50 Fun Facts About Acids and Bases

Which of these acids, sprayed by ants to defend their nests, is named after the Latin for 'ant'?

Formic acid takes its name from formica, the Latin for ant. English naturalist John Ray first isolated it in 1671 by distilling large numbers of the insects.

Which alchemists' mixture of two acids can dissolve gold, although neither acid manages it alone?

Aqua regia once hid two Nobel medals: in wartime Copenhagen, George de Hevesy dissolved them in it to keep the gold from the Nazis, then recovered the metal after the war.

Søren Sørensen devised the pH scale while he was head of the research laboratory of which brewery?

Carlsberg employed Sørensen to study how hydrogen ions affect proteins, and he wanted a simple way to express their concentration. The same laboratory isolated the yeast behind lager.

Which vegetable's juice is a homemade pH indicator, pink in acids and yellow in strong bases?

Red cabbage owes the trick to its anthocyanin pigment, which is magenta in acids, purple at the midpoint and shifts through blue towards yellow as a solution turns more basic.

Which garden shrub acts as a living pH test, blooming blue in acidic soil and pink in alkaline soil?

Hydrangea flowers turn blue only when acidic soil frees aluminium ions for the roots to absorb. Alkaline ground ties the metal up, so the same plant blooms pink.

Which baked snack gets its dark, glossy crust from a quick bath in lye before it goes in the oven?

Pretzels get their traditional skin and flavour from the Maillard browning reaction, which the strongly basic dip sets off on the surface of the dough.

Which element did Antoine Lavoisier name 'acid-maker', wrongly believing it was part of every acid?

Oxygen comes from Greek roots meaning 'acid producer'. The mistake surfaced when some strong acids proved to contain none of it, but by then the name had stuck.

Which of these acids, additive E338 on labels, gives Coca-Cola and other colas their sharp tang?

Phosphoric acid is why such drinks are sometimes called phosphate sodas, or simply phosphates. It also has the potential to erode teeth.

Which stone, used for classical statues and the Parthenon, is steadily eaten away by acid rain?

Marble reacts with acids so readily that vinegar is ruled out for cleaning it, and Harvard wraps some of its outdoor marble statues in waterproof covers every winter.

Which of these protein-rich kitchen staples is naturally alkaline rather than acidic?

Egg white is an alkaline solution, about 90% water with the rest mostly proteins such as albumins and globulins dissolved in it.

Which of the strong acids, known to alchemists as spirits of salt, is also made by the human stomach lining?

Hydrochloric acid brings the stomach's contents down to about pH 1 to 2, a barrier against swallowed microbes. The stomach shields itself behind a thick layer of mucus.

Which of the strong acids makes up the permanent clouds of Venus and is the electrolyte in car batteries?

Sulfuric acid is so central to manufacturing that a nation's output of it was long treated as a measure of its industrial strength. Most of it goes into fertiliser.

Which of the weak acids, diluted in water, gives vinegar its sour taste and pungent smell?

Acetic acid was probably the first acid people ever made in bulk, because vinegar has been produced since the third millennium BCE.

Which of these acids, the sour note in oranges and limes, is now made mostly by feeding sugar to a mould?

Citric acid switched from fruit to fermentation after World War I disrupted Italian fruit exports. Cultures of the black mould Aspergillus niger are still the main industrial route.

Which of these acids, made by bacteria fermenting sugars, gives yoghurt and sauerkraut their sour tang?

Lactic acid does two jobs in fermented foods: it supplies the sourness and it makes them keep, which is why sauerkraut has such a long shelf life.

Which of the weak acids, made when the gas in fizzy drinks dissolves, also makes clean rain slightly acidic?

Carbonic acid is the reason unpolluted rain still has a pH below 7. It is also unstable, constantly breaking back down into water and gas.

Which of these acids attacks glass so readily that it has to be stored in plastic containers?

Hydrofluoric acid counts as a weak acid in dilute solution, yet it is dangerous to handle because it attacks the calcium in bones.

Which of the strong acids stains human skin yellow on contact and is used mainly to make fertilisers?

Nitric acid turns skin yellow by reacting with keratin, the protein in skin and nails. Jewellers use a drop of it to show up low-carat alloys.

Which of these acids helps make rhubarb leaves poisonous, although the plant's stalks are safe to eat?

Oxalic acid caused real poisonings in Britain during World War I, when rhubarb leaves were mistakenly recommended as a food.

Ascorbic acid, a name coined to mean 'without scurvy', is the chemical name of which essential nutrient?

Vitamin C is something most animals make for themselves. Humans, other higher primates and guinea pigs carry a broken gene for it, so they have to get it from food.

Which strong base, commonly called lye, is used to make hard bar soap and to unblock drains?

Sodium hydroxide clears a blocked pipe by converting the fat and grease into soap, which then dissolves in water.

Which pungent gas, a weak base, is dissolved in water to make many household glass cleaners?

Ammonia is also the vapour released by smelling salts, where its sharp, irritating odour works as a respiratory stimulant.

Which kitchen powder, a mild base, foams up with vinegar in the classic school volcano experiment?

Baking soda foams because the reaction releases a gas, and the same bubbles make cakes rise when the powder meets an acid in the batter.

Which over-the-counter remedies, such as Tums, relieve heartburn by raising the pH inside the stomach?

Antacids simply cancel out what is already in the stomach. Unlike acid-reducing drugs, they do nothing to stop more being made.

Which crushed rock do farmers and gardeners spread on acidic soil to raise its pH?

