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CHEMISTRY
pH INDICATORS CHART
 
(Note: This is a large table so please wait for it to load. Thanks.)

Gray blocks indicate approximate pH range where the indicator is changing color.

Indicator                                      0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10. 11. 12. 13. 14. Preparation                       
Methyl Violet 0.0-1.6                                              .01-.05% in water
Crystal Violet 0.0-1.8                                              .02% in water
Ethyl Violet 0.0-2.4                                              .1g 50% methanol/water
Malachite Green 0.2-1.8                               water
Methyl Green 0.2-1.8                                   .1% in water
Cresol Red .04-1.8                                   ammonia/water
Thymol Blue 1.2-2.8                               ammonia/water
Bromophenol Blue 3.0-4.6                               ammonia/water
Congo Red 3.0-5.0                               .1% in water
Methyl Orange 3.2-4.4                               .01% in water
Resorcin Blue 4.4-6.2                               .2% ethanol
Alzarin Red S 4.6-6.0                               water
Methyl Red 4.8-6.0                               ethanol/water
Litmus 5.0-8.0                               water
Bromoceresol Purple 5.2-6.8                               ammonia/water
Chrophenol Red 5.2-6.8                               ammonia/water
Bromothymol Blue 6.0-7.6                               ammonia/water
Phenol Red 6.6-8.0                               ammonia/water
Neutral Red 6.8-8.0                               ethanol/water
Tumaric Curcumin 7.4-8.6                               ethanol
Phenolphthalein 8.2-10.0                             ethanol/water
Thymophthalein 9.4-10.6                               ethanol/water
Alzarin Yellow R 10.1-12.0                               .01% in water
Clayton Yellow 12.2-13.2                               .1% in water

The pH chart above is available HERE on a separate page for printing.

If you see a value, like pH, or pKa, then it's a log.  Otherwise it is most likely a powers of ten value.

 pH Calculator:  http://www.orpelectrode.com/Support/phcal.htm

How pH Indicators work http://www.chemguide.co.uk/physical/acidbaseeqia/indicators.html

Understanding pH: http://www.coscosci.com/lab/ph.htm

Acid Base Indicators http://www.carlton.paschools.pa.sk.ca/chemical/equilibrium/abindicators.htm

Activities in pH: http://www.iit.edu/~smile/ch9310.html


           pH Calculator:  http://www.orpelectrode.com/Support/phcal.htm


 

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
a-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
a-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
a-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

 

Primary References:
Lange's Handbook of Chemistry, 8th Edition, Handbook Publishers Inc., 1952.
Volumetric Analysis, Kolthoff & Stenge, Interscience Publishers, Inc., New York, 1942 and 1947.


MAKE YOUR OWN Ph BUFFERS  http://www.bi.umist.ac.uk/users/mjfrbn/buffers/makebuf.asp

pH Tutorial Launch Pad
Basic pH Tutorial
Acids & Bases Problem Set
pH Tutorial
Acid, Base, and pH Tutorial
pH Tutorial
Science Junction - Water What Ifs pH Tutorial
Miami Museum of Science: The pH Factor
Acids and Bases
Redox Eq Acidic/ Basic
Soil Testing
Antifreeze
Aquariums
Butter
Pool Care

If you are using an electronic pH meter here is some useful information concerning probe care and calibration.

You can make your own pH calibration/buffer solutions as follows.

For short-term storage (up to 24 hours) place the electrode in pH-4 or pH-7 buffer solution.  For long-term storage (more than 24 hours) Store the electrode in a buffer pH-4/KCl storage solution.  You can prepare a storage solution by adding 10 g of solid potassium chloride (KCl) to 100 mL of buffer pH-4 solution. By storing the electrode in this solution, the reference portion of the electrode is kept moist. Keeping the reference junction moist adds to electrode life and retains electrode response time when the unit is placed back into use.   If the electrode is inadvertently stored dry (NOT RECOMMENDED!), soak the probe in a pH-4 or pH-7 solution for a minimum of eight hours prior to service. The pH Electrode can be cleaned with a light dishwashing detergent solution. For heavy deposits the electrode may be carefully cleaned with a 0.1 molar solution of HCl for no more than 30 seconds, then washed in a light detergent solution. Immediately after cleaning, rinse the electrode in pure distilled water. If the electrode still fails to calibrate properly, or responds slowly, electrode replacement is recommended. Mold growth in the buffer/KCl storage solution can be prevented by adding a commercial growth inhibitor. This mold will not harm the electrode and can easily be removed using a light detergent solution.  Do not use the electrode in solutions containing perchlorate, silver, or sulfide ions.  Do not use it in hydrofluoric acid or in acid or base solutions with a concentration greater than 1.0 molar. The electrode may be used to measure the pH of sodium hydroxide solutions with a concentration near 1.0 molar, but should not be left in this concentration of sodium hydroxide for periods longer than 5 minutes. Using or storing the electrode at very high temperatures or very low temperatures (near 0C) can damage it beyond repair.

