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PHENOL RED

MacsChem > Biological Stains > PHENOL RED

What is Phenol Red?

Phenol red, also known as phenolsulfonphthalein (PSP), is a pH indicator often used in cell biology and laboratories. It is a stable red crystal, which acts as a weak acid with a pKa of 8.00 at 20°C. In solution, phenol red switches from yellow to red as the pH shifts from 6.8 to 8.2, turning bright pink at higher pH levels. Its structure exhibits a zwitterion form under very acidic conditions. Further, it has similarities with other pH indicators like bromothymol blue and phenolphthalein.

Phenol Red Structure

CAS No.: 143-74-8

Synonyms: Phenolsulfonphthalein; Fenolipuna; Sulfonphthal; Sulphental; Sulphonthal; Phenolsulphonphthalein; Phenolred

Properties of Phenol Red

Physical Properties
Chemical formula C19H14O5S
IUPAC Name4-[3-(4-hydroxyphenyl)-1,1-dioxo-2,1λ6-benzoxathiol-3-yl]phenol
Molecular weight354.38 g/mol
SolubilitySoluble in Water, Alcohol, Aq. alkali hydroxides and Carbonates
Flash point294.2±30.1 °C
Density1.5±0.1 g/cm³
Chemical Properties
ColourDark Red to Dark Brown
StateSolid powder
Melting point>300°C
Vapour Pressure 0.0±1.6 mmHg at 25°C
pHBelow 6.8(Yellow)
6.8–8.2(Red)
Above 8.2(Bright pink or fuchsia)
LogP3.02

Uses of Phenol Red

  • pH Indicator: Phenol red is generally used in labs to monitor pH changes, mostly in cell culture media, where it specifies the health and status of growing cells.
  • Phenol Red Test (Phenolsulfonphthalein test): This test was formulated by Leonard Rowntree and John Geraghty in 1911 to analyze kidney function. Since Phenol red is eliminated through urine, it quantifies kidney functions by tracking its excretion calorimetrically.
  • Cell Culture Monitoring: It helps detect contamination or cellular waste by changing color, indicating when media needs replacing.
  • Estrogen Mimic: It acts as a weak estrogen mimic, determining cell growth in cultures that exhibit estrogen receptors.
  • Phenol Red Broth test: This test examines if bacteria can ferment a specific carbohydrate. If fermentation occurs, the broth turns yellow due to acid production. If not, it stays red or turns pink, indicating no acid formation.
  • Phenol red thread test: This thread test is a simple diagnostic tool that measures tear production in the eyes. A thread treated with phenol red is placed in the lower eyelid, and the length of the wetted portion indicates tear production levels.
  • Swimming Pool Test Kits: Phenol red is widely used as a pH indicator in pools for water testing to ensure safe water conditions.
  •  
Pictograms :  
Hazard Statements :

H315: Causes skin irritation.

H335: May cause respiratory irritation.

Precautionary statements :

P261: Avoid breathing dust.
P264: Wash skin thoroughly after handling.
P271: Use only outdoors or in a well-ventilated area.
P280: Wear protective gloves.
P302 + P352: IF ON SKIN: Wash with plenty of water.
P304 + P340 + P312: IF INHALED: Remove person to fresh air and keep comfortable for breathing. Call a POISON CENTER/ doctor if you feel unwell.

P352: Wash with plenty of water.

What is Phenol Red?

Phenol red, also known as phenolsulfonphthalein (PSP), is a pH indicator often used in cell biology and laboratories. It is a stable red crystal, which acts as a weak acid with a pKa of 8.00 at 20°C. In solution, phenol red switches from yellow to red as the pH shifts from 6.8 to 8.2, turning bright pink at higher pH levels. Its structure exhibits a zwitterion form under very acidic conditions. Further, it has similarities with other pH indicators like bromothymol blue and phenolphthalein.

Phenol Red Structure

CAS No.: 143-74-8

Synonyms: Phenolsulfonphthalein; Fenolipuna; Sulfonphthal; Sulphental; Sulphonthal; Phenolsulphonphthalein; Phenolred

Properties of Phenol Red

Physical Properties
Chemical formula C19H14O5S
IUPAC Name4-[3-(4-hydroxyphenyl)-1,1-dioxo-2,1λ6-benzoxathiol-3-yl]phenol
Molecular weight354.38 g/mol
SolubilitySoluble in Water, Alcohol, Aq. alkali hydroxides and Carbonates
Flash point294.2±30.1 °C
Density1.5±0.1 g/cm³
Chemical Properties
ColourDark Red to Dark Brown
StateSolid powder
Melting point>300°C
Vapour Pressure 0.0±1.6 mmHg at 25°C
pHBelow 6.8(Yellow)
6.8–8.2(Red)
Above 8.2(Bright pink or fuchsia)
LogP3.02

Uses of Phenol Red

  • pH Indicator: Phenol red is generally used in labs to monitor pH changes, mostly in cell culture media, where it specifies the health and status of growing cells.
  • Phenol Red Test (Phenolsulfonphthalein test): This test was formulated by Leonard Rowntree and John Geraghty in 1911 to analyze kidney function. Since Phenol red is eliminated through urine, it quantifies kidney functions by tracking its excretion calorimetrically.
  • Cell Culture Monitoring: It helps detect contamination or cellular waste by changing color, indicating when media needs replacing.
  • Estrogen Mimic: It acts as a weak estrogen mimic, determining cell growth in cultures that exhibit estrogen receptors.
  • Phenol Red Broth test: This test examines if bacteria can ferment a specific carbohydrate. If fermentation occurs, the broth turns yellow due to acid production. If not, it stays red or turns pink, indicating no acid formation.
  • Phenol red thread test: This thread test is a simple diagnostic tool that measures tear production in the eyes. A thread treated with phenol red is placed in the lower eyelid, and the length of the wetted portion indicates tear production levels.
  • Swimming Pool Test Kits: Phenol red is widely used as a pH indicator in pools for water testing to ensure safe water conditions.
  •  
Pictograms :  
Hazard Statements :

H315: Causes skin irritation.

H335: May cause respiratory irritation.

Precautionary statements :

P261: Avoid breathing dust.
P264: Wash skin thoroughly after handling.
P271: Use only outdoors or in a well-ventilated area.
P280: Wear protective gloves.
P302 + P352: IF ON SKIN: Wash with plenty of water.
P304 + P340 + P312: IF INHALED: Remove person to fresh air and keep comfortable for breathing. Call a POISON CENTER/ doctor if you feel unwell.

P352: Wash with plenty of water.

FAQs

Phenol Red is a pH indicator that is used in laboratory applications. It appears red in neutral to alkaline solutions and turns yellow in acidic conditions.

Positive phenol red indicates a pH change in a solution, typically signifying an alkaline condition. In tests, it is used to show that the environment is more basic, with phenol red turning red or pink.

Phenol red changes color because it loses protons as pH increases. It changes from yellow at pH below 6.6 to red between pH 6.6 and 8.0 and turns bright pink (fuchsia) above pH 8.1.

A phenol red test indicates the pH level of a solution. It changes color in response to pH changes, helping to distinguish if a solution is acidic, neutral, or basic.

Phenol red tablets are used to test the presence of a certain medium or to monitor pH levels in various solutions. They help in assessing the acidity or alkalinity of a sample.

A Phenol Red broth should typically be incubated and observed within 24 to 48 hours for accurate results.

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