The term acid comes from the latin word acetum and the Greek word oxein. Both mean "sour", which betrays the fact that, for many centuries, acidity was only measured using our sense of taste (possibly dangerously so) much like pungency today.
Lavoisier (1743-1794) In 1777, Antoine Lavoisier (1743-1794) thought that the newly-discovered active component of air (Sheele 1773, Priestley 1774) was the long-sought-after "universal acidifying principle". Accordingly, he coined the name oxygen for it (i.e., "generator of acidity", using the aforementioned Greek etymology). As it takes oxygen to turn wine into vinegar or to produce organic acids from other alcohols, Lavoisier guessed that oxygen was essential to acidity. This misguided theory survived long enough for the name oxygen to be universally accepted, in spite of its dubious etymology.
Berzelius (1779-1848) Jacob Berzelius (1779-1848) upheld the same misconception in his theory of electrochemical dualism, as he argued that acids were oxides of non-metals and bases were oxides of metals...
Humphry Davy (1778-1829) In 1810 however, Humphry Davy (1778-1829) showed that muriatic acid doesn't contain any oxygen, by discovering the elemental nature of chlorine (which had been thought to be an "oxide of muriaticum" by Scheele, when he isolated it, in 1774).
Thereafter, the acids fitting the structure envisioned by Lavoisier were dubbed oxacid (French: oxacide ) . The modern term is oxoacid or oxy-acid. The other acids were dubbed hydracids.
Justus von Liebig (1803-1873) In 1838, Justus von Liebig (1803-1873) defined acids as compounds containing an hydrogen which can be replaced by a metal.
In 1884, Svante Arrhenius (1859-1927) suggested, in his doctoral dissertation, that some substances are ionized in solution. The ideas of Arrhenius were ahead of his time (he only earned a fourth-class degree with that thesis) but he would eventually get a Nobel prize for the work (1903).
In 1887, Arrhenius used the electrolytic theory of dissociation he had introduced in his thesis to formally define an acid as a substance that dissociates in water into anions and hydrogen ions. Conversely, he view a base as a substance dissociating into a cation and an hydroxide ion (OH-). Although this was a great breakthrough, this definition only applies to aqueous solutions. It fails to recognize the acidity of insoluble substances.
In 1909, using the definition of Arrhenius, Søren Sørensen (1868-1939) introduced the pH scale to quantify the acidity of aqueous solutions.
In 1923, ... ...
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Acid-Base History
|
A Brief History of Acidity
by John W. Nicholson (January 2004).
A
Basic History of Acid by Mark S. Lesney
(American Chemical Society, 2003).
Wikipedia :
Acid-base chemistry
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Acid-base reaction theories
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Acid
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Base
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Hydronium Solvation
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Acid-base titration
Safety Poster
Two rhyming mnemonics for the safer way to dilute an acid:
French : Acide dans l'eau, bravo.
Eau dans l'acide, suicide.
English : Do like you oughta, add acid to water.
Ferdinand Hoefer (1811-1878) has attributed the initial discovery of muriatic acid to the alchemist Mary the Jewess (third century AD).
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Wikipedia : Hydrochloric acid | Gastric acid
Vitriol was the name of the salts of 3 common metals (M) that dissolve in water as metal aquo complexes M(H2O)6++ and sulfate ions SO4- -.
The corresponding acid (H2SO4 ) was properly called vitriolic acid in aqueous solution, or oil of vitriol in its viscous concentrated form. The latter was also improperly shortened to vitriol.
The invention of vitriol is usually attributed to Geber (c. AD 721-815). It may have been known to the Assyrians much earlier.
H2SO4 protonates water molecules very easily. In a dilute aqueous solution, sulfuric acid is essentially just a diprotic acid. It's a strong acid with respect to its first ionization (i.e., un-ionized sufuric acid is virtually nonexistent in water) and a weak acid with respect to the second ionization:
H2SO4 + H2O
«
H3O+ + HSO4-
( K = 2.4 10+6 at 25°C )
HSO4- + H2O
«
H3O+ + SO4- -
( K = 1.0 10-2 at 25°C )
Without water, pure sulfuric acid is an oily substance which is a powerful solvent that undergoes an autoprotolysis similar to that of water:
2 H2SO4 « H3SO4+ + HSO4- ( K = 2.7 10-4 at 25°C )
However, the analogy stops here, since pure H2SO4 actually contains many other chemical species in equilibrium, as listed below. The first entry is the result of subtracting all the other concentrations from 10195.9 mmol/kg, the reciprocal of the nominal molar mass of H2SO4 (98.0785 g/mol).
The above concentrations at chemical equilibrium correspond to the following dimensionless equilibrium constants (cf. mass-action law) if we equate chemical affinities and concentrations (as an approximation).
The above equilibrium is properly described as 100% sulfuric acid.
H2S2O7 can be viewed as sulfuric gas (SO3) dissolved in vitriol oil :
H2SO4 + SO3 « H2S2O7
If more trioxide is dissolved than called for by the stoichiometry of pure sulfuric acid, then we effectively have sulfuric acid rated at more than 100%, because adding water to it would yield 100% sulfuric acid! Such stuff is called oleum or fuming sulfuric acid (the vapor is mostly sulfur trioxide).
For better stability in storage, commercial concentrated sulfuric acid is usually rated at 98% (under 1 atm, there's an azeotrope at 98.3%, which boils at 338°C).
By definition, 20% oleum is 20 kg of SO3 (80.0632 g/mol) dissolved in 80 kg of H2SO4 (98.0785 g/mol).
