I am regularly startled by little things that trigger new understanding about our slice of the instrument World. This time it is about surface tension.
As you know, if you’re involved with the phenomenon of surface tension, the most common unit of measure is the dyne/centimeter. This represents the force needed to overcome the energy that keeps the surface of a liquid from flying into the air.
The tensiometer is an accepted device for making surface tension measurements. These range from simple mechanical instruments to complex automatic electronic tensiometers. Since we manufacture and distribute tensiometers, we are regularly asked questions about the phenomenon of surface tension, how to measure it in different liquids, range of readings to expect for a material, how the instrument works and other questions about these analyzes.
Historically, tensiometers have had scales in the range of 0 to 100 dynes/centimeter. Over many years of working with tensiometer users, I never speculated about the reasons for or appropriateness of this measurement range.
Recently we’ve been asked, several times;”How do you measure surface tension above 100 dynes/centimeter?” These inquiries provoked us to investigate the reasons behind the question. Our inquires soon lead us to examine another proposition; “Why would you want to measure more than 100 dynes/centimeter?”
In our research about high levels of surface tension, we found to our surprise that water, ranging from 72 at room temperature to just above 75 at near boiling, had the highest surface tension of all but one other material. The exception is Mercury which has a surface tension of about 500 dynes/centimeter at room temperature. The other exceptions are molten metals but at very high temperatures.
Our findings clearly show that what may look like an arbitrary scale on simple mechanical and as well as on complex automatic tensiometers, represents appropriate ranges for an overwhelming majority of materials,
Thus, with water at the top in the 70’s and the low end at less than one, the answer is that this range is more than enough to meet the needs of industry for a wide span of surface tension measurement.
As an aside, we did not find an application that required a surface tension measurement of Mercury.
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Wonder what will astound me next.
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