Triple Point Cells
Triple point cells are used in the calibration of thermometers. For exacting work, triple point cells are typically filled with a highly pure chemical substance such as hydrogen, argon, mercury, or water (depending on the desired temperature). The purity of these substances can be such that only one part in a million is a contaminant; what is called "six-nines" because it is 99.9999% pure. When it is a water-based cell, a special isotopic composition called VSMOW is used because it is very pure and produces temperatures that are more comparable from lab to lab. Triple point cells are so effective at achieving highly precise, reproducible temperatures, an international calibration standard for thermometers called ITS–90 relies upon triple point cells of hydrogen, neon, oxygen, argon, mercury, and water for delineating six of its defined temperature points.
Read more about this topic: Triple Point
Famous quotes containing the words triple, point and/or cells:
“And we fairies, that do run
By the triple Hecate’s team
From the presence of the sun,
Following darkness like a dream,
Now are frolic. Not a mouse
Shall disturb this hallowed house.”
—William Shakespeare (1564–1616)
“There’s a point of poverty at which the spirit isn’t with the body all the time. It finds the body really too unbearable. So it’s almost as if you were talking to the soul itself. And a soul’s not properly responsible.”
—Louis-Ferdinand Céline (1894–1961)
“They are sworn enemies of lyric poetry.
In prison they accompany the jailer,
Enter cells to hear confessions.
Their short-end comes down
When you least expect it.”
—Charles Simic (b. 1938)