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Ph Tutorial with questions

Food Chart

Acid Base pH Tutorial

 


pH and TDS charts for plants grown using hydroponics

Fruit pH category cF PPM
Banana 5.5-6.5 M 18-22 1260-1540
Black Currant 6.0 L 14-18 980-1260
Blueberry 4.0 -5.0 M 18-20 1260-1400
Melon 5.5-6.0 H 20-25 1400-1750
Passionfruit 6.5 M 16-24 840-1680
Paw -Paw 6.5 H 20-24 1400-1680
Pineapple 5.5-6.0 H 20-24 1400-1680
Red Currant 6.0 M 14-18 980-1260
Rhubarb 5.0- 6.0 M 16-20 840-1400
Strawberries 6.0 M 18-22 1260-1540
Watermelon 5.8 M 15-24 1260-1680

Flowers pH category cF PPM
African Violets 6.0-7.0 L 12-15 840-1050
Anthurium 5.0-6.0 M 16.20 1120-1400
Antirrhinim 6.5 M 16-20 1120-1400
Aphelandra 5.0-6.0 M 18-24 1260-1680
Aster 6.0-6.5 M 18-24 1260-1680
Begonia 6.5 L 14-18 980-1260
Bromeliads 5.0-7.5 L 8-12 560-840
Caladium 6.0-7.5 M 16-20 1120-1400
Canna 6.0 M 18-24 1260-1680
Carnation 6.0 H 20-35 1260-2450
Chrysanthemum 6.0-6.2 H 18-25 1400-1750
Cymbidiums 5.5 L 6-10 420-560
Dahlia 6.0-7.0 M 15-20 1050-1400
Dieffenbachia 5.0 H 18-24 1400-1680
Dracaena 5.0-6.0 H 18-24 1400-1680
Ferns 6.0 M 16-20 1120-1400
Ficus 5.5-6.0 M 16-24 1120-1680
Freesia 6.5 M 10-20 700-1400
Impatiens 5.5-6.5 M 18-20 1260-1400
Gerbera 5.0-6.5 H 20-25 1400-1750
Gladiolus 5.5-6.5 H 20-24 1400-1680
Monstera 5.0-6.0 H 18-24 1400-1680
Palms 6.0-7.5 M 16-20 1120-1400
Roses 5.5-6.0 M 15-25 1050-1750
Stock 6.0-7.0 M 16-20 1120-1400

Vegetable Crops pH Category cF PPM
Artichoke 6.5-7.5 L 8-18 560-1260
Asparagus 6.0-6.8 L 14-18 980-1260
Bean (Common) 6.0 M 20-40 1400-2800
Beetroot 6.0-6.5 H 8-50 1260-3500
Broad Bean 6.0-6.5 M 18-22 1260-1540
Broccoli 6.0-6.8 H 28-35 1960-2450
Brussels Sprout 6.5 H 25-30 1750-2100
Cabbage 6.5-7.0 H 25-30 1750-2100
Capsicum 6.0-6.5 M 18-22 1260-1540
Carrots 6.3 M 16-20 1120-1400
Cauliflower 6.5-7.0 M 5-20 1050-1400
Celery 6.5 M 18-24 1260-1680
Cucumber 5.5 M 17-25 1190-1750
Eggplant 6.0 H 25-35 1750-2450
Endive 5.5 M 20-24 1400-1680
Fodder 6.0 M 18-20 1260-1400
Garlic 6.0 L 14-18 980-1260
Leek 6.5-7.0 L 14-18 980-1260
Lettuce 6.0-7.0 L 8-12 560-840
Marrow 6.0 M 18-24 1260-1680
Okra 6.5 H 20-24 1400-1680
Onions 6.0-6.7 L 14-18 980-1260
Pak-choi 7.0 M 15-20 1050-1400
Parsnip 6.0 L 14-18 980-1260
Pea 6.0-7.0 L 8-18 980-1260
Pepino 6.0-6.5 H 20-50 1400-3500
Potatoes 5.0-6.0 H 20-25 1400-1750
Pumpkin 5.5-7.5 M 18-24 1260-1680
Radish 6.0-7.0 M 16-22 840-1540
Spinach 60-7.0 M 18-23 1260-1610
Silverbeet 6.0-7.0 M 18-23 1260-1610
SweetCorn 6.0 M 16-24 840-1680
SweetPotato 5.5-6.0 H 20-25 1400-1750
Taro 5.0-5.5 H 25-30 1750-2100
Tomatoes 6.0-6.5 H 20-50 1400-3500
Turnip 6.0-6.5 M 18-24 1260-1680
Zucchini 6.0 M 18-24 1260-1680



