Preparation of Acid-Base
Indicators
The data on this Web page are in the public domain. Copying is encouraged.
The quantities listed in the "Preparation" column did not come down with Moses from Mount
Sinai. They ought to be considered to be only good approximations. The audience of users, the
decision whether to determine a titration error for a particular color change and the experimental
environment must be considered when deciding what quantity is best to use.
| Indicator | pH Change | Color Change | Preparation |
| Methyl Violet | 0.0 - 1.6 | yel to bl | 0.01- 0.05 % in water |
| Crystal Violet | 0.0 - 1.8 | yel to bl | 0.02% in water |
| Ethyl Violet | 0.0 - 2.4 | yel to bl | 0.1 g in 50 ml of MeOH + 50 ml of water |
| Malachite Green | 0.2 - 1.8 | yel to bl grn | water |
| Methyl Green | 0.2 - 1.8 | yel to bl | 0.1% in water |
| 2 - (p - dimethylaminophenylazo)pyridine | 0.2 - 1.8, 4.4 - 5.6 | yel to bl, red to yel | 0.1 % in ETOH |
| o - Cresolsulfonephthalein (Cresol Red) | 0.4 - 1.8, 7.0 - 8.8 | yel to red, yel to red | 0.1 g in 26.2 ml 0.01M NaOH + 223.8 ml water |
| Quinaldine Red | 1.0 - 2.2 | col to red | 1 % in ETOH |
| p - (p - dimethylaminophenylazo) - benzoic acid, Na - salt (Paramethyl Red) | 1.0 - 3.0 | red to yel | ETOH |
| m - (p - anilnophenylazo)benzene sulfonic acid, Na - salt (Metanil Yellow) | 1.2 - 2.4 | red to yel | 0.01% in water |
| 4 - Phenylazodiphenylamine | 1.2 - 2.6 | red to yel | 0.01 g in 1 ml 1M HCI + 50 ml ETOH + 49 ml water |
| Thymolsulfonephthalein (Thymol Blue) | 1.2 - 2.8, 8.0 - 9.6 | red to yel, yel to bl | 0.1 g in 21.5 ml 0.01 M NaOH + 229.5 mL water |
| m - Cresolsulfonephthalein (Metacresol Purple) | 1.2 - 2.8, 7.4 - 9.0 | red to yel, yel to purp | 0.1 g in 26.2 ml 0.01M NaOH + 223.8 ml water |
| p - (p - anilinophenylazo)benzenesulfonic acid, Na - salt (Orange IV) | 1.4 - 2.8 | red to yel | 0.01 % in water |
| 4 - o - Tolylazo - o - toluidine | 1.4 - 2.8 | or to yel | water |
| Erythrosine, disodium salt | 2.2 - 3.6 | or,to red | 0.1% in water |
| Benzopurpurine 48 | 2.2 - 4.2 | vt to red | 0. 1 170 in water |
| N,N - dimethyl - p - (m - tolylazo)aniline | 2.6 - 4.8 | red to yel | 0.1% in water |
| 4,4' - Bix(2 - amino - l - naphthylazo)2,2' - stil - benedisulfonic acid | 3.0 - 4.0 | purp to red | 0.1 g in 5.9 ml 0.05 M NaOH + 94.1 ml water |
| Tetrabromophenolphthaleinethyl ester, K - salt | 3.0 - 4.2 | yel to bl | 0.1 % in ETOH |
| 3',3",5',5" - tetrabromophenol - sulfonephthalein (Bromophenol Blue) | 3.0 - 4.6 | yel to bl | 0.1 g in 14.9 ml 0.01M NaOH + 235.1 ml water |
| 2,4 - Dinitrophenol | 2.8 - 4.0 | colorless to yel | saturated water solution |
| N,N - Dimethyl - p - phenylazoaniline (p - Dimethylaminoazobenzene) | 2.8 - 4.4 | red to yel | 0.1 g in 90 ml in ETOH + 10 ml water |
| Congo Red | 3.0 - 5.0 | blue to red | 0.1% in water |
| Methyl Orange - Xylene Cyanole solution | 3.2 - 4.2 | purp to grn | ready solution |
| Methyl Orange | 3.2 - 4.4 | red to yel | 0.01 % in water |
| Ethyl Orange | 3. 4 - 4. 8' | red to yel | 0.05 - 0.2% in water or aqueous ETOH |
| 4 - (4 - Dimethylamino - 1 - naphthylazo) - 3 - methoxybenzenesulfonic acid | 3.5 - 4.8 | vt to yel | 0.1% in 60% ETOH |
| 3',3",5',5" - Tetrabromo - m - cresol - sulfonephthalein (Bromocresol Green) | 3.8 - 5.4 | yel to blue | 0.1 g in 14.3 ml 0.01 M NaOH + 235.7 ml water |
