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Key Chemicals Month
This month we feature chemicals that have important applications in industry and the lab.—Ed.
Sulfuric acid (H2SO4) is the most-produced chemical globally, with an (�333 million US tons). The market size is expected to grow to �364 million tonnes by 2030.
H2SO4 has been known for at least two millennia, typically by the names “vitriol� or “oil of vitriol�. It was widely used by alchemists in medieval times. Its first crude manufacturing process, in the 16th century, consisted of burning sulfur in the presence of water. This method converted barely 1% of the sulfur to H2SO4; most of the sulfur was oxidized to sulfur dioxide (SO2). A century later, this process was improved by adding nitrate salts to the water.
Another improvement came in 1746 with the lead chamber process, which used nitric oxide (NO) to boost the yield and large lead-lined reactors instead of glass vessels to increase production. The reaction sequence was
2NO + O2 � NO2
NO2 + SO2 + H2O � H2SO4 + NO
The most efficient process, and the one used today, was invented in 1831 by Peregrine Phillips, Jr., of Bristol, UK. Called the contact process, it consists of burning sulfur to SO2, which is catalytically oxidized to sulfur trioxide (SO3). The SO3Â is then added to water to produce concentrated H2SO4. The reaction sequence starting from SO2 is
SO2 + O2 � SO3
SO3 + H2O � H2SO4
The original catalyst was platinum, but this was later changed to the less expensive and more durable vanadium pentoxide (V2O5).
Commercial concentrated H2SO4 contains 98 wt% acid; the remainder is water. Pure H2SO4 gives off SO3, making it hazardous to work with. The concentrated acid also must be handled with care because of its corrosive properties.
H2SO4 has a wide range of uses. Most of it (�60%) is consumed in extracting phosphoric acid from apatites (phosphate rocks) for fertilizer use. Other industrial applications are in petroleum refining, cleaning agents, and chemical manufacturing. And of course, it is a staple in many laboratory procedures.
Sulfuric acid (98 wt%)Â hazard information
| Hazard class* | GHS code and hazard statement | |
|---|---|---|
| Corrosive to metals, category 1 | H290—May be corrosive to metals |  |
| Skin corrosion/irritation, category 1A | H314—Causes severe skin burns and eye damage | |
| Serious eye damage/eye irritation, category 1 | H318—Causes serious eye damage | |
*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. .
MOTW update
Apixaban1 was the Molecule of the Week for August 22, 2022. It is an anticoagulant drug used to treat or prevent blood clots. It was approved for use under the brand name Eliquis by the European Medicines Agency in 2011 and by the US Food and Drug Administration in 2012.
This past March, Isabelle Mahé at Paris Cité University (Colombes, France) and collaborators at 36 institutions in Europe and Canada reported the results of a 1766-patient, �12-month trial of the extended use of reduced-dose apixaban for cancer-associated venous thromboembolism. The authors found that recurrent venous thromboembolism occurred in a slightly lower percentage of cancer patients treated with reduced-dose apixaban, compared with those on the full dose. The reduced dose led to a lower incidence of clinically relevant bleeding complications than the full dose.
1. CAS Reg. No. 503612-47-3.
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Sulfuric acid fast facts
| CAS Reg. No. | 7664-93-9 |
| SciFindern name | Sulfuric acid |
| Empirical formula | H2O4S |
| Molar mass | 98.08 g/mol |
| Appearance | Viscous colorless liquid |
| Boiling point | 337 ºCa |
| Water solubility | Miscible |
a. Begins to decompose at �300 ºC.
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