The "Shanghai Yetuo COD Reflux Digestion Device" is a type of equipment used for detecting chemical oxygen demand (COD) in water quality based on the potassium dichromate method. Its core function is to achieve standardized reflux digestion of COD in water samples, and it is a key instrument in water quality analysis laboratories.

1、 Core concept breakdown

To understand this device, two basic prerequisites need to be clarified first:

1. COD (Chemical Oxygen Demand): An indicator that measures the content of reducing substances (mainly organic matter) in water bodies. The higher the value, the more severe the water is polluted by organic matter. It is a core parameter for evaluating the degree of water pollution and the effectiveness of sewage treatment.

2. Reflux digestion: The core step of the potassium dichromate method for detecting COD is to use potassium dichromate as an oxidant and silver sulfate as a catalyst in a strong acid environment (sulfuric acid) to oxidize and decompose organic matter in the water sample. At the same time, a reflux device is used to prevent the loss of volatile substances during the reaction process, ensuring that the oxidation reaction is complete. Finally, the COD value is calculated by titration or photometry.

Shanghai Yetuo "is usually an equipment brand (such as Shanghai Yetuo Instrument Technology, etc.). This type of equipment is essentially a standardized instrument that integrates" reflux "and" digestion "functions, replacing the traditional manual operation of" electric furnace+glass reflux device "to improve detection efficiency and accuracy.

2、 Working principle (potassium dichromate method)

The core logic of the equipment follows the national standard potassium dichromate method, and the process can be divided into three steps:

1. Sample pretreatment: Add the water sample, potassium dichromate standard solution, and silver sulfate sulfuric acid catalyst in proportion to a digestion tube.

2. Reflux digestion: The equipment uses a heating module (usually aluminum block heating or infrared heating) to stabilize the temperature of the digestion tube at 165 ℃± 2 ℃ (national standard requirement), and at the same time, uses a built-in reflux condenser tube (water-cooled) to condense and reflux volatile gases (such as SO ₂ and water vapor) generated in the reaction to the digestion tube, avoiding sample loss and ensuring that organic matter is fully oxidized (digestion time is usually 2 hours, and some rapid models can shorten it to 15-30 minutes).

3. Subsequent testing: After digestion is completed, COD can be calculated in two ways:

-Traditional titration method: Titrate the remaining potassium dichromate with ferrous ammonium sulfate and calculate COD based on consumption;

-Luminescence method: Using the linear relationship between the absorbance and COD value of trivalent chromium (Cr ³ ⁺) generated by the reduction of potassium dichromate, the results are directly read through the built-in photometric module of the instrument (some intelligent models integrate this function).

3、 Core structure and functional characteristics

1. Core structure

The structure of the Yetuo COD reflux digestion device is designed around "high efficiency reflux+precise temperature control", mainly including:

Structural module: Heating module

Function: Provides stable heat source (temperature control accuracy ± 1 ℃), mostly designed for multi-channel (such as 6/8/12 channels), can process multiple samples simultaneously

Structural module: Reflux condensation system

Function: Built in glass condenser tube (or quartz condenser tube), externally connected to tap water/circulating water machine, to achieve condensation and reflux of volatile substances

Structural module: Temperature control system

Function: Using PID temperature control technology to monitor and adjust temperature in real time, avoiding reagent decomposition or result deviation caused by overheating

Structural module: an fully protected module

Function: Overheating protection, anti dry burning protection, condensate water cut-off alarm (some models), reducing operational risks

Structural module: Sample rack/digestion tube

Function: Use a digestion tube (nai high temperature, anti-corrosion) with a fixed frame to ensure stable heating of the sample

2. Functional features (compared to traditional manual devices)

Gao efficiency: Multi channel design (such as 12 channels) can process 12 samples simultaneously, and the digestion time can be accurately controlled (traditional manual monitoring requires individual monitoring);

Accuracy: PIDjing precise temperature control (± 1 ℃) avoids incomplete oxidation caused by temperature fluctuations in traditional electric furnaces, the reflux system is well sealed, and there is no sample loss;

AN integrity: Built in overheating protection, anti dry burning function, automatic alarm when condensate water is cut off, avoiding the hidden danger of "open flame+glass tube" in traditional devices;

Convenience: Some models integrate "digestion+photometric detection" without transferring samples, directly reading COD values, reducing human errors;

Compliance: Wan fully complies with the requirements of the national standard GB 11914-2024 "Determination of Chemical Oxygen Demand in Water Quality - Potassium Dichromate Method", and the data can be used for official testing reports.

4、 Applicable scenarios

The Yetuo COD reflux digestion device is mainly used in scenarios where accurate COD detection is required. Typical users include:

Environmental monitoring agency: Routine COD monitoring of surface water, groundwater, and nearshore seawater;

Wastewater treatment plant: COD detection of influent/effluent to evaluate the efficiency of wastewater treatment process;

Industrial enterprises: COD self inspection of wastewater discharge outlets in chemical, printing and dyeing, food, pharmaceutical and other industries (must comply with environmental discharge standards);

Research and Education: Water Quality Research Experiments in University Environmental Engineering Laboratories and Research Institutions.

5、 Precautions for use

1. Reagent A: During the digestion process, concentrated sulfuric acid (highly corrosive) and potassium dichromate (toxic) are used. Acid resistant gloves and goggles should be worn to avoid contact between the reagent and the skin;

2. Requirements for condensate water: It is necessary to ensure that the condensate water is continuously flowing smoothly (it is recommended to use a circulating water machine to avoid water pressure fluctuations that may cause interruption), otherwise it may cause the sample to evaporate and result in lower quality;

3. Sample pretreatment: If the water sample contains a large amount of suspended solids or chloride ions (such as seawater or high salt wastewater), it is necessary to first filter or add mercuric sulfate (to mask chloride ions) to avoid interference with the detection;

4. Regular calibration: It is recommended to calibrate the instrument with standard COD samples (such as 100mg/L and 500mg/L standard solutions) every 3-6 months to ensure detection accuracy.

In summary, the Yetuo COD reflux digestion device is a "standardized tool" for water quality COD detection. Its core value is to solve the problems of low efficiency, large errors, and poor integrity of traditional manual operations through automated and standardized design, ensuring the reliability and compliance of COD detection data