IndicatorpH

RangeQuantity per 10

mlAcid Base

Thymol Blue 1.2-2.81-2 drops 0.1% soln. in aq.

red yellow

Pentamethoxy red 1.2-2.31 drop 0.1% soln. in 70% alc.

red-violetcolorless

Tropeolin OO 1.3-3.2 1 drop 1% aq. soln. red yellow

2,4-Dinitrophenol 2.4-4.01-2 drops 0.1% soln. in 50% alc.

colorless yellow

Methyl yellow 2.9-4.01 drop 0.1% soln. in 90% alc.

red yellow

Methyl orange 3.1-4.41 drop 0.1% aq. soln.

red orange

Bromphenol blue 3.0-4.61 drop 0.1% aq. soln.

yellow blue-violet

Tetrabromphenol blue

3.0-4.61 drop 0.1% aq. soln.

yellow blue

Alizarin sodium sulfonate

3.7-5.21 drop 0.1% aq. soln.

yellow violet

-Naphthyl red 3.7-5.01 drop 0.1% soln. in 70% alc.

red yellow

p-Ethoxychrysoidine 3.5-5.51 drop 0.1% aq. soln.

red yellow

Bromcresol green 4.0-5.61 drop 0.1% aq. soln.

yellow blue

Methyl red 4.4-6.21 drop 0.1% aq. soln.

red yellow

Bromcresol purple 5.2-6.81 drop 0.1% aq. soln.

yellow purple

Chlorphenol red 5.4-6.81 drop 0.1% aq. soln.

yellow red

Bromphenol blue 6.2-7.61 drop 0.1% aq. soln.

yellow blue

p-Nitrophenol 5.0-7.01-5 drops 0.1% aq. soln.

colorless yellow

Azolitmin 5.0-8.05 drops 0.5% aq. soln.

red blue

Phenol red 6.4-8.01 drop 0.1% aq. soln.

yellow red

Neutral red 6.8-8.01 drop 0.1% soln. in 70% alc.

red yellow

Rosolic acid 6.8-8.01 drop 0.1% soln. in 90% alc.

yellow red

Cresol red 7.2-8.81 drop 0.1% aq. soln.

yellow red

-Naphtholphthalein 7.3-8.71-5 drops 0.1% soln. in 70% alc.

rose green

Tropeolin OOO 7.6-8.91 drop 0.1% aq. soln.

yellow rose-red

Thymol blue 8.0-9.61-5 drops 0.1% aq. soln.

yellow blue

Phenolphthalein 8.0-10.01-5 drops 0.1% soln. in 70% alc.

colorless red

-Naphtholbenzein 9.0-11.01-5 drops 0.1% soln. in 90% alc.

yellow blue

Thymolphthalein 9.4-10.61 drop 0.1% soln. in 90% alc.

colorless blue

Nile blue10.1-11.1

1 drop 0.1% aq. soln.

blue red

Alizarin yellow10.0-12.0

1 drop 0.1% aq. soln.

yellow lilac

Salicyl yellow10.0-12.0

1-5 drops 0.1% soln. in 90% alc.

yelloworange-brown

Diazo violet10.1-12.0

1 drop 0.1% aq. soln.

yellow violet

Tropeolin O11.0-13.0

1 drop 0.1% aq. soln.

yelloworange-brown

Nitramine11.0-13.0

1-2 drops 0.1% soln in 70% alc.

colorlessorange-brown

Poirrier's blue11.0-13.0

1 drop 0.1% aq. soln.

blue violet-pink

Trinitrobenzoic acid12.0-13.4

1 drop 0.1% aq. soln.

colorless orange-red

Indicator Color at low Transition pH Color at high

pH

pHrange

(approximate)

Methyl violet yellow 0.0-1.6 blue-violet

Malachite green yellow 0.2-1.8 blue-green

Thymol blue (acid - first transition) red 1.2-2.8 yellow

Methyl yellow (in ethanol) red 2.9-4.0 yellow

Bromophenol blue yellow 3.0-4.6 violet

Congo red blue 3.0-5.2 red

Methyl orange red 3.1-4.4 yellow

Methyl orange in xylene cyanole solution

purple 3.2-4.2 green

Bromocresol green yellow 3.8-5.4 blue

Methyl red red 4.2-6.3 yellow

Litmus (Azolitmin) red 4.5-8.3 blue

Bromocresol purple yellow 5.2-6.8 violet

Bromothymol blue yellow 6.0-7.6 blue

Phenol red yellow 6.6-8.0 red

Neutral Red red 6.8-8.0 yellow

Thymol blue (base - second transition)

