Triple Point of Water Realization Technique | Fluke Video

In this video, Matt Newman from Fluke Calibration demonstrates the proper technique for realizing a triple point of water cell for temperature calibration.
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Transcript

Hi, my name is Matt I'm with Fluke Corporation and we're coming to you today from American Fork Utah at the heart scientific division of Fluke.

I work in the primary standards lab where among other things we make the triple point of water cell that I'll be showing you today.

Triple point of water cells is used in labs throughout the world to calibrate and maintain precision thermometers. When properly prepared, this cell will provide a reference temperature for you of exactly zero point zero one zero degrees Celsius I'm calling it: ‘a triple point of water’.

What we're seeing right now is water as a liquid and water as a gas or a vapor obviously to make a triple point. We'll have to introduce the third phase of water solid, so we'll do that by freezing an ice. In front of me I have a bowl of ground-up dry ice or frozen carbon dioxide. I have a spoon to scoop it with, I have a wire long enough to go into the well of the cell and stand there.

I have a bottle of alcohol; we're going to put four drops of alcohol into the well of the cell. Let’s try to fill it to the top, dry ice will spill that's okay. It evaporates into gas and won't leave a mess in your lab. Now I'm starting to see forming what's called an ice bridge.

I've got solid ice freezing from the well right to the outsides when that begins to happen you need to warm it up and melt it away, if you let it go one of the most commonly asked questions is how to know what I've finished or how thick does that ice mantle have to be before I can use it the scientists I work for.

I like to throw out the number eight millimeters, we want your ice mat to bel be eight millimeters thick. Well, I haven't figured out a way to open that up and measure it with a with a pair of calipers.

The ice mantle that we're seeing in there looks larger than it is as I sit here and look at it, it looks to me to be just a couple of millimeters away from the edges of the cell down. Here, I can remove the parallax, I can remove the optical distortion by setting this in a beaker full of water.

Everything is magnified but it's magnified equally now, and we can see there's still quite a gap between the ice mantle and the sides of the cell.

To summarize we started off with a pre-chilled cell, we put four drops of alcohol in the well to act as a thermal catalyst and start the freezing. We tried to keep a full well of dry ice in an attempt to have a uniformly shaped ice metal when ice bridges began to freeze, we melded them with our hands to prevent breakage.