Preparation of Acid-Base Indicators

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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