dvr Acid Base INDICATOR

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.
Plants
%u2022Beets
A very basic solution will change the color of beets or beet juice from red to purple.

%u2022'Black' Berries
Blackberries, black currants, and black raspberries change from red in an acidic environment to blue or violet in a basic environment.

%u2022Blueberries
Blueberries are blue around pH 2.8-3.2, but turn red as the solution becomes even more acidic.

%u2022Carrots / Cherries
Cherries and their juice are red in an acidic solution, but turn blue to purple in a basic solution.

%u2022Curry Powder
Curry contains the pigment curcumin, which changes from yellow at pH 7.4 to red at pH 8.6.

%u2022Delphinium Petals
The anthocyanin delphinin changes from bluish-red in an acidic solution to violet blue in a basic solution.

%u2022Geranium Petals
Geraniums contain the anthocyanin pelargonin, which changes from orange-red in an acidic solution to blue in a basic solution.

%u2022Grapes
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.

%u2022Horse 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.

%u2022Morning 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.

%u2022Onion
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.

%u2022Pansy Petals

%u2022Petunia Petals
The anthocyanin petunin changes from reddish-purple in an acidic solution to violet in a basic solution.

%u2022Poison 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 purple as a solution goes from acidic to basic.

%u2022Poppy Petals

%u2022Purple Peonies
Peonin changes from reddish-purple or magenta in an acidic solution to deep purple in basic solution.

%u2022Red (Purple) Cabbage
Red cabbage contains a mixture of pigments used to indicate a wide pH range.

%u2022Red Radish

%u2022Rhubarb

%u2022Rose Petals
The oxonium salt of cyanin turns from red to blue in basic solution.

%u2022Strawberries

%u2022Tea

%u2022Thyme Extract in Alcohol

%u2022Turmeric
This spice contains a yellow pigment, curcumin, which changes from yellow at pH 7.4 to red at pH 8.6.

%u2022Tulip Petals

%u2022Violet Petals

 

Household Chemicals

%u2022Baking Soda (NaHCO3)
Baking soda will fizz when added to an acidic solution (such as vinegar), but will not fizz in an alkaline solution. The reaction doesn't readily reverse itself, so baking soda can be used to test a solution, but can't be 'reused'. The reaction is:
HCO3-(aq) + H+(aq) = H2O(l) + CO2(g)

%u2022Colorchange Lipstick
You'll need to test your colorchange lipstick to determine its pH range, but most cosmetics that change color respond to changes in pH (different from cosmetics that change color according to angle of light).

%u2022ExLax Tablets
The tablets contain contain phenolphthalein, which is a pH indicator that is colorless in solutions more acidic than pH 8.3 and pink to deep red at solutions more basic than pH 9.

%u2022Vanilla Extract
Vanilla extract is an olfactory indicator. You can't smell the characteristic scent at high pH (alkaline solution) because the molecule is in its ionic form.

%u2022Washing Soda
As with baking soda, washing soda fizzes in an acidic solution but not in a basic solution.

Application:

What is an acid-base indicator ?
An acid-base indicator is a weak acid or a weak base. The undissociated form of the indicator is a different color than the iogenic form of the indicator. An Indicator does not change color from pure acid to pure alkaline at specific hydrogen ion concentration, but rather, color change occurs over a range of hydrogen ion concentrations. This range is termed the color change interval. It is expressed as a pH range.

 

Principle / Mechanism of Indicator :
Weak acids are titrated in the presence of indicators which change under slightly alkaline conditions. Weak bases should be titrated in the presence of indicators which change under slightly acidic conditions.

 

Common acid-base indicators :
Several acid-base indicators are listed below, some more than once if they can be used over multiple pH ranges. Quantity of indicator in aqueous (aq.) or alcohol (alc.) solution is specified. Tried-and-true indicators include: thymol blue, tropeolin OO, methyl yellow, methyl orange, bromphenol blue, bromcresol green, methyl red, bromthymol blue, phenol red, neutral red, phenolphthalein, thymolphthalein, alizarin yellow, tropeolin O, nitramine, and trinitrobenzoic acid. Data in this table are for sodium salts of thymol blue, bromphenol blue, tetrabromphenol blue, bromcresol green, methyl red, bromthymol blue, phenol red, and cresol red.

