Chemistry

pH Indicators

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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

Categories: Chemistry