COD Reagent Composition for High-Chloride Water Measurement
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Solution Overview
Problem
Existing methods for measuring chemical oxygen demand (COD) in high-chloride water samples require sample dilution due to interference from chlorides, limiting their applicability to concentrations above 1,000 mg/L.
Innovation Solution
A reagent set comprising mercuric sulfate (HgSO4), potassium dichromate (K2Cr2O7), and potassium aluminum sulfate (KAl(SO4)2·12H2O) in acidic solutions, which eliminate chloride interference and enable direct COD measurement in liquid media up to 20,000 mg/L without dilution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mercuric sulfate is added to eliminate chloride interference, then measurement precision is improved, but device complexity increases due to additional reagents and procedures
Solution Approach 1:
The patent introduces mercuric sulfate as an intermediary substance that mediates between the chloride ions and the potassium dichromate oxidant. The mercuric sulfate forms stable complexes with chloride ions, preventing them from interfering with the oxidation reaction. This intermediary approach resolves the contradiction by adding a controlled chemical agent that specifically addresses the interference problem without fundamentally changing the measurement system's complexity.
Solution Approach 2:
The patent modifies the chemical parameters of the measurement system by introducing mercuric sulfate and adjusting reagent compositions. This parameter change enables the system to handle high chloride concentrations (up to 20,000 mg/L) that would otherwise be impossible to measure accurately. The parameter modification resolves the contradiction by changing the chemical environment to be tolerant of chloride interference while maintaining measurement precision.
2Measurement precision
If sample dilution is performed to reduce chloride concentration, then measurement precision is improved, but productivity decreases due to additional preparation steps
Solution Approach 1:
The patent enables the measurement system to serve itself by incorporating mercuric sulfate directly into the reagent system. This self-service approach allows the system to automatically handle high chloride concentrations without requiring external intervention for sample dilution. The mercuric sulfate in the reagents automatically neutralizes chloride interference, eliminating the need for separate dilution steps and thus maintaining productivity while ensuring measurement precision.
Solution Approach 2:
The patent applies preliminary action by pre-mixing mercuric sulfate with the potassium dichromate reagent before the measurement process begins. This preliminary preparation ensures that the chloride interference is already neutralized when the sample is introduced, eliminating the need for post-sampling dilution steps. This approach resolves the contradiction by performing the interference elimination action in advance, thereby maintaining both precision and productivity.
3Adaptability or versatility
If the measurement system is designed for high-chloride samples, then adaptability is improved, but manufacturing precision becomes more difficult due to reagent stability requirements
Solution Approach 1:
The patent creates a composite reagent system that combines potassium dichromate, mercuric sulfate, and sulfuric acid in specific proportions. This composite formulation integrates multiple functional components: potassium dichromate for oxidation, mercuric sulfate for chloride complexation, and sulfuric acid for maintaining acidic conditions. The composite material approach resolves the contradiction by creating a stable, multi-component reagent that can handle a wide chloride concentration range (0-30,000 mg/L) while maintaining manufacturing consistency through defined composition ratios.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate COD measurement in high-chloride water samples without dilution, applicable to a wide chloride concentration range from 0 to 30,000 mg/L, including high concentrations where traditional methods fail.
Implementation Method 1
chloride ions can combine with mercuric sulfate to form soluble chloromercuric complexes
Implementation Method 2
when a liquid medium sample (such as a water sample) is oxidized by potassium dichromate (K2Cr2O7) under specific conditions
Implementation Method 3
using silver sulfate (Ag2SO4) as a catalyst in a strong acidic medium
Implementation Method 4
using 1,10-phenanathroline monohydrate as an indicator and ammonium ferrous sulfate ([(NH4)2Fe(SO4)2·6H2O]) to titrate the unreduced potassium dichromate in the water sample
Data Source
AI summary
The present disclosure relates to a reagent set for measuring a chemical oxygen demand in a liquid medium, the reagent set including a first reagent, wherein the first reagent is an acidic solution of mercuric sulfate; a second reagent, wherein the second reagent is an acidic solution comprising potassium dichromate; and a third reagent, wherein the third reagent is an acidic solution, characterized in that at least the second reagent or at least the third reagent further includes potassium aluminum sulfate.