Acids and Bases in Your Home

You don’t need a laboratory to find acids and bases. An ordinary home contains dozens of them, from the lemon in the fruit bowl to the cleaner under the sink. Knowing which is which explains why vinegar removes limescale, why baking soda calms indigestion, and why some cleaning products must never be mixed.

Here’s a room-by-room tour. The pH values are typical; real products vary with brand and concentration.

The kitchen

Item	Acid or base	Main chemical	Typical pH
Lemon and lime juice	acid	citric acid	2.0–2.6
Vinegar	acid	ethanoic (acetic) acid, about 5%	2.4–3.0
Cola	acid	phosphoric acid, carbonic acid	2.5–3.0
Orange juice	acid	citric and ascorbic acid	3.3–4.2
Tomatoes	acid	citric and malic acid	4.3–4.9
Black coffee	weak acid	chlorogenic and other acids	about 5
Milk	very weak acid	lactic acid, phosphates, proteins	6.5–6.8
Egg white	base	proteins; loses CO₂ with age	7.6 fresh, up to about 9.2 when older
Baking soda (dissolved)	weak base	sodium hydrogencarbonate	about 8.3
Baking powder	acid + base mix	NaHCO₃ plus a dry acid (e.g. cream of tartar)	releases CO₂ when wet

Why it matters:

• Baking relies on acid–base reactions. Baking soda reacts with acidic ingredients (buttermilk, yoghurt, lemon, honey, cocoa) to release carbon dioxide, which makes cakes rise. Baking powder contains both the base and a dry acid, so it only needs water and heat.
• Acid preserves food. Pickling in vinegar lowers the pH enough to stop most bacteria growing. Lemon juice keeps cut apples and avocados from browning by slowing the enzyme responsible.
• Egg whites get more alkaline as they age, because carbon dioxide escapes through the shell. That’s one reason old eggs peel more easily after boiling.

The bathroom

Item	Acid or base	Main chemical	Typical pH
Limescale remover	acid	citric, sulfamic, phosphoric or hydrochloric acid	1–3
Toilet cleaner	often acid	hydrochloric or other acids	1–2
Hand soap	base	salts of fatty acids	9–10
“pH-balanced” body wash	weakly acidic	synthetic detergents with citric acid buffer	5–6
Toothpaste	usually neutral to basic	calcium carbonate, hydrated silica, sodium fluoride	7–9
Shampoo	usually weakly acidic	detergents + citric acid	5–7

Why it matters:

• Limescale is mainly calcium carbonate, left behind by hard water. Acids dissolve it: CaCO₃ + 2H⁺ → Ca²⁺ + H₂O + CO₂. The fizzing you sometimes see on a scaled kettle element is carbon dioxide. The reactions of acids with carbonates are covered in acids vs bases.
• Skin is slightly acidic (the “acid mantle”, pH around 4.5–5.5), which helps protect it from some microbes. Traditional soap is alkaline, so some people with sensitive skin prefer pH-balanced cleansers.
• Shampoos and conditioners are often slightly acidic because acidic conditions help the cuticle scales on hair lie flat, making hair feel smoother.

The laundry and utility room

Item	Acid or base	Main chemical	Typical pH
Laundry detergent	base	surfactants, sodium carbonate	9–11
Washing soda	base	sodium carbonate	about 11
Household ammonia	weak base	ammonia solution	11–11.6
Bleach	base	sodium hypochlorite + a little NaOH	11–13
Oven cleaner	strong base	sodium hydroxide	13–14
Drain unblocker	strong base (usually)	sodium hydroxide or potassium hydroxide	13–14

Why it matters:

• Alkalis cut grease. Strong bases react with fats and oils to turn them into soap (saponification), which then washes away. That’s how oven cleaners and drain unblockers work.
• Washing soda softens water by precipitating the calcium and magnesium ions that stop detergents lathering: Ca²⁺ + CO₃²⁻ → CaCO₃.
• Bleach is kept alkaline because hypochlorite is more stable at high pH.

The medicine cabinet

Item	Acid or base	Main chemical	Notes
Antacid tablets	base	calcium carbonate, magnesium hydroxide, aluminium hydroxide	neutralise excess stomach acid
Milk of magnesia	base	magnesium hydroxide suspension	pH about 10.5; also a laxative
Aspirin	acid	acetylsalicylic acid	pKa about 3.5
Vitamin C tablets	acid	ascorbic acid	often fizzy (with a carbonate)
Effervescent tablets	acid + base	citric acid + sodium hydrogencarbonate	fizz on contact with water
Bite and sting relief	depends	varies	old advice: vinegar for wasp stings, bicarbonate for bee stings (not well supported)

Why it matters:

• Antacids use weak, mostly insoluble bases so they neutralise acid gently without making the stomach strongly alkaline. Read more in stomach acid chemistry.
• Effervescent tablets are a dry mixture of an acid and a carbonate. Nothing happens until water lets the ions move, and then CO₂ fizzes out. The same chemistry powers bath bombs.

The garden

Item	Acid or base	Main chemical	Notes
Garden lime	base	calcium carbonate or calcium hydroxide	raises soil pH
Ericaceous compost	acidic	peat or pine-based materials	for acid-loving plants
Sulfur chips or aluminium sulfate	acidify soil	S (oxidised by bacteria to sulfuric acid) or Al³⁺	lowers soil pH
Ammonium-based fertiliser	slightly acidifying	ammonium sulfate, ammonium nitrate	acidifies soil over time
Wood ash	base	potassium and calcium carbonates	mild liming effect

Soil pH controls which nutrients plants can absorb. Most garden plants prefer pH 6–7. Blueberries, rhododendrons and azaleas prefer more acidic soil, around 4.5–5.5. Hydrangeas are the famous example: blue flowers in acidic soil, pink in alkaline soil.

The living room and beyond

Acids and bases turn up in less obvious places too. Car batteries contain sulfuric acid, which is why they’re labelled corrosive. Old-fashioned photographic chemicals, plaster, cement and mortar are strongly alkaline when wet, and fresh concrete can cause chemical burns if it’s left on bare skin. Aquarium owners test and adjust water pH for their fish, and swimming pools are kept close to pH 7.4 using sodium hydrogensulfate to lower pH or sodium carbonate to raise it.

Safety: the golden rules

1. Never mix bleach with acids. Acidic cleaners (many toilet and limescale cleaners) react with bleach to release chlorine gas, which is toxic.
2. Never mix bleach with ammonia. This produces chloramines, which are also toxic.
3. Don’t mix different cleaning products at all unless the label says it’s safe.
4. Store products in their original containers, never in drinks bottles.
5. Wear gloves and eye protection with oven cleaners, drain unblockers and strong limescale removers. Alkali splashes in the eye need rinsing with running water for at least 15 minutes and urgent medical attention.
6. Ventilate the room when using strong cleaning products.

A simple home experiment

Using red cabbage juice as an indicator, you can test many of the items above safely (skip the strong cleaners). Arrange them in order from most acidic to most alkaline and compare your results with the tables here. Instructions are in make a red cabbage pH indicator.

Key takeaways

• Kitchens are full of acids (citrus, vinegar, cola) and a few mild bases (baking soda, egg white).
• Acids remove limescale; alkalis remove grease; that’s why cleaners come in both types.
• Antacids and effervescent tablets are everyday acid–base reactions.
• Soil pH decides which plants thrive, and can be adjusted with lime or sulfur.
• Never mix bleach with acids or ammonia.
• For more on the pH scale behind these numbers, see the pH scale explained.