Sulfuric acid is a highly corrosive acid. Concentrated acid can cause severe burn on skin contact. Contact with eyes can damage vision.
Sulfuric acid is manufactured by two processes; namely, the chamber process and the contact process. The chamber process was discovered in 1746 and was used to produce sulfuric acid for over a century. This process was replaced by the contact process which has a lower production cost and yields a more concentrated acid needed for most industrial applications. The chamber process is obsolete now but for historical interest it is outlined below.
In the chamber process, nitric oxide catalyzes the oxidation of sulfur dioxide to trioxide:
The reaction is homogeneously catalyzed by NO. Although the oxidation process is exothermic and spontaneous, the reaction is very slow without a catalyst. The mechanism of the reaction is as follows:
2NO + O2 → 2NO2 (fast)
NO2 + SO2 → NO + SO3 (fast)
Practically all sulfuric acid is now made by the contact process. The starting material is sulfur dioxide, which is made by various methods, such as burning sulfur in dry air:
S (s) + O2( g) → SO2 (g)
or by burning pyrites or hydrogen sulfide:
4FeS2(s) + 11O2(g) → 8SO2 (g) + 2Fe2O3 (s)
2H2S (g) + 3O2 (g) → 2SO2 (g) + 2H2O(g)
Sulfur dioxide produced is reacted with oxygen in the presence of a catalyst to form sulfur trioxide:
2SO2 (g) + O2 (g) → 2SO3 (g)
Sulfur trioxide produced above by the contact process is absorbed in sulfuric acid to form pyrosulfuric acid, H2S2O7, which is diluted with water to form sulfuric acid:
SO3 (g) + H2SO4(l) → H2S2O7 (l)
H2S2O7 (l) + H2O (l) → 2H2SO4(l)
Sulfur trioxide also can be dissolved in water to form sulfuric acid. The dissolution of sulfur trioxide mist, however, is difficult to attain. Most plants employ sulfuric acid to dissolve SO3 vapor which can be diluted to obtain sulfuric acid of desired concentration.
In manufacture of fertilizers, explosives, dyestuffs, other acids, parchment paper, glue, purification of petroleum, pickling of metal.
Special Hazards of Combustion Products: Toxic and irritating vapors are generated.
Reacts violently with water. Strong irritant
viscous liquid, is a mixture of sulfur trioxide dissolved in sulfuric acid. The SO3 content may range between 15 and 30%.
Sulfuric acid probably is the most important industrial chemical of modern time. Most sulfuric acid manufactured is used by the fertilizer industry for making phosphoric acid and phosphate fertilizers.
Sulfuric acid has numerous applications. Some major uses include extracting ores; pickling metal; making explosives; manufacturing dyes, glues, and parchment papers; producing nitric and other acids; purifying petroleum; preparing metal sulfates; and synthesizing many organics. Sulfuric acid also is used in lead storage batteries for automobiles. The lead storage battery was invented by Gaston Plante in 1859. Sulfuric acid is used heavily in sulfonation, estertification, oxidation, dehydration, and acid-base neutralization reactions.
Sulfuric acid is a common laboratory reagent used for laboratory preparation of a large number of salts; as a dehydrating agent; as a component of chromic mixture for cleaning glassware; and in acid-base titration. The acid has been in wide usage in various industrial applications for more than two hundred years. Commercial concentrated acid has an assay of 95 to 98% H2SO4. Its normality is 36 N and density 1.834 to 1.836 g/mL.
Acid mist is irritating to eyes, nose and throat. Liquid causes severe burns of skin and eyes.
SULFURIC ACID reacts as a strong acid, as an oxidizing agent and as a dehydrating agent. Chars wood, sugar and many other organic materials on contact. The heat from these reactions may ignite the wood, sugar or organic matter. May react explosively with acetic acid, acetic anhydride, acetonitrile, acrolein, acrylic acid, acrylonitrile, allyl alcohol, allyl chloride, ammonium hydroxide, aniline, cresol, butyraldehyde, cumene, ethyl acetate, ethylene diamine, ethylene glycol, glyoxal, isoprene, isopropyl alcohol, methyl ethyl ketone, propylene oxide, pyridine, styrene, vinyl acetate; strong bases (sodium hydroxide, potassium hydroxide) or mineral acids (nitric acid, hydrochloric acid, hydrofluoric acid) [Lewis, 3rd ed., 1993, p. 1195]. Mixing in equal molar portions with any of the following substances in a closed container caused the temperature and pressure to increase: 2-aminoethanol, ammonium hydroxide (28%), chlorosulfonic acid, ethylenediamine, ethyleneimine, ethylene cyanohydrin, hydrochloric acid (36%), hydrofluoric acid (48.7%), isopropyl alcohol, nitric acid (70%), 2-nitropropane, propiolactone, propylene oxide, pyridine, styrene monomer, sodium hydroxide, sulfolane, vinyl acetate, vinylidene chloride [NFPA 1991]. Extremely hazardous in contact with carbides, bromates, chlorates, fulminates, picrates, and powdered metals. May induce violent polymerization in polymerizable organic compounds such as allyl chloride. Reacts exothermically with sodium hypochlorite to produce chlorine gas.
Thick fuming yellow liquid. Density 16.5 lb / gal. Very toxic by inhalation. Corrosive to metals and tissue, quickly causing severe burns. Used to make chemicals, dyes, explosives and in petroleum refining.
Air & Water Reactions
Fumes in air. Soluble in water; dissolution generates dangerous amounts of heat that can cause localized boiling and spattering of the acidic mixture and generate heavy fumes. During sulfonation of mononitrobenzene with fuming sulfuric acid, a leak from an internal cooling coil permitted water to enter the reaction tank. A violent eruption occurred due to the heat of solution [MCA Case History 944(1963)].