Jackson Turbidimeter

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The Jackson Turbidimeter, also known as the Jackson Candle Turbidimeter, is 

a historic and relatively simple device used to measure high levels of turbidity in water. It works by observing how deeply a candle flame's image can be seen through a column of the water sample. This method, primarily used for coarse turbidity, has largely been replaced by more modern and precise electronic turbidimeters. 

Components

The Jackson Turbidimeter consists of four main parts: 

• Standard candle: A light source made of beeswax or paraffin wax.
• Glass turbidity tube: A flat-bottomed, calibrated glass tube that holds the water sample.
• Cylindrical metal container/stand: A support structure that houses the glass tube and holds the candle in a fixed position, 76 mm below the bottom of the tube.
• Candle holder with spring: A mechanism to keep the candle at a constant height during the test. 

Operating principle

The principle is based on light absorption and scattering. 

• The water sample is poured into the glass tube, and the image of the candle flame is viewed from the top.
• As the water level rises, the suspended particles in the water cause the light to scatter and absorb, making the flame's image appear more diffused.
• The measurement is taken when the individual candle flame disappears and is replaced by a uniform glow.
• The height of the water column at which the flame disappears is inversely proportional to the water's turbidity. The greater the water depth required to obscure the flame, the lower the turbidity.
• This depth is then converted into Jackson Turbidity Units (JTU) using a graduated scale. 

How to use

1. Preparation: Light the standard candle and place it in its holder at the base of the instrument. Conduct the test in a darkened room or with a shield to block outside light.
2. Add sample: Pour the thoroughly mixed water sample into the glass tube.
3. Observe: Look down through the water column from the top of the tube.
4. Stop: Continue pouring the sample until the image of the candle flame is no longer distinguishable.
5. Record reading: Read the turbidity directly from the graduated scale on the side of the glass tube at the height of the water level. 

Range and limitations

• High turbidity range: The Jackson turbidimeter is designed for measuring high turbidity, typically in the range of 25 to 1000 JTU. For turbidities exceeding 1000 JTU, the sample must be diluted first.
• Not for low turbidity: It is not suitable for measuring low turbidity, such as in treated drinking water, because low turbidity requires a very long water column to obscure the flame.
• Manual and subjective: The measurement depends on the observer's eyesight and the consistency of the candle flame, introducing a degree of subjectivity and variability.
• Interference: Results can be affected by color in the water, air bubbles, and rapidly settling coarse debris.
• Outdated: Because of its limitations, the Jackson method has been largely replaced by electronic nephelometers, which measure scattered light at a 90-degree angle for more precise and reliable results, especially for low-turbidity samples.

**Turbidity with a Jackson Turbidimeter** refers to a traditional method used to **measure the turbidity **cloudiness or haziness of water** by observing the visibility of a candle flame through a column of water.

### 📏 **Jackson Turbidimeter Method (Jackson Candle Turbidimeter)** **Principle:** * Based on **visual extinction** of light. * A candle is placed beneath a clear, vertical glass tube. * The water sample is poured into the tube until the flame is no longer visible from the top. * The **height of the water column** is noted. * Turbidity is expressed in **Jackson Turbidity Units JTU**. ### 💡 **Key Features:** * **Measurement unit**: Jackson Turbidity Units JTU * **Accuracy range**: Suitable for turbidity levels **less than 25 JTU** * **Used for**: Relatively high turbidity samples ***e.g., river water, wastewater*** ### 🛠️ **Limitations:** * Not suitable for **low turbidit(less than 25 JTU** * **Subjective** – relies on human vision * **Obsolete** – modern instruments like **Nephelometers** NTU-based are more accurate ### ✅ **Still Useful For:** * Educational demonstrations * Field assessments where electronic meters aren’t available