Development of measuring diffusion coefficients by digital holographic interferometry in transparent liquid mixtures

Area of Science:

• Physical Chemistry
• Optical Measurement Techniques

Background:

• Measuring diffusion coefficients in transparent liquids is crucial for understanding mass transport phenomena.
• Existing methods using digital holographic interferometry have limitations in accuracy and convenience.
• Mach-Zehnder interferometry offers a simpler approach but can be improved.

Purpose of the Study:

• To enhance the accuracy and convenience of diffusion coefficient measurement in transparent liquids.
• To refine existing digital holographic interferometry techniques by integrating established analysis procedures.
• To introduce a novel approach for determining the initial time in diffusion experiments.

Main Methods:

• Combined hologram analysis procedures from Mialdun et al. (2011) and He et al. (2009).
• Utilized polynomial fitting for continuous phase difference to accurately determine peak distances in concentration profiles.
• Developed minimization functions to precisely determine the initial time shift in diffusion experiments.

Main Results:

• Successfully measured the diffusion coefficient of KCl in water at 0.33 mol/L and 25 °C.
• Obtained a diffusion coefficient value of 1.844 × 10⁻⁹ m²/s with a low uncertainty of ± 0.012 × 10⁻⁹ m²/s.
• Achieved a relative uncertainty of less than 1% for the diffusion coefficient and a temperature uncertainty within ± 0.04 K.

Conclusions:

• The refined digital holographic interferometry method provides accurate and convenient diffusion coefficient measurements.
• The integration of specific analysis techniques and initial time determination improves upon previous methods.
• Results align well with other established measurement techniques, validating the enhanced approach.