椭圆法测量接触角

接触角在胶体与表面化学,矿物浮选，洗涤和油气开采等领域是一项重要的物性参数。接触角的测量方法很多，其中固滴法因只需少量试样，简便易行而应用较广。人们为避免人为因素对固滴法中作切线的影响，在此基础上提出了各种通过测量液滴尺寸计算接触角的间接方法，并以圆法，即半角法应用最广。这些方法将液滴剖面视为圆形，液滴剖面受重力影响偏离圆形，使计算结果产生误差，在液滴体积较大和界面张力较低时尤为明显。Ryley建议将油滴剖面视为椭圆，在其轮廓线上选择三点，测量六个数据计算接触角，该法不受重力影响，较圆法优越，缺点是需要测量的数据较多，计算公式复杂，难以推广应用。本文提出只需在椭圆轮廓线上选择两点，测量四个数据计算接触角的方法，计算公式比较简单，便于推广应用。

Measurement of the Contact Angle by Ellipse Method

ABSTRACT: Contact Angle is an important physical parameter in colloid and Surface Chemistry, mineral flotation, washing and oil and gas production. There are many methods to measure the contact angle, among which the sessile drop method is widely used because only a few samples are needed. In order to avoid the influence of human factors on tangent in solid drop method, various indirect methods for calculating the contact angle by measuring the droplet size are proposed, and the circular method, i. e. the half angle method, is most widely used. In these methods, the drop profile is regarded as a circle, and the drop profile deviates from the circle under the influence of gravity, which leads to errors in the calculation, especially when the volume of the drop is large and the interfacial tension is low. In this paper, a new method for calculating the contact angle is presented, which regards the oil drop profile as an ellipse. The calculated results are not affected by the droplet volume and interfacial tension, and are more accurate than the classical circle method, and simpler calculation formula especially suitable for low oil-water interfacial tension due to surfactant in water. Compared with Ryleyes ellipse method, this method has less measurement data.