yellow 8.0-9.6 blue

Phenolphthalein colorless 8.2-10.0 pink

Thymolphthalein colorless 9.4-10.6 blue

Alizarin Yellow R yellow 10.1-12.0 orange-red

Indigo carmine blue 11.4-13.0 yellow

Acid-Base IndicatorsHow do acid-base indicators work?Frequently asked questions about indicators

alizarin red S

Approximate pH range for color change: 4.6-6.0Color of acid form: yellowColor of base form: red

alizarin yellow GG

Type: In + H2O InH+ + OH-

pK: 11.0Approximate pH range for color change: 10.0-12.0Color of acid form: clearColor of base form: yellow

alizarin yellow R

Also known as: sodium 5-(p-nitrophenylazo)benzenesulfonateApproximate pH range for color change: 10.1-12.0Color of acid form: yellowColor of base form: red

brilliant yellow

Approximate pH range for color change: 6.6-7.8Color of acid form: yellowColor of base form: orange

bromocresol green

Also known as: 3',3'',5',5''-tetrabromo-m-cresol-sulfonephthalein

Type: HIn + H2O In- + H3O+

pK: 4.90Approximate pH range for color change: 3.8-5.4

Color of acid form: yellowColor of base form: blue

bromophenol blue

Also known as: 3',3'',5',5''-tetrabromophenolsulfonephthalein

Type: HIn + H2O In- + H3O+

pK: 4.10Approximate pH range for color change: 3.0-4.6Color of acid form: yellowColor of base form: purple

bromothymol blue

Also known as: 3',3''-dibromothymolsulfonephtalein

Type: HIn + H2O In- + H3O+

pK: 7.30Approximate pH range for color change: 6.0-7.6Color of acid form: yellowColor of base form: blue

chlorophenol red

Also known as: 3',3''-dichlorophenolsulfonephthalein

Type: HIn + H2O In- + H3O+

pK: 6.25Approximate pH range for color change: 4.8-6.4Color of acid form: yellowColor of base form: red

clayton yellow

Approximate pH range for color change: 12.2-13.2Color of acid form: yellowColor of base form: amber

congo red

Approximate pH range for color change: 3.0-5.0Color of acid form: blueColor of base form: red

cresol red (in acid solution)

Also known as: o-cresolsulfonephthaleinApproximate pH range for color change: 0.0-1.0Color of acid form: redColor of base form: yellow

cresol red (in basic solution)

Also known as: o-cresolsulfonephthaleinApproximate pH range for color change: 7.0-8.8Color of acid form: yellowColor of base form: red

crystal violet

Type: HIn + H2O In- + H3O+

pK: -Approximate pH range for color change: 0.0-1.8Color of acid form: yellowColor of base form: blue

dimethyl yellow

Type: In + H2O InH+ + OH-

pK: 3.25

Approximate pH range for color change: 2.9-4.0Color of acid form: redColor of base form: yellow

erythrosine (sodium salt)

Approximate pH range for color change: 2.2-3.6Color of acid form: orangeColor of base form: red

malachite green

pK: 1.0Approximate pH range for color change: 0.2-1.8Color of acid form: yellowColor of base form: blue-green

metacresol purple (in acid solution)

Also known as: m-cresol purple, cresol purple, m-cresolsulfonephthaleinpK: ~2.0Approximate pH range for color change: 1.2-2.8Color of acid form: redColor of base form: yellow

metacresol purple (in basic solution)

Also known as: m-cresol purple, cresol purple, m-cresolsulfonephthalein

Type: HIn + H2O In- + H3O+

pK: 8.32Approximate pH range for color change: 7.6-9.2Color of acid form: yellowColor of base form: purple-red

metanil yellow

Also known as: m-(p-anilinophenylazo)benzene sulfonateApproximate pH range for color change: 1.2-2.4Color of acid form: redColor of base form: yellow

methyl green

Approximate pH range for color change: 0.2-1.8Color of acid form: yellowColor of base form: blue

methyl orange

Type: InH+ + H2O In + H3O+

pK: 3.46Approximate pH range for color change: 3.1-4.4Color of acid form: redColor of base form: orange-yellow

methyl red

Type: InH+ + H2O In + H3O+

pK: 5.00Approximate pH range for color change: 4.4-6.2Color of acid form: redColor of base form: yellow

neutral red

Approximate pH range for color change: 6.8-8.0Color of acid form: redColor of base form: amber