Use of Topical Archive Multiple-Choice Questions
Teachers:

Feel free to copy and paste any of the multiple-choice questions below for use in creating your own Regents-style assessments.

Graphics are easily downloaded by right-clicking on the desired image and selecting either Save Picture As... (Internet Explorer) or Save Image As... (Netscape).


Acids, Bases, & Salts: Question 1 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

Which formula represents a salt?
  1. KOH
  2. KCl
  3. CH3OH
  4. CH3COOH

Correct Answer Number: 2

Explanation: See Ref. Table K.    CH3COOH is an organic acid, acetic acid also called ethanoic acid. Choice 1 will yield the OH- ion in solution (this compound is therefore a base, See Table L). Choice 3 is an alcohol, See Table R. Salts are ionic compounds that do not form OH- or H+ ions. KCl forms K+ and Cl- ions. Therefore it is a salt.


Acids, Bases, & Salts: Question 2 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

Which substance can be classified as an Arrhenius acid?
  1. HCL
  2. NaCl
  3. LiOH
  4. KOH

Correct Answer Number: 1

Explanation: By definition an Arrhenius acid yields hydrogen ions as the only positive ions in aqueous solution. Choice 2 is a salt. Choice 3 forms Li+ and OH- ions; choice 4 also forms OH- ions: these compounds are Arrhenius bases. Choice 1 forms H+ ions and is therefore an Arrhenius acid.


Acids, Bases, & Salts: Question 3 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

Which solution will change red litmus to blue?
  1. HCl(aq)
  2. NaCl(aq)
  3. CH3OH(aq)
  4. NaOH(aq)

Correct Answer Number: 4

Explanation: Red litmus turns blue when a base is present. Hint: blue for base. Choice 1 is an acid; choice 2 is a salt and salts neutralize acids and bases. The litmus does not change color with salts. Choice 3 is an alcohol not a base. It is not found on Ref. Table L. NaOH is a strong base and will change red litmus to blue.


Acids, Bases, & Salts: Question 4 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

An acidic solution could have a pH of
  1. 7
  2. 10
  3. 3
  4. 14

Correct Answer Number: 3

Explanation: On the pH scale, a pH of less than 7 is acidic; a pH of more than 7 is basic. A neutral solution such as pure water has a pH of 7.


Acids, Bases, & Salts: Question 5 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

What is the pH of a 0.00001 molar HCl solution?
  1. 1
  2. 9
  3. 5
  4. 4

Correct Answer Number: 3

Explanation: By definition pH is the negative log (logarithm) of the hydronium ion concentration. A 0.00001 molar solution has a H+ concentration of 10-5 M (move the decimal point 5 places to the right). The value of the negative exponent (-5) gives a pH of 5. See also #7 and #19, this topic.


Acids, Bases, & Salts: Question 6 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

What is the pH of a solution with a hydronium ion concentration of 0.01 mole per liter?
  1. 1
  2. 2
  3. 10
  4. 14

Correct Answer Number: 2

Explanation: By definition pH is the negative log (logarithm) of the hydronium ion concentration. A 0.01 molar solution has a H+ concentration of 10-2 (move the decimal point 2 places to the right). The value of the negative exponent (-2) gives a pH of 2. See also #6 and #19, this topic.