| Resazurin | 3.8 - 6.4 | or to vt | water |
| 4 - Phenylazo - l - naphthylamine | 4.0 - 5.6 | red to yel | 0.1 % in ETOH |
| Ethyl Red | 4.0 - 5.8 | col to red | 0.1 g in 50 ml MEOH + 50 ml water |
| 2 - (p - Dimethylaminophenylazo) - pyridine | 0.2 - 1.8, 4.4 - 5.6 | yel to red, red to yel | 0.1 % in ETOH |
| 4 - (p - ethoxyphenylazo) - m - phenylene - diamine monohydrochloride | 4.4 - 5.8 | or to yel | 0.1% in water |
| Lacmoid | 4.4 - 6.2 | red to bl | 0.2% in ETOH |
| Alizarin Red S | 4.6 - 6.0 | yel to red | 0.2 g in 100 mL of 1.5% HCl |
| Methyl Red | 4.8 - 6.0 | red to yel | 0.02 g in 60 ml ETOH + 40 ml water |
| Propyl Red | 4.8 - 6.6 | red to yel | ETOH |
| 5',5" - Dibromo - o - cresolsulfone - phthalein (Bromocresol Purple) | 5.2 - 6.8 | yel to purp | 0.1 g in 18.5 ml 0.01M NaOH + 231.5 ml water |
| 3',3" - Dichlorophenolsulfonephthalein (Chlorophenol Red) | 5.2 - 6.8 | yel to red | 0.1 g in 23.6 ml 0.01 M NaOH + 226.4 ml water |
| p - Nitrophenol | 5.4 - 6.6 | col to yel | 0.1% in water |
| Alizarin | 5.6 - 7.2, 11.0 - 12.4 | yel to red, red to purp | 0.1 % in MEOH |
| 2 - (2,4 - Dinitrophenylazo) - l - naphthol - 3, 6 - disulfonic acid, di - Na salt | 6.0 - 7.0 | yel to bl | 0.1% in water |
| 3',3" - Dibromothymolsulfonephthalein (Bromothymol Blue) | 6.0 - 7.6 | yel to bl | 0.1 gin 16 ml 0.01 M NaOH + 234 ml water |
| 6,8 - Dinitro - 2,4 - (lH)quinazolinedione (m - Dinitrobenzoylene urea) | 6.4 - 8.0 | col to yel | 25 g in 115 ml M NaOH + 50 ml boiling water 0.292g of NaCl in 100 ml water |
| Brilliant Yellow | 6.6 - 7.8 | yel to or | 1 % in water |
| Phenolsulfonephthalein (Phenol Red) | 6.6 - 8.0 | yel to red | 0.1 gin 28.2 ml 0.01M NaOH + 221.8 ml water |
| Neutral Red | 6.8 - 8.0 | red to amb | 0.01 g in 50 ml ETOH + 50 ml water |
| m - Nitrophenol | 6.8 - 8.6 | col to yel | 0.3170 in water |
| o - Cresolsulfonephthalein (Cresol Red) | 0.0 - 1.0, 7.0 - 8.8 | red to yel, yel to red | 0.1 g in 26.2 ml 0.01 M NaOH + 223.8 ml water |
| Curcumin | 7.4 - 8.6, 10.2 - 11.8 | yel to red | ETOH |
| m - Cresolsulfonephthalein (Metacresol Purple) | 1.2 - 2.8, 7.4 - 9.0 | red to yel, yel to purp | 0.1 gin 26.2 ml 0.01M NaOH + 223.8 ml water |
| 4,4' - Bis(4 - amino - i - Daphthylazo) 2,2'stilbene disulfonic acid | 8.0 - 9.0 | bl to red | 0.1 gin 5.9 ml 0.05 M NaOH + 94.1 ml water |
| Thymolsulfonephthalein (Thymol Blue) | 1.2 - 2.8, 8.0 - 9.6 | red to yel | 0.1 g in 21.5 ml 0.01 M NaOH + 228.5 ml water |
| o - Cresolphthalein | 8.2 - 9.8 | col to red | 0.04% in ETOH |
| p - Naphtholbenzene | 8.2 - 10.0 | or to bl | I % in dil. alkali |
| Phenolphthalein | 8.2 - 10.0 | col to pink | 0.05 gin 50 mL ETOH + 50 mL water |
| Ethyl - bis (2.4 - dimethylphenyl)acetate | 8.4 - 9.6 | col to bl | saturated solution in 50% acetone alcohol |
| Thymolphthalein | 9.4 - 10.6 | col to bl | 0.04 g in 50 ml ETOH + 50 ml water |
| 5 - (p - Nitrophenylazo)salicylic acid, Na - salt (Alizarin Yellow R) | 10.1 - 12.0 | yel to red | 0.01 % in water |
| p - (2,4 - Dihydroxyphenylazo)benzene - sulfonic acid, Na - salt | 11.4 - 12.6 | yel to or | 0.1 % in water |
| 5,5' - Indigodisulfonic acid, di - Na - salt | 11.4 - 13.0 | bl to yel | water |
| 2,4,6 - Trinitrotoluene | 11.5 - 13.0 | co] to or | 0.1 - 0.5% in ETOH |
| 1,3,5 - Trinitrobenzene | 12.0 - 14.0 | col to or | 0.1 - 0.5% in ETOH |
| Clayton Yellow | 12.2 - 13.2 | yel to amb | 0.1% in water |