phenolphthalein

Type: HIn + H2O In- + H3O+

pK: 9.5Approximate pH range for color change: 8.0-9.8Color of acid form: clearColor of base form: red-violet

phenol red

Also known as: phenolsulfonephthalein

Type: HIn + H2O In- + H3O+

pK: 8.00Approximate pH range for color change: 6.4-8.2Color of acid form: yellowColor of base form: red

paramethyl red

Also known as: sodium p-(p-dimethylaminophenylazo)-benzoateApproximate pH range for color change: 1.0-3.0Color of acid form: redColor of base form: yellow

paranitrophenol

Also known as: p-nitrophenol

Type: HIn + H2O In- + H3O+

pK: 7.15Approximate pH range for color change: 5.6-7.6Color of acid form: colorlessColor of base form: yellow

quinaldine red

Approximate pH range for color change: 1.0-2.2Color of acid form: clearColor of base form: red

resazurin

Approximate pH range for color change: 3.8-6.4Color of acid form: orangeColor of base form: violet

thymolphthalein

Type: HIn + H2O In- + H3O+

pK: 9.7Approximate pH range for color change: 9.3-10.5Color of acid form: colorlessColor of base form: blue

thymol blue (in acid solution)

Also known as: thymolsulfonephthalein

Type: HIn + H2O In- + H3O+

pK: 1.65Approximate pH range for color change: 1.2-2.8Color of acid form: redColor of base form: yellow

thymol blue (in basic solution)

Also known as: thymolsulfonephthalein

Type: HIn + H2O In- + H3O+

pK: 9.20Approximate pH range for color change: 8.0-9.6Color of acid form: yellowColor of base form: blue

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 waterEthyl violet 0.0 2.4 yellow blue 0.1% in 50%

methanol/waterMalachite green 0.2 1.8 yellow blue-

greenwater

Methyl green 0.2 1.8 yellow blue 0.1% in water2-(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 ethanolParamethyl Red (p-(p-dimethylaminophenylazo)-benzoic acid, sodium salt)

1.0 3.0 red yellow ethanol

Metanil Yellow 1.2 2.4 red yellow 0.01% in water4-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 7.4 9.0 yellow purple 0.04% in 0.01048

(m-cresolsulfonephthalein) M NaOHOrange 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 waterErythrosine, disodium salt 2.2 3.6 orange red 0.1% in waterBenzopurpurine 48 2.2 4.2 violet red 0.1% in waterN,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

NaOH2,4-dinitrophenol 2.8 4.0 colourless yellow saturated in waterN,N-dimethyl-p-phenylazoaniline 2.8 4.4 red yellow 0.1% in 90%

ethanol/waterCongo red 3.0 5.0 blue red 0.1% in waterMethyl orange-xylene cyanole solution

3.2 4.2 purple green ready solution

Methyl orange 3.2 4.4 red yellow 0.01% in waterEthyl orange 3.4 4.8 red yellow 0.05-0.2% in

water4-(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 water4-phenylazo-1-naphthylamine 4.0 5.6 red yellow 0.1% in ethanol2-(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 ethanolAlizarin red S 4.6 6.0 yellow red dilute in waterMethyl red 4.8 6.0 red yellow 0.02% in 60%

ethanol/waterPropyl red 4.8 6.6 red yellow ethanolBromocresol 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 waterAlizarin 5.6 7.2 yellow red 0.1% in methanolAlizarin 11.0 12.4 red purple 0.1% in methanol2-(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 yellowBrilliant yellow 6.6 7.8 yellow orange 1% in waterPhenol red 6.6 8.0 yellow red 0.04% in 0.01128

(phenolsulfonephthalein) M NaOHNeutral red 6.8 8.0 red amb 0.01% in 50%

ethanol/waterm-nitrophenol 6.8 8.6 colourless yellow 0.3% in waterCresol 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 ethanolCurcumin 10.2 11.8     ethanolMetacresol 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 ethanolp-naphtholbenzene 8.2 10.0 orange blue 1% in dilute alkaliPhenolphthalein 8.2 10.0 colourless pink 0.05% in 50%

ethanol/waterEthyl-bis(2,4-dimethylphenyl)acetate

8.4 9.6 colourless blue saturated solution in 50%

acetone/ethanolThymolphthalein 9.4 10.6 colourless blue 0.04% in 50%

ethanol/waterAlizarin yellow R (5-(p-nitrophenylazo)salicylic acid,

10.1 12.0 yellow red 0.01% in water

sodium salt)p-(2,4-dihydroxyphenylazo)benzenesulfonic 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