Using Procedure:

Acids
0 – Hydrochloric Acid (HCl)
1.0 – Battery Acid (H2SO4 sulfuric acid)
2.0 – Lemon Juice
2.2 – Vinegar
3.0 – Apples
4.0 – Wine and Beer
4.5 – Tomatoes
6.6 – Milk

Neutral
7.0 – Pure Water

Bases
7.4 – Human Blood
8.3 – Baking Soda (Sodium Bicarbonate)
10.5 – Milk of Magnesia
11.0 – Ammonia
12.4 – Lime (Calcium Hydroxide)
13.0 – Lye
14.0 – Sodium Hydroxide (NaOH

Note:

General  Acid-Base Indicators

 

Indicator pH Range Quantity per 10 ml Acid Base
Thymol Blue 1.2-2.8 1-2 drops 0.1% soln. in aq. red yellow
Pentamethoxy red 1.2-2.3 1 drop 0.1% soln. in 70% alc. red-violet colorless
Tropeolin OO 1.3-3.2 1 drop 1% aq. soln. red yellow
2,4-Dinitrophenol 2.4-4.0 1-2 drops 0.1% soln. in 50% alc. colorless yellow
Methyl yellow 2.9-4.0 1 drop 0.1% soln. in 90% alc. red yellow
Methyl orange 3.1-4.4 1 drop 0.1% aq. soln. red orange
Bromphenol blue 3.0-4.6 1 drop 0.1% aq. soln. yellow blue-violet
Tetrabromphenol blue 3.0-4.6 1 drop 0.1% aq. soln. yellow blue
Alizarin sodium sulfonate 3.7-5.2 1 drop 0.1% aq. soln. yellow violet
%u03B1-Naphthyl red 3.7-5.0 1 drop 0.1% soln. in 70% alc. red yellow
p-Ethoxychrysoidine 3.5-5.5 1 drop 0.1% aq. soln. red yellow
Bromcresol green 4.0-5.6 1 drop 0.1% aq. soln. yellow blue
Methyl red 4.4-6.2 1 drop 0.1% aq. soln. red yellow
Bromcresol purple 5.2-6.8 1 drop 0.1% aq. soln. yellow purple
Chlorphenol red 5.4-6.8 1 drop 0.1% aq. soln. yellow red
Bromphenol blue 6.2-7.6 1 drop 0.1% aq. soln. yellow blue
p-Nitrophenol 5.0-7.0 1-5 drops 0.1% aq. soln. colorless yellow
Azolitmin 5.0-8.0 5 drops 0.5% aq. soln. red blue
Phenol red 6.4-8.0 1 drop 0.1% aq. soln. yellow red
Neutral red 6.8-8.0 1 drop 0.1% soln. in 70% alc. red yellow
Rosolic acid 6.8-8.0 1 drop 0.1% soln. in 90% alc. yellow red
Cresol red 7.2-8.8 1 drop 0.1% aq. soln. yellow red
%u03B1-Naphtholphthalein 7.3-8.7 1-5 drops 0.1% soln. in 70% alc. rose green
Tropeolin OOO 7.6-8.9 1 drop 0.1% aq. soln. yellow rose-red
Thymol blue 8.0-9.6 1-5 drops 0.1% aq. soln. yellow blue
Phenolphthalein 8.0-10.0 1-5 drops 0.1% soln. in 70% alc. colorless red
%u03B1-Naphtholbenzein 9.0-11.0 1-5 drops 0.1% soln. in 90% alc. yellow blue
Thymolphthalein 9.4-10.6 1 drop 0.1% soln. in 90% alc. colorless blue
Nile blue 10.1-11.1 1 drop 0.1% aq. soln. blue red
Alizarin yellow 10.0-12.0 1 drop 0.1% aq. soln. yellow lilac
Salicyl yellow 10.0-12.0 1-5 drops 0.1% soln. in 90% alc. yellow orange-brown
Diazo violet 10.1-12.0 1 drop 0.1% aq. soln. yellow violet
Tropeolin O 11.0-13.0 1 drop 0.1% aq. soln. yellow orange-brown
Nitramine 11.0-13.0 1-2 drops 0.1% soln in 70% alc. colorless orange-brown
Poirrier's blue 11.0-13.0 1 drop 0.1% aq. soln. blue violet-pink
Trinitrobenzoic acid 12.0-13.4 1 drop 0.1% aq. soln. colorless orange-red

Note: This article uses material from the http://rxmarine.com/