Is 3-point of H20 used for Kelvin a certain set of isotope

In summary, the conversation discusses the definition of the unit of Kelvin and whether it is defined as water with specific isotopes such as 2 Hydrogen-1 & 1 Oxygen-16. It is questioned whether using different isotopes would introduce an error that affects the desired accuracy, and it is mentioned that water outside of Earth may have a different isotope occurrence. The conversation also mentions the term "Vienna Standard Mean Ocean Water," which is a gaiocentric presumption. The participants then discuss why this presumption may be problematic, especially since the Kelvin is about to be redefined.
  • #1
swampwiz
571
83
If I had had enough space to enter the proper question, it would have been:

Is the triple point of water which is used for the definition of the unit of Kelvin defined as water having a certain isotopes such as 2 Hydrogen-1 & 1 Oxygen-16?

Or would the error introduced by using different isotopes not make a difference up to the level of desired accuracy - or is there a defined occurrence of the various isotopes? It seems that the water that exists outside of the Earth could have a different isotope occurrence, and therefore presuming that water everywhere in the Universe has the same occurrence of the isotopes as on Earth would be a gaiocentric presumption.
 
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  • #2
Google "Vienna Water."
 
  • #3
Actually "Vienna Standard Mean Ocean Water". Searching for "Vienna Water" brings up the water works for Vienna, VA, LOL.

https://en.wikipedia.org/wiki/Vienna_Standard_Mean_Ocean_Water

So the definition does use a gaiocentric presumption. I suppose that it has to be this way.
 
  • #4
swampwiz said:
nd therefore presuming that water everywhere in the Universe has the same occurrence of the isotopes as on Earth would be a gaiocentric presumption.

Why is this bad? (Especially as the Kelvin is about to be redefined)
 

1. What is the 3-point of H20 used for Kelvin?

The 3-point of H20 refers to the triple point of water, which is the temperature and pressure at which water can exist in all three phases (solid, liquid, and gas) in equilibrium. It is used as a reference point for the Kelvin scale, which is a temperature scale based on absolute zero and is commonly used in scientific research.

2. Is the use of 3-point of H20 specific to a certain set of isotopes?

No, the use of 3-point of H20 is not specific to a certain set of isotopes. The triple point of water remains constant regardless of the isotopes present in the water molecules. However, the values for the triple point may vary slightly depending on the isotopic composition of the water.

3. How is the triple point of water determined?

The triple point of water is determined experimentally by measuring the temperature and pressure at which the three phases of water (solid, liquid, and gas) are in equilibrium. This is usually done using a specialized apparatus called a triple point cell.

4. Why is the triple point of water important for the Kelvin scale?

The triple point of water is important for the Kelvin scale because it provides a fixed reference point for defining the temperature scale. Since the triple point of water is a unique and reproducible state for water, it allows for accurate and precise measurements of temperature.

5. Can the triple point of water change?

The triple point of water is a well-defined state for water and is not expected to change. However, slight variations in the isotopic composition or impurities in the water can cause small changes in the values for the triple point. Therefore, it is important to use highly pure water and standardized methods when determining the triple point of water.

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