Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

pH - Basic (alkaline) vs. Acidic

Sponsored Links

pH can be viewed as an abbreviation for power of Hydrogen - or more completely, power of the concentration of the Hydrogen ionin a liquid.

The mathematical definition of pH is a bit less intuitive but in general more useful. It says that the pH is equal to to the negative logarithmic value of the Hydrogen ion (H+) concentration, or

pH = -log [H+]

pH can alternatively be defined mathematically as the negative logarithmic value of the Hydroxonium ion (H3O+) concentration. Using the Bronsted-Lowry approach

pH = -log [H3O+]

pH values are calculated in powers of 10. The hydrogen ion concentration in a solution with pH 1.0 is 10 times larger than the hydrogen concentration in a solution with pH 2.0. The larger the hydrogen ion concentration - the smaller the pH.

  • when the pH is above 7 the solution is basic (alkaline)
  • when the pH is below 7 the solution is acidic

In pure neutral water the concentration of hydrogen and hydroxide ions are both 10-7 equivalents per liter.

pH - Ion Concentration
pHIon Concentration (gram equivalent per liter)Type of Solution
0 1.0 Acid Solution
- Hydrogen ions -
1 0.1
2 0.01
3 0.001
4 0.0001
5 0.00001
6 0.000001
7 0.0000001 Neutral Solution (pure neutral water)
8 0.000001 Basic (alkaline) Solution
- Hydroxide ions -
9 0.00001
10 0.0001
11 0.001
12 0.01
13 0.1
14 1.0

Download and print pH Ion Concentration Chart


Some common Products and their pH Values

pH values in some common products:

pH in Common Products
Battery Acid 0
HCl in stomach acid 1
Lemon juice, vinegar 2-3
Orange juice 3-4
Acid rain 4
Black coffee 5
Urine, saliva 6
Pure water 7
Sea water 8
Baking soda 9
Ammonia solution 10-11
Soapy water 12
Bleach 13
Oven cleaner 13-14
Drain cleaner 14

Acid-Base Indicators

pH - Acid-Base Indicators
IndicatorpH - RangeColor Cange
Thymol blue 1.2 - 2.8 red yellow
Pentamethoxy red 1.2 - 2.3 red - violet colorless
Tropeolin 1.3 - 3.2 red yellow
2,4 - Dinitrophenol 2.4 - 4.0 colorless yellow
Methyl yellow 2.9 - 4.0 red yellow
Methyl orange 3.1 - 4.4 red orange
Congo red 3.0 - 4.2 blue-violet red-orange
Bromphenol blue 3.0 - 4.6 yellow blue - violet
Tetrabromphenol blue 3.0 - 4.6 yellow blue
Alizarin sodium sulfonate 3.7 - 5.2 yellow violet
α - Naphthyl red 3.7 - 5.0 red yellow
p - Ethoxychrysoidine 3.5 - 5.5 red yellow
Bromcresol green 4.0 - 5.6 yellow blue
Methyl red 4.4 - 6.2 red yellow
Bromcresol purple 5.2 - 6.8 yellow purple
Chlorphenol red 5.4 - 6.8 yellow red
Bromphenol blue 6.2 - 7.6 yellow blue
p - Nitrophenol 5.0 - 7.0 colorless yellow
Litmus 5.0 - 8.0 red blue
Azolitmin 5.0 - 8.0 red blue
Phenol red 6.4 - 8.0 yellow red
Neutral red 6.4 - 8.0 red yellow
Rosolic acid 6.8 - 8.0 yellow red
Cresol red 7.2 - 8.8 yellow red
α - Naphtholphthalein 7.3 - 8.7 rose green
Tropeolin 7.6 - 8.9 yellow rose - red
Thymol blue 8.0 - 9.6 yellow blue
Phenolphthalein 8.0 - 10.0 colorless red
α - Naphtholbenzein 9.0 - 11.0 yellow blue
Thymolphthalein 9.4 - 10.6 colorless blue
Nile blue 10.1 - 11.1 blue red
Alizarin yellow 10.0 - 12.0 yellow lilac
Salicyl yellow 10.0 - 12.0 yellow orange - brown
Diazo violet 10.1 - 12.0 yellow violet
Tropeolin 11.0 - 13.0 yellow orange - brown
Nitramine 11.0 - 13.0 colorless orange - brown
Poirrier's blue 11.0 - 13.0 blue violet - pink
Trinitrobenzoic acid 12.0 - 13.4 colorless orange - red
Sponsored Links

Related Topics


Basic engineering data. SI-system, unit converters, physical constants, drawing scales and more.


Engineering related topics like Beaufort Wind Scale, CE-marking, drawing standards and more.

Related Documents

Acid and Base pH Indicators

pH range vs. color change for acid and base indicators - together with pKa and structures of the indicators.

Acids - pH Values

pH values of acids like sulfuric, acetic and more..

Alcohols and Carboxylic Acids - Physical Data

Molweight, melting and boiling point, density, pKa-values, as well as number of carbon and hydrogen atoms in molecules are given for 150 different alcohols and acids.

Amines, Diamines and Cyclic Organic Nitrogen Compounds - pKa Values

Values for the negative logarithm of the acid dissociation constant, pKa, of the conjugated acid of amines, diamines and cyclic organic nitrogen compounds, shown together with the molecular structure of the acids.

Bases - pH Values

pH values for bases like sodium hydroxide, ammonia and more.

Food and Foodstuff - pH Values

pH in common food products - like apples, butter, wines and more.

Inorganic Acids and Bases - pKa Values

Values for the negative logarithm of the acid dissociation constant, pKa, of inorganic acids and bases, as well as hydrated metal ions.


The rules of logarithms - log10 and loge for numbers ranging 1 to 1000.

pH in Human Biological Material

pH in human materials like blood, salvia and more.

Phenols, Alcohols and Carboxylic Acids - pKa Values

For oxygen containing organic compounds this is given: pKa (the negative logarithm of the acid dissociation constant), molecular structures, molar weights, density and melting and boiling points.

Strong and Weak Acids and Bases

The most common strong acids and bases, and some examples of weak acids and bases, together with definition of strong and weak acids and bases.

Sulfuric Acid - Density

Density of sulfuric acid at various temperatures and concentrations.

Sponsored Links

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.