Abstract
The main factors that influence the value of surface tension of a liquid measured with the Maximum Pressure Bubble Method are critically evaluated. We present experimental results showing the effect of capillary diameter, capillary depth, bubble spheroidicity and liquid density at room temperature. We show that the decrease of bubble spheroidicity due to increase of capillary immersion depth is not sufficient to explain the deviations found in the measured surface tension values. Thus, we propose a simple experimental procedure that allows determining the surface tension of a liquid without any previous knowledge of its density. This procedure is especially useful when the liquid of interest exhibits variations of surface tension and density with time, as for example during condensation reactions to obtain SiO2 sols from a tetraethyl ortosilicate (TEOS) solutions during their aging process.
Highlights
Where dV is the change in the volume of the bubble, dA the surface area change and ΔP the pressure difference between both sides of the interface around the bubble
In the case of a bubble forming at the end of a capillary immersed in the sample liquid, by replacing in Equation 1 the geometrical characteristics of a sphere, one can arrive to Equation 2 g= R × ∆P
I: surface tension obtained by maximum pressure bubble method (MPBM) with β correction factor
Summary
This method has been known for more than 160 years. We took the dimensions of the revolution ellipsoid (“a” and “c” Figure 2b) and the pressure difference ΔP from a video recorded at the moment when the bubble detaches from the capillary
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