• Based on a 24-bit high-resolution A/D converter
• Automatic sampling analysis and auto-calibration
• Measuring cycle time adjustable
• Wet chemistry analysis with Potassium Dichromate Reflux method
• Quantitative syringe system for precise dosing
• Sampling valve can resist high temperature, corrosion, acid, and alkaline
• Self-diagnosis & friendly calibration setting
• User-friendly graphical interface
• Highly stable and accurate with a wide measuring range
• 7” LCD color touch panel display
• Reagents free and cost-saving
• Simultaneously display parameters of Ammonia and analysis cycle time
• Language support in English and Chinese
• Automatic data storage with capacity up to 5000 historical records. (User could expend memory by using 32GB/64GB flash disk.)
• The automatic alarm of a shortage of liquid chemical replenishment dosing

Oxygen is important essential in environment. If water contains a great amount of organic matter which consumes excessive oxygen, it can lead to anaerobic conditions, which is deleterious to higher aquatic life forms. Because the environmental conscious is rising, in various industries raised the standards as well as governmental regulations. Chemical Oxygen Demand is an important water quality parameter and it provides an index to monitor the contamination in the water. W3111 COD on-line analyzer can measure water quality accurately to ensure the water quality safety. In water emission monitoring, discharge points could be located in suburban or places where can’t conduct continuous sample analysis. On-line analyzer can provide a solution and REAL-TIME monitor water quality. There are several methods to monitor the consuming oxygen in water, such as biochemical oxygen demand (BOD), Chemical Oxygen Demand (COD) and Total Oxygen Demand (TOD). COD contrasts with biochemical oxygen demand (BOD), which BOD test takes five days to complete, COD test take within 2hours or less to complete. COD with Potassium Dichromate Reflux method is more time-efficient and popular as a standard recognized by most governments in the world. W3111 COD on-line analyzer is automatic and reliable analyzer which can save time and staffs as well as dosing accurately to save cost.

The principle of Chemmit W3111 COD analyzer is following US’ EPA 410.4 method and APHA Standard Method 5220D. It adopts Potassium Dichromate Reflux method to proceed continuous monitoring. When the sample transported into overflow cup, a certain volume sample is mixed with a dichromate reagent solution and sulfuric acid. The solution is refluxed at 150℃for a fixed period of time and then determines the consumption of dichromate by colorimeter. Reagents also contain silver sulfate as an oxidation catalyst and mercuric sulfate for the purpose to complex chloride ions in sample. Two simplified chemical equations to illustrate the reactions are:
C_aH_bO_c + Cr₂O₇^2- + H⁺　→→→　 Cr³⁺ + CO₂ + H₂O
Organics Cr⁶⁺ Acid →→→　Cr³⁺ + CO₂ + H₂O
The COD value is determined by innovated LED emitter colorimetric detection.