pH Comparison

[Please note first]

This app cannot work out a pH for you; a phone has no sensor for it.

It says nothing about what is good for your skin, your hair or your health,

and it gives no advice on handling household chemicals. You enter a pH you

already know, and it is set against values that are already fixed.

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≒ pH Comparison - how acidic is that, really?

"pH 5.6" tells you almost nothing on its own. It is the pH of ordinary rain:

carbon dioxide from the air dissolves into it, so even clean rain never

settles at neutral.

Enter one pH and set it against 22 things, from stomach acid to drain cleaner.

■ One step is ten times

The scale is evenly spaced; what it counts is not.

Black coffee (5.0) and pure water (7.0) are only 2 apart, yet they differ

100-fold in hydrogen ions. Stomach acid (1.5) and drain cleaner (13.5) are

12 apart: 10 to the 12th power, a trillion times over.

Every row carries its own figure against pure water. Stomach acid is about

320,000 times, black coffee exactly 100 times, soapy water exactly 1/1000.

■ Ordinary rain is already acidic

Carbon dioxide from the air dissolves into rain, so even clean rain settles

at about pH 5.6. Acid rain is therefore reckoned from 5.6 downwards, not

from 7. Against pure water that is about 25 times the hydrogen ions.

■ Blood moves by only 0.1

Of the 19 entries that carry a range, 17 span 0.4 or more, and shampoo and

soapy water span 2.0. Human blood runs from 7.35 to 7.45, a spread of 0.1.

The next narrowest after blood is cola, at 0.2.

The body holds itself inside that narrow band. You only see it once

everything is lined up together.

■ Twenty-two things

Stomach acid 1.5, a strongly acidic hot spring 2.1, lemon juice 2.3,

cola 2.5, vinegar 2.9, wine 3.4, orange juice 3.7, tomato juice 4.2,

beer 4.4, black coffee 5.0, shampoo 5.5, ordinary rain 5.6, milk 6.7,

pure water at 25 °C 7.0, human blood 7.4, seawater 8.1, baking soda in

water 8.4, an alkaline hot spring 9.5, soapy water 10.0, limewater 12.4,

chlorine bleach 12.5 and drain cleaner 13.5.

Tap any row to load its pH.

■ A range is not a margin of error

The pH of food and drink shifts with variety, origin and preparation.

The range under a name is how much it varies with conditions, not an error

bar, and every comparison is worked out from a single typical value.

Searching by range would let the widest entries swallow everything around

them, and blood, with its 0.1, would almost never come up at all.

■ Good for

▪ Making sense of a pH figure from the news or a science lesson

▪ Explaining acids and alkalis to a child

▪ Any moment you see a number and wonder how sour that really is

■ Things worth knowing (included in the app)

▪ One step of pH is ten times the hydrogen ions; 5 and 7 are 2 apart and

differ 100-fold

▪ Ordinary rain is pH 5.6, and acid rain is reckoned below that

▪ Human blood moves only from 7.35 to 7.45, a spread of 0.1

▪ Japanese labelling rules define these words for detergents and soaps,

but nothing defines them for cosmetics

▪ pH counts hydrogen ions - not how concentrated an acid is, and not how

dangerous it is

▪ Seven is neutral at 25 °C; pure water at 60 °C sits near 6.5, still neutral

■ How the app is built

▪ A single screen and no settings page

▪ Your last five entries are kept and can be tapped to restore

▪ One tap copies the result

▪ Japanese and English, following your device language

▪ No account needed. The comparison runs on your device and the pH you type is never sent anywhere

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Note: the pH of food and drink shifts with variety, origin and preparation,

so these are typical values with the ranges commonly seen. This app cannot

work out a pH for you and says nothing about skin or health. It only sets a

number you enter against values that are already fixed.