Monitoring molecular diffusion of sucrose in xanthan solutions using ultrasonic velocity measurements

Measurements of the velocity of ultrasound through a sample as a function o f diffusion distance were used to study molecular diffusion of sugars throu gh biopolymer solutions, A 1. wt% xanthan solution was prepared which consi sted of a lower layer containing no sucrose, and an upper layer containing sucrose (10, 20, 30, or 40 wt%), The Velocity of ultrasound through the bio polymer solutions was measured as a function of sample height and time, and then converted into sucrose concentration-distance profiles using an empir ical calibration curve. The translational diffusion coefficient of the sucr ose in the upper and lower layers was determined by fitting the experimenta l data to a Fickian diffusion model:The measured diffusion coefficients wer e in reasonable agreement with published values for sucrose in aqueous solu tions in the absence of xanthan, which suggests the biopolymer had little i nfluence on molecular diffusion.