we used contact angle meter (drop shape analysis system) to measure surface tension of seawater at temp. 20℃. Seawater is from China South Sea. Surface tension of seawater is slightly higher than distilled water. The result is kept almost same as result measured by Wilhelmy Plate method from force tensiometry. And, our drop shape analysis system can   distinguish the difference and get a more suitable result. And more important function of our software is we can save fitting curve and measured result at drop image and all drop images and result will be managed by function of "report management". It is very useful when you want to check out your result after many days. visit http://www.usakino.com to find more information about our contact angle goniometer, surface tensiometer.