Limestone reacts as a base in the ground. For the same reason, lakes that sit on it stay less acidic under polluted rain than lakes on silicate rock.

Before industrial chemistry, soap-makers got their alkali by soaking which material in water?

Wood ash was soaked in water and the liquid boiled dry in large iron pots, leaving a pale residue that became known as pot ash.

Alkaline batteries take their name from their electrolyte, which is a solution of which strong base?

Potassium hydroxide is the caustic liquid that seeps out when old cells leak, irritating skin and eyes, which is why batteries are best removed from devices going into storage.

Acids taste sour, but which taste is typical of bases, which also feel slippery to the touch?

Bitter is the taste, and the slippery feel has an unnerving cause: a strong base starts turning the natural oils on skin into soap.

Which Surrey town, home of the Derby horse race, gave its name to the bath salt magnesium sulfate?

Epsom drew crowds in the 17th century to a spring on its common, whose mineral-rich water was believed to have healing qualities.

Which crop is cooked in an alkaline solution, a step called nixtamalisation, before being ground for tortillas?

Maize cooked this way softens, sheds its hulls and gives up nutrients that help prevent pellagra, a deficiency disease.

Because the pH scale is logarithmic, how much more acidic is a solution of pH 3 than one of pH 4?

Ten times is the jump for every whole number on the scale, so a liquid at pH 2 holds 100,000 times the hydrogen ion concentration of pure water at pH 7.

Which body fluid is kept within a narrow, slightly basic pH range of 7.35 to 7.45?

Blood cannot stray far from that window: a pH below 6.9 or above 7.8 is usually lethal, so the lungs and kidneys adjust it constantly.

Litmus, the dye in classic acid-base test papers, is extracted from which group of organisms?

Lichens have supplied the dye since around 1300, when the Catalan physician Arnaldus de Villa Nova was already using litmus to study acids and bases.

What colour does blue litmus paper turn when it is dipped into an acid such as vinegar?

Red is the signal for acid, though chlorine gas can fool the test: it strips the colour from blue litmus altogether, a change that cannot be reversed.

Which laboratory indicator is colourless in acidic solutions but turns vivid pink in basic ones?

Phenolphthalein doubled as a laxative for over a century. That effect came to light around 1900, when the Hungarian government tried using it as a marker in wine.

What colour does universal indicator turn in pure water, at the midpoint of the pH scale?

Green sits in the middle of a rainbow of shades, because the indicator is a blend of several dyes. Most versions still follow a formula patented by Yamada in 1933.

Which of these household liquids is strongly basic, with a pH of 11 or higher?

Bleach must never be mixed with an acid: lowering its pH pushes the hypochlorite in it towards releasing toxic chlorine gas.

Which of these liquids is naturally slightly basic rather than acidic, with a pH of about 8?

Seawater slipped from an average surface pH of about 8.15 to 8.05 between 1950 and 2020, a drift that makes it harder for corals and shellfish to build skeletons and shells.

Which yellow spice works as a kitchen pH indicator, turning reddish-brown when it meets a base?

Turmeric owes the trick to its pigment curcumin. Paper steeped in the spice works as a ready-made test strip, staying yellow in acids.

Which term describes a solution with a pH of exactly 7, such as pure water at 25 °C?

Neutral means the two kinds of ion behind acids and bases are in exact balance. The figure depends on temperature: in hotter water the balance point drops below 7.

Which Swedish chemist, whose thesis on ions barely passed, defined acids as releasing hydrogen ions in water?

Svante Arrhenius had the last laugh: extensions of that poorly graded work won him the 1903 Nobel Prize in Chemistry, making him the first Swedish laureate.

In the Brønsted–Lowry theory, an acid is defined as a substance that donates which particle to a base?

Proton transfer was proposed in the same year, 1923, by two chemists working independently: Johannes Brønsted in Denmark and Thomas Lowry in England.

Which American chemist, who coined the word 'photon', defined an acid as an acceptor of an electron pair?

Gilbert N. Lewis collected 41 Nobel Prize nominations and never won, although several of the chemists he mentored at Berkeley did.

What sets a strong acid apart from a weak acid when each is dissolved in water?

It ionises completely, so every molecule splits into ions in the water. Strength is not concentration: a strong acid can be dilute, and a weak one concentrated.

Which term describes a substance, such as water, that can react as either an acid or a base?

Amphoteric behaviour is built into every amino acid, which carries an acidic group and a basic group on the same molecule.

Which type of solution keeps its pH almost steady when small amounts of strong acid or base are added?

A buffer usually pairs a weak acid with a salt of that acid, so whatever is added gets mopped up before the pH can move far.

Which laboratory technique adds a solution drop by drop from a burette until an indicator changes colour?

Titration owes much of its kit to Joseph Louis Gay-Lussac, who improved the burette and coined both that word and 'pipette' in an 1824 paper.

Which ion, written H3O+, is made when an acid hands a hydrogen ion to a water molecule?

Hydronium is not confined to the laboratory: it is abundant in the gas clouds between the stars and has been detected in the plasma tails of comets.

According to Pliny the Elder, which gem did Cleopatra dissolve in vinegar and drink to win a dinner-party bet?

A pearl is built from the same chalky mineral as a seashell, which reacts even with the weak acid in vinegar, so the chemistry of Pliny's tale holds up.

What name do chemists give to what is left of an acid once it has given up a hydrogen ion?

A conjugate base is weak whenever its parent acid is strong: a fragment that let its hydrogen ion go so readily has little pull to take one back.