Wikipedia : Sulfuric acid | Strong acids | Diprotic acids | Mineral acids
Commercial concentrated nitric acid is 68% HNO3 which actually forms an azeotrope with water, boiling at 120.5 ーC under 1 atm.
One of the earliest extant recipes for the preparation of nitric acid is the distillation of a mixture of niter (saltpeter; KNO3 ) green vitriol ( FeSO4 ) and alum. This appears in De Inventione Veritatis (part of the Pseudo-Geber corpus, attributed to the Franciscan alchemist Paul of Tarento, who was active in the second half of the thirteenth century). Albertus Magnus (1205-1280) Related early recipes (heating niter and clay together) are described by Albertus (1205-1280) and Ramon Llull (c.1232-1316).
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Wikipedia : Nitric acid | Oxidizing acid
Commercially available at a 72.5% concentrantion which forms an azeotrope with water at 1 atm, boiling at 203°C (indefinitely stable but hygroscopic).
Perchloric acid was first obtained in 1816, by the Austrian Count Friedrich von Stadion, who observed the formation of potassium perchlorate by the action of sulfuric acid on potassium chlorate. An aqueous solution of perchloric acid results from the distillation of that mixture.
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Wikipedia : Perchloric acid | Oxidizing acid
Simplest examples are formic acid HCOOH and acetic acid CH3COOH.
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By dehydration, a carboxylic acid RCOOH gives a symmetrical anhydride (RCO)2O. Acetic anhydride (CH3CO)2O is the simplest stable example at room temperature, since formic anhydride decomposes at 24°C.
The simplest example of an asymmetrical carboxylic anhydride is acetic-formic anhydride.
Wikipedia : Carboxylic acids | Organic acid anhydride
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Wikipedia : Picric acid
Para-toluene-sulfonic acid or PTSA (CAS 104-15-4) is also called tosylic acid. It is a non-oxydizing strong acid (pKa = -2.8 in water) which is well-suited to the preparation of standard titration solutions because it's a soluble solid which can be conveniently weighed (172.202 g/mol).
The negative pKa indicates a high dissociation constant in water:
[ H3O+ ] [ CH3C6H4SO3- ] / [ CH3C6H4SO2(OH) ] = Ka = 630
Many other sulfonic acids are even much stronger than that:
Being combinations of an halogen atom with a sulfonic group, these are best called halosulfonic acids. The alternate -sulfuric suffix merely evokes the structural similarity with the molecule of sulfuric acid.
Fluorosulfuric acid FSO2(OH) is the strongest sulfonic superacid and one of the strongest acids commercially available.
Chlorosulfuric acid ClSO2(OH) reacts violently with water to yield hydrochloric acid and sulfuric acid:
ClSO3H + H2O ® HCl + H2SO4
Bromosulfonic acid is a solid which decomposes at 8°C :
2 BrSO3H ® Br2 + H2SO4 + SO2
Iodosulfonic acid has apparently never been synthesized.
Triflic acid (trifluoromethanesulfonic acid) CF3SO2(OH) is a superacid first synthesized in 1954 by Robert N. Haszeldine (b. 1925) and J.M. Kidd.
Wikipedia : Sulfonic acids | P-Toluenesulfonic acid
This is a moderately strong acid: pKa = 1.05
In its solid form, sulfamic acid can be conserved indefinitely at room temperature. Because the crystals are not hygroscopic, they can be weighed accurately to prepare standard solutions used in acidimetry. For best accuracy, such solutions must be used promptly, as sulfamic acid degrades (slowly) when dissolved in water.
The standard procedure is to calibrate a loosely prepared solution of a strong base (e.g. NaOH) by titration of a solution containing a precisely-measured mass of sulfamic acid crystals. (The volume of water used to dissolve the sulfamic acid is largely irrelevant but the crystals should be as pure as possible.) The basic solution so calibrated cam then be used for the titration of other acidic solutions.
Sulfamic acid is considered a safe acidic cleaning agent for household use, mostly because (unlike stronger acids) it will not produce dangerous chlorine gas when accidentaly mixed with hypochlorite products.
Wikipedia : Sulfamic acid
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Wikipedia : Brønsted-Lowry acid-base theory | Protonation | Deprotonation | Hydronium
Arguing that only hydrogen compounds can be acids would be
like
arguing that only oxygen compounds can be oxidizing agents.
Gilbert N. Lewis (1940, paraphrased)
According to G.N. Lewis, an acid (A) and a base (B:) form an adduct AB, where the bond between A and B is a dative covalent bond (both electrons come from the base).
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Lewis was nominated 35 times for the Nobel Prize in Chemistry.
Wikipedia : Lewis acids and bases | Octet rule | Gilbert N. Lewis (1875-1946)
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Wikipedia : Acidity functions | Hammett acidity function | Louis Plack Hammett (1894-1987)
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Wikipedia :
Superacids
|
Carborane
Superacid Chemistry
by George Andrew Olah (2009)
In aqueous solution, the hydroxide ion OH- has the highest basicity but there are compound that have greater proton affinity in dry environments.
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Wikipedia : Superbases | Hydroxide ion | Lithium diisopropylamide (LDA)
The strongest known superacid is fluoroantimonic acid H2F(SbF6).
Some of the Strongest Known Acids (H0 = Hammett function)
Wikipedia :
Fluorosulfuric acid
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Triflic acid
|
Leveling effect
Strongest acid known? (Science Forums)
The strongest acid in the world: Fluoroantimonic acid
(26:35) by ChemicalForce (2020年12月17日).