Acids, Bases, & Salts: Question 7 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

There are alternate acid base theories that define an acid as any species that can
  1. donate a proton
  2. donate an electron
  3. accept a proton
  4. accept an electron

Correct Answer Number: 1

Explanation: According to Bronsted-Lowry theory, an acid is any species that can donate a proton to another species.


Acids, Bases, & Salts: Question 8 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

Which 0.1 M solution will turn phenolphthalein pink?
  1. HBr(aq)
  2. CO2(aq)
  3. LiOH(aq)
  4. CH3OH(aq)

Correct Answer Number: 3

Explanation: Different indicators change color at differing concentrations of hydrogen ions. Phenolphthalein turns pink in basic solutions that range from about 8.2 to 10 and colorless in acid solutions.(See Table M) Since the question wants it to turn pink, you are looking for a base.
Choice 4 is an alcohol: it is neutral in water. Locate choices 1 and 2 on Ref. Table K. Note that they are acidic in water. Group 1 elements of the Periodic Table (Li, Na and K) form strong bases when combined with hydroxide (OH)-. When dissolved in water, LiOH makes a strongly basic solution.(Table L) It will turn phenolphthalein pink.


Acids, Bases, & Salts: Question 9 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

Given the equation: H+ + OH- <-> H2O
Which type of reaction does the equation represent?
  1. esterification
  2. decomposition
  3. hydrolysis
  4. neutralization

Correct Answer Number: 4

Explanation: By definition neutralization occurs when equal quantities of an acid (H+) react with equal quantities of a base (OH-) to form water.


Acids, Bases, & Salts: Question 10 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

When HCl(aq) is exactly neutralized by NaOH(aq), the hydrogen ion concentration in the resulting mixture is
  1. always less than the concentration of the hydroxide ions
  2. always greater than the concentration of the hydroxide ions
  3. always equal than the concentration of the hydroxide ions
  4. sometimes greater and sometimes less than the concentration of the hydroxide ions

Correct Answer Number: 3

Explanation: Answer 4 is impossible. Neutralization means equivalent amounts of hydronium and hydroxide ions react in solution to produce water. Water has a pH of 7. By definition, only answer 3 is correct.


Acids, Bases, & Salts: Question 11 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

As the hydrogen ion concentration of an aqueous solution increases, the hydroxide ion concentration of this solution will
  1. decrease
  2. increase
  3. remain the same

Correct Answer Number: 1

Explanation: (OH-) multiplied by (H3O+) is a constant number equal to 1 x 10-14 for aqueous solutions. In other words, (A) (B) = -14. Substituting numbers, (-7) (2) = -14.
But if 7 is increased to 14, 2 must decrease to -1 to keep the answer -14. (14) (-1) =-14.
If (H3O+) increases, (OH-) must decrease.


Acids, Bases, & Salts: Question 12 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

A student wishes to prepare approximately 100 milliliters of an aqueous solution of 6M HCl using 12 M HCl. Which procedure is correct?
  1. adding 50 mL of 12 M HCl to 50 mL of water while stirring the mixture steadily.
  2. adding 50 mL of 12 M HCl to 50 mL of water and then stirring the mixture steadily.
  3. adding 50 mL of water to 50 mL of 12 M HCl while stirring the mixture steadily.
  4. adding 50 mL of water to 50 mL of 12 M HCl and then stirring the mixture steadily.

Correct Answer Number: 1

Explanation: Safety Rule: always add acid to water; This prevents the acid from splattering. Never add water to acid. Place a glass stirring rod in the water and slowly pour the acid along the rod. Some concentrated acids like HCl have an exothermic reaction in water, releasing a large amount of heat and causing the water-acid solution to boil. Constant stirring diffuses the acid throughout the solution, helping to evenly distribute the generated heat.


Acids, Bases, & Salts: Question 13 of 13
This question may require the use of the Chemistry Reference Tables or the Periodic Table of Elements.

The following data were collected at the endpoint of a titration performed to find the molarity of an HCl solution.

Volume of acid (HCl) used = 14.4 mL
Volume of base (NaOH) used = 22.4 mL
Molarity of standard base (NaOH) = 0.20 M

What is the molarity of the acid solution?
  1. 1.6 M
  2. 0.64 M
  3. 0.31M
  4. 0.13M

Correct Answer Number: 3

Explanation: Using the titration method, the volume of acid x the molarity of the acid neutralizes an equal volume of base x the molarity of the base. Or
VAcid x MAcid = VBase x MBase where V = volume and M = molarity of HCl and NaOH.
You are looking for the molarity of HCL or
(14.4 mL) (M of HCl) = (22.4 mL) ( 0.20M).
Rearranging terms, M of NaOH = (22.4 mL) (0.20 M) / 14.4 mL = 0.31 M.
See #12 , Acids and Bases. See also Reference Table T for formulas.

