Home and Garden pH Indicators

July 25, 2014 – 09:34 pm

There are many common household products and garden plants that can be used as pH indicators. Most plants contain pH sensitive anthocyanins, so experiment with other plants, too. Many of these natural pH indicators exhibit a broad range of colors.

Plants

  • Beets
    A very basic solution will change the color of beets or beet juice from red to purple.
  • 'Black' Berries
    Blackberries, black currants, and black raspberries change from red in an acidic environment to blue or violet in a basic environment.
  • Blueberries
    Blueberries are blue around pH 2.8-3.2, but turn red as the solution becomes even more acidic.
  • Carrots
  • Cherries
    Cherries and their juice are red in an acidic solution, but turn blue to purple in a basic solution.
  • Curry Powder
    Curry contains the pigment curcumin, which changes from yellow at pH 7.4 to red at pH 8.6.
  • Delphinium Petals
    The anthocyanin delphinin changes from bluish-red in an acidic solution to violet blue in a basic solution.
  • Geranium Petals
    Geraniums contain the anthocyanin pelargonin, which changes from orange-red in an acidic solution to blue in a basic solution.
  • Grapes
    Red and purple grapes contain multiple anthocyanins. Blue grapes contain a monoglucoside of malvinidin which changes from deep red in an acidic solution to violet in a basic solution.
  • Horse Chestnut Leaves
    Soak horse chestnut leaves in alcohol to extract the fluorescent dye esculin. Esculin is colorless at pH 1.5 but becomes fluorescent blue at pH 2. Get the best effect by shining a black light on the indicator.
  • Morning Glories
    Morning glories contain a pigment named 'heavenly blue anthocyanin' which changes from purplish-red at pH 6.6 to blue at pH 7.7.
  • Onion
    Onions are olfactory indicators. You don't smell onions in strongly basic solutions. Red onion also changes from pale red in an acidic solution to green in a basic solution.
  • Pansy Petals
  • Petunia Petals
    The anthocyanin petunin changes from reddish-purple in an acidic solution to violet in a basic solution.
  • Poison Primrose
    Primula sinensis has orange or blue flowers. The orange flowers contain a mixture of pelargonins (see Geranium). The blue flowers contain malvin, which turns from red to...
Red cabbage juice can be used to test the pH of common household chemicals.

Source: chemistry.about.com


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