Disulfuric Acid: Characteristics And Functions Of This Substance
We have all heard of sulfuric acid at some point, even in passing This extremely corrosive and dangerous substance is the most produced chemical compound in the world. It is particularly important in the petroleum industry, steel treatment, the manufacture of explosives, detergents and plastics and in the synthesis of fertilizers.
Without sulfuric acid, it would not be possible to power the wood and paper industries, many processes in textile factories or the production of batteries. Nor can we forget its role in the chemical industry, since it is necessary for the synthesis of other acids and sulfates vital for certain processes.
In other words, society would not be as we know it without sulfuric acid, since it plays essential tasks in the chemical industry, the oil industry and the agricultural field, among many other things. In any case, not all sulfur compounds are equally known. Here we pay attention to one much less familiar to the general population: disulfuric acid
Disulfuric acid, also known as pyrosulfuric acid or oleum, is a sulfur oxacid The term “oxacid” refers to any acid that contains oxygen in its composition, especially those that have in their chemical structure at least one hydrogen atom (H), one oxygen atom (O) and a variable element, this being X.
Disulfuric acid is the main component of fuming sulfuric acid or oleum, whose properties and uses we will explain in future sections. For now, we are left with that its chemical structure is H2SO7. This means that it is made up of two hydrogen atoms (H2), 7 oxygen atoms (O7) and two sulfur atoms (S2). The usual sulfuric acid, for its part, has two hydrogen atoms, one sulfur and four oxygen atoms (H2SO4).
It is also of interest to emphasize that this acid has a molar mass of 178.13 g·mol−1 and that its melting point is 36 degrees, a temperature that marks the change from a solid to a liquid state. There are other acids with the same formula “H2O·(SO3)x”, although these cannot be isolated under experimental conditions today.
Oleum characteristics
As we have said, disulfuric acid It is the main component of fuming sulfuric acid, also known as oleum The formula of this solution is ySO3·H2O, with “y” being the total molar mass of the sulfur trioxide (SO3) part. In any case, it can also be designated with the nomenclature “H2SO4·xSO3”, where “x” refers to the molar free sulfur trioxide content. When x=1 and y=2, the formula H2S2O7 is obtained, or in other words, that of disulfuric acid.
It may sound complex, but stick with the following idea: an oleum solution can have different properties depending on the percentage concentration of sulfuric acid and the aforementioned conformation gives rise to disulfuric acid, which occurs in solid form up to 36 degrees of temperature. environmental. As interesting as this whole conglomerate sounds on a chemical level, in any case, it is necessary to highlight that Disulfuric acid is rarely used in laboratory environments or industrial processes
Oleum is synthesized through a “contact process”, where oxygen groups are added to sulfur (S+O3, SO3) and then it is dissolved in a concentrated sulfuric acid (H2SO4). Perhaps a chemist would tear his hair out at seeing such a great oversimplification, but for informative purposes, we take the license to show you the union of both concepts:
Thus, the typical oleum or disulfuric acid is made with sulfur to which oxygen and concentrated sulfuric acid have been added. In the world of chemistry, in the end everything is also a matter of mathematical knowledge.
Functions and uses of this substance
Once we have dissected the chemical nature of this complex solution, we can explore its uses, even if only briefly.
1. Production of sulfuric acid
Although it may sound counterintuitive, a solution that requires sulfuric acid for its synthesis can be useful for the production of sulfuric acid itself
Because of its high enthalpy of hydration (change in enthalpy when one mole of ions is dissolved in enough water to give a dilute solution), oleum can be diluted in water to produce additional concentrated sulfuric acid.
On the contrary, if SO3 were added directly to water, a gaseous film of sulfuric acid would form that is very difficult to handle.
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2. Transport intermediary
Since oleum occurs in a solid state up to a temperature of 36 degrees, It can be useful for transporting sulfuric acid in trucks with tanks, between oil refineries and various industries Once it reaches its destination, the oleum can be transformed back into its liquid state. In any case, this process must be carried out very carefully, since overheating of the material exceeds the safety limits.
Furthermore, oleum or disulfuric acid is less corrosive than conventional sulfuric acid when coming into contact with metals, since there are no free water molecules that can attack these surfaces. For this reason, it is sometimes also chosen to synthesize liquid disulfuric acid for transport between complex pipelines. Due to its ability to “revert” into concentrated sulfuric acid and its ease of changing from solid to liquid state, oleum has many uses in the field of transportation.
The oleum too It is used in the synthesis of explosives, with the notable exception of nitrocellulose This is because solutions of nitric acid (NO3) and sulfuric acid (H2SO4, which may or may not be obtained using disulfuric acid as a base) contain notable amounts of water, something that makes them of little use in many explosive manufacturing processes. .
4. Use in the study of organic chemistry
Oleum is an aggressive and highly corrosive reactive agent, useful as an intermediate in certain chemical reactions.
Summary
In summary, disulfuric acid can be seen as an intermediate of sulfuric acid, despite being derived from reactions that require it in the first instance. As it occurs naturally in a solid state, it is indicated for safe transportation in many industry sectors that handle H2SO4 naturally. The use of this compound in its liquid form is also very interesting, since being less corrosive than sulfuric acid, it generates less damage to pipes and other metal coatings.
Again, we return to the idea that sulfuric acid is essential in the agricultural, lumber, textile, oil industry and many other branches. Thus, although disulfuric acid is not very useful as a compound directly applicable in the laboratory, it does provide a certain plasticity when transporting, refining and treating the sulfuric acid itself.