Acid Base Indicators

Indicator

pH Range

Colour Change

Preparation

Methyl violet

0.0

1.0

yellow

blue

0.01-0.05% in water

Crystal violet

0.0

1.8

yellow

blue

0.02% in water

Ethyl violet

0.0

2.4

yellow

blue

0.1% in 50% methanol/water

Malachite green
0.2
1.8
yellow
blue-green
water
Methyl green

0.2

1.8

yellow

blue

0.1% in water

2-(p-dimethylaminophenylazo)pyridine

0.2

1.8

yellow

blue
0.1% in ethanol
2-(p-dimethylaminophenylazo)pyridine

4.4

5.6

red

yellow
0.1% in ethanol
Cresol Red (o-cresolsulfonephthalein)

0.4

1.8

yellow

red

0.1% in 0.001048 M NaOH(aq)

Cresol Red (o-cresolsulfonephthalein)

7.0

8.8

yellow

red

0.1% in 0.001048 M NaOH(aq)

Quinaldine Red

1.0

2.2

colourless

red

1% in ethanol

Paramethyl Red (p-(p-dimethyl
aminophenylazo)-benzoic acid, sodium salt)

1.0

3.0

red

yellow

ethanol

Metanil Yellow

1.2

2.4

red

yellow

0.01% in water

4-phenylazodiphenylamine

1.2

2.6

red

yellow

0.01% in 0.01 M HCl in 50%ethanol/water

Thymol blue (thymolsulfonephthalein)

1.2

2.8

red

yellow

0.04% in 0.0086 M NaOH

Thymol blue (thymolsulfonephthalein)

8.0

9.6

yellow

blue

0.04% in 0.0086 M NaOH

Metacresol purple
(m-cresolsulfonephthalein)

1.2

2.8

red

yellow

0.04% in 0.01048 M NaOH

Metacresol purple
(m-cresolsulfonephthalein)

7.4

9.0

yellow

purple

0.04% in 0.01048 M NaOH

Orange IV (p-(p-anilinophenylazo)
benzenesulfonic acid, sodium salt)

1.4

2.8

red

yellow

0.01% in water

4-o-tolylazo-o-toluidine

1.4

2.8

orange

yellow

water

Erythrosine, disodium salt

2.2

3.6

orange

red

0.1% in water

Benzopurpurine 48

2.2

4.2

violet

red

0.1% in water

N,N-dimethyl-p-(m-tolylazo)aniline

2.6

4.8

red

yellow

0.1% in water

4,4'-bis(2-amino-1-naphthylazo)2,2'-
stilbenedisulfonic acid

3.0

4.0

purple

red

0.1% in 0.00295 M NaOH

Tetrabromophenolphthaleinethyl ester,
potassium salt

3.0

4.2

yellow

blue

0.1% in ethanol

Bromophenol blue
(3',3",5',5"-tetrabromophenolsulfonephthalein)

3.0

4.6

yellow

blue

0.04% in 0.000596 M NaOH

2,4-dinitrophenol

2.8

4.0

colourless

yellow

saturated in water

N,N-dimethyl-p-phenylazoaniline

2.8

4.4

red

yellow

0.1% in 90% ethanol/water

Congo red

3.0

5.0

blue

red

0.1% in water

Methyl orange-xylene cyanole solution

3.2

4.2

purple

green

ready solution

Methyl orange

3.2

4.4

red

yellow

0.01% in water

Ethyl orange

3.4

4.8

red

yellow

0.05-0.2% in water

4-(4-dimethylamino-1-naphthylazo)-3-
methoxybenzenesulfonic acid

3.5

4.8

violet

yellow

0.1% in 60% ethanol

Bromocresol green (3',3",5',5"-tetrabromo-m-
cresolsulfonephthalein)

