A practical device for surface tension measurement in volatile fluids

A surface tension analyzer specially designed to handle volatile fluids suc h as refrigerant 134a (R-134a) has been designed and constructed. Surface t ension is greatly affected by temperature and the contaminants in the liqui d. A relatively simple and practical method was developed to measure the su rface tension of a small sample of volatile liquid, and to determine whethe r it had become contaminated with dissolved oil, grease or a surface active agent. The maximum bubble pressure method was selected and the apparatus c onstructed was tested using distilled water and methanol. The experimental difficulties overcome in the design and the operation of the device are dis cussed and sample measurements for water, methanol, and R-134a are presente d. The device works well with volatile fluids and the uncertainty of the me asurements is less than +/-2%.