From 0—40% free S03 it is liquid from 40—60% free S03 it is solid from 60—70% free S03 it is liquid above 70% it is solid. The acid should be kept in well-stoppered, stout glass bottles, and when it is necessary to melt the acid, the stopper is withdrawn, a watch-glass placed on the mouth of the bottle, and the bottle placed on a layer of sand in a large vessel or oil bath which is warmed with a small flame. The bottle is fitted with a wash-bottle attachment, and any desired quantity is forced out by gentle air pressure from hand or foot bellows (the mouth must not be used). For the preparation of oleum of definite strengths, see p. 314. Usual impurities ferric sulphate, sulphur dioxide and lead sulphate. For estimation, see p. 313. 

Under optimum conditions, the reaction time for this process has been calculated at 1.5 hr at 180 C, using a seven-stage reactor and employing 10 moles of benzene per mole of sulfuric acid. In contrast, the same process operated in batches (see pp. 311 and 371) at 160-180°C ould require 14 hr and 6-8 moles of benzene per mole reacted. Thus, the continuous method increases by nearly ten times the capacity of the batch method. It is further estimated that the ratio of benzene used to benzene reacted could be reduced as low as 3 1 by doubling the time of reaction. The efficiency of the process can be further increased by using 10 per cent oleum instead of sulfuric acid, thereby reducing the required water removal without substantially raising by-prosulfone formation. This type of process has been used commercially in the United States. ... 

The Chemical Emergency Preparedness and Prevention Office has estimated the zone of vulnerability under worst-case scenario conditions for facilities containing different hazardous substances. They conclude that for a facility containing toxic substances, the median distance from the facility to the outer edge of its vulnerable zone is 1.6 miles. Flammable substances have a worst-case scenario vulnerability zone whose median distance reaches 0.4 miles from the facility. However, many facilities reported vulnerability zones extending 14 miles from the facility (primarily for urban area releases of chlorine stored in 90-ton rail tank cars) and 25 miles (for rural releases of chlorine stored in 90-ton rail tank cars). Other chemicals for which the reported vulnerability zone equaled or exceeded 25 miles include anhydrous ammonia, hydrogen fluoride, sulfur dioxide, chlorine dioxide, oleum (fuming sulfuric acid). 

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