3.8

5.4

yellow

blue

0.04% in 0.00572 M NaOH

Resazurin

3.8

6.4

orange

violet

water

4-phenylazo-1-naphthylamine

4.0

5.6

red

yellow

0.1% in ethanol

2-(p-dimethylaminophenylazo)-pyridine

0.2

1.8

yellow

red

0.1% in ethanol

2-(p-dimethylaminophenylazo)-pyridine

4.4

5.6

red

yellow

0.1% in ethanol

4-(p-ethoxyphenylazo)-m-phenylenediamine
monohydrochloride

4.4

5.8

orange

yellow

0.1% in water

Lacmoid

4.4

6.2

red

blue

0.2% in ethanol

Alizarin red S

4.6

6.0

yellow

red

dilute in water

Methyl red

4.8

6.0

red

yellow

0.02% in 60% ethanol/water

Propyl red

4.8

6.6

red

yellow

ethanol

Bromocresol purple
(5',5"-dibromo-o-cresolsulfone-phthalein)

5.2

6.8

yellow

purple

0.04% in 0.0074 M NaOH

Chlorophenol red
(3',3"-dichlorophenolsulfonephthalein)

5.2

6.8

yellow

red

0.04% in 0.00944 M NaOH

p-nitrophenol

5.4

6.6

colourless

yellow

0.1% in water

Alizarin

5.6

7.2

yellow

red

0.1% in methanol

Alizarin

11.0

12.4

red

purple

0.1% in methanol

2-(2,4-dinitrophenylazo)-1-naphthol-3,6-
disulfonic acid, disodium salt

6.0

7.0

yellow

blue

0.1% in water

Bromothymol blue
(3',3"-dibromothymolsulfonephthalein)

6.0

7.6

yellow

blue

0.04% in 0.0064 M NaOH

m-dinitrobenzoylene urea

6.4

8.0

colourless

yellow
 
Brilliant yellow

6.6

7.8

yellow

orange

1% in water

Phenol red (phenolsulfonephthalein)

6.6

8.0

yellow

red

0.04% in 0.01128 M NaOH

Neutral red

6.8

8.0

red

amb

0.01% in 50% ethanol/water

m-nitrophenol

6.8

8.6

colourless

yellow

0.3% in water

Cresol red (o-cresolsulfonephthalein)

0.0

1.0

red

yellow

0.04% in 0.01048 M NaOH

Cresol red (o-cresolsulfonephthalein)

7.0

8.8

yellow

red

0.04% in 0.01048 M NaOH

Curcumin

7.4

8.6

yellow

red

ethanol

Curcumin

10.2

11.8

 

 

ethanol

Metacresol purple
(m-cresolsulfonephthalein)

1.2

2.8

red

yellow

0.04% in 0.01048 M NaOH

Metacresol purple
(m-cresolsulfonephthalein)

7.4

9.0

yellow

purple

0.04% in 0.01048 M NaOH

4,4'-bis(4-amino-1-naphthylazo)-2,2'-
stilbene disulfonic acid

8.0

9.0

blue

red

0.1% in 0.00295 M NaOH

Thymol blue
(thymolsulfonephthalein)
1.2
2.8
red
yellow
0.04% in 0.0086 M NaOH
Thymol blue
(thymolsulfonephthalein)
8.0
9.6
   
0.04% in 0.0086 M NaOH
o-cresolphthalein

8.2

9.8

colourless

red

0.04% in ethanol

p-naphtholbenzene

8.2

10.0

orange

blue

1% in dilute alkali

Phenolphthalein

8.2

10.0

colourless

pink

0.05% in 50% ethanol/water

Ethyl-bis(2,4-dimethylphenyl)acetate

8.4

9.6

colourless

blue

saturated solution in 50% acetone/ethanol

Thymolphthalein

9.4

10.6

colourless

blue

0.04% in 50% ethanol/water

Alizarin yellow R (5-(p-
nitrophenylazo)salicylic acid, sodium salt)

10.1

12.0

yellow

red

0.01% in water

p-(2,4-dihydroxyphenylazo)benzene
sulfonic acid, sodium salt)

11.4

12.6

yellow

orange

0.1% in water

5,5'-indigosulfonic acid, disodium salt

11.4

13.0

blue

yellow

water

2,4,6-trinitrotoluene

11.5

13.0

colourless

orange

0.1-0.5% in ethanol

1,3,5-trinitrobenzene

12.0

14.0

colourless

orange

0.1-0.5% in ethanol

Clayton yellow

12.2

13.2

yellow

amb

0.1% in water

 

 


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