OLEUM 20% free

Percent h2so4 °Be Percent Oleum (% Free SO ) Specific Gravity Uses... 

Oleum, % free SO3 % Equivalent H2SO4 Specific gravity (37.78) Freezing point (°C)... 

Oleum is marketed in all strengths up to ca. 70 per cent. SO3. From 0 to 40 per cent, free SO3, it is a liquid from 40 to 60 per cent, free SO3, it is a solid from 60 to 70 per cent, free SO3, it is liquid above 70 per cent, free SO3, it is a solid. The acid must be kept in ground glass stoppered, thick-walled bottles. If it is required to melt the acid, the stopper is removed, a watch glass placed on the mouth of the bottle, and the bottle placed in a layer of sand in an air bath which is warmed with a small flame. The bottle is fitted with a wash bottle attachment, and any desired quantity of acid is forced out by gentle air pressure from a hand or foot bellows (the mouth must not be used) this procedure is far more satisfactory than that of pouring the liquid acid from the bottle. 

In a 500 ml. bolt-head flask, provided with a mechanical stirrer, place 70 ml. of oleum (20 per cent. SO3) and heat it in an oil bath to 70°. By means of a separatory funnel, supported so that the stem is just above the surface of the acid, introduce 41 g. (34 ml.) of nitrobenzene slowly and at such a rate that the temperature of the well-stirred mixture does not rise above 100-105°. When all the nitrobenzene has been introduced, continue the heating at 110-115° for 30 minutes. Remove a test portion and add it to the excess of water. If the odour of nitrobenzene is still apparent, add a further 10 ml. of fuming sulphuric acid, and heat at 110-115° for 15 minutes the reaction mixture should then be free from nitrobenzene. Allow the mixture to cool and pour it with good mechanical stirring on to 200 g. of finely-crushed ice contained in a beaker. AU the nitrobenzenesulphonic acid passes into solution if a little sulphone is present, remove this by filtration. Stir the solution mechanically and add 70 g. of sodium chloride in small portions the sodium salt of m-nitro-benzenesulphonic acid separates as a pasty mass. Continue the stirring for about 30 minutes, allow to stand overnight, filter and press the cake well. The latter will retain sufficient acid to render unnecessary the addition of acid in the subsequent reduction with iron. Spread upon filter paper to dry partially. 

Note. Oleum with 0-30 per cent, free SO, is liquid at 15°. ... 

Oleum. Oleum strengths are usually reported as wt % free SO or percent equivalent sulfuric acid. The formula for converting percent oleum to equivalent sulfuric acid is as follows ... 

Plants producing oleum or Hquid SO typically have one or two additional packed towers irrigated with oleum ahead of the normal SO absorption towers. Partial absorption of SO occurs in these towers, and sulfuric acid is added to maintain desired oleum concentrations. Normally, oleum up to about 35 wt % free SO content can be made in a single tower two towers are used for 40 wt % SO. Liquid SO is produced by heating oleum in a boder to generate SO gas, which is then condensed. Oleums containing SO >40 wt % are usually produced by mixing SO with low concentration oleum. 

Oxidi2ing contaminants, eg, nitric acid and ferric ions, may significantly alter the performance of alloys in sulfuric acid. For example, HasteUoy B-2 performs extremely well in concentrated sulfuric acid but corrodes rapidly in the presence of ferric ions, nitric acid, or free SO iu sulfuric acid. For this reason, HasteUoy B-2 is not recommended for oleum service. 

OB to C02 —85.04%, needles from glac AcOH, mp 262—63° (decomp). Sol in glac AcOH, acet, dioxane py si sol in benz, toluene, xylene amyl ale. Prepn from l-nitro-2-. me thy lnaphthalene by nitration using mixed acids of nitric (d 1.52g/cc), sulfuric (d 1.84 g/cc) oleum (20—25% SO5 free), and heating for one hour at 80° on a water bath. Two other isomers which do not decompose are prepd simultaneously viz, mp (I) 230° ... 

The active paste has a typical composition of 40-50% AM (active matter), 5-9% sodium sulfate, and <1% unsulfonated organic material (free oil). Pastes from oleum sulfonation do not require bleaching. 

As can be seen, water is set free by the reaction. The presence of water retards the sulfonation reaction or prevents it altogether. This is why a very large excess of H2S04 is used to bring the reaction to completion. (The oleum excess is used for the same reason.)... 

The mechanistic details of sulphonation have been less closely explored than those of nitration or halogenation. Benzene itself is sulphonated fairly slowly by hot concentrated sulphuric acid, but rapidly by oleum (the rate then being related to its S03 content) or by S03 in inert solvents. The nature of the actual electrophile depends on the conditions, but is probably always S03 either free or linked to a carrier , e.g. H2S04S03 (H2S207) in sulphuric acid. A small concentration of S03 is developed in H2S04 itself through the equilibrium ... 

Most of the problems of side reactions can be circumvented by using a mixture of unhydrous sulfuric acid (containing no free SO3, a powerful oxidant) and orthoboric acid [4,8], The superacidic nature of this sulfonation mixture ensures complete protonation and the lack of free SO3 excludes the possibility of oxidation. In addition, the number and position of the sulfonate groups can be more effectively controlled than by using oleum for... 

At atmospheric pressure, sulfuric acid has a maximum boiling azeotrope at approximately 98.48% (78,79). At 25°C, the minimum vapor pressure occurs at 99.4% (78). Data and a discussion on the azeotropic composition of sulfuric acid as a function of pressure can also be found in these two references. The vapor pressure exerted by sulfuric acid solutions below the azeotrope is primarily from water vapor above the azeotropic concentration S03 is the primary component of the vapor phase. The vapor of sulfuric acid solutions between 85% H2S04 and 35% free S03 is a mixture of sulfuric acid, water, and sulfur trioxide vapors. At the boiling point, sulfuric acid solutions containing <85% H2S04 evaporate water exclusively those containing >35% free S03 (oleum) evaporate exclusively sulfur trioxide. 

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