Talk:Vienna Standard Mean Ocean Water

message: Braindrain0000: I like the revisions you made to the second–to–last paragraph of the VSMOW in temperature measurement section. They make for more fluid reading.
There were several technicalities that weren’t correct or were misleading when the last paragraph of VSMOW in temperature measurement said “The differences between water’s classical melting and boiling points and those of calibrated VSMOW water have little practical meaning in real life, as environmental factors may alter these values by a greater amount. For example, an altitude change of only 28 cm (11 inches) causes water’s boiling point to change by a millikelvin.” (Go to current paragraph.)
:1: Calibrated VSMOW water is an unusual term.  VSMOW water automatically refers to water of certain isotopic composition.,
:2: “Environment factors” is plural.  However, there is only one environmental factor that influences the boiling point of water: pressure.
:3: The temperature coefficient of water’s ice point looks like a brick wall when the phase/temperature graph is scaled to visualize the boiling point.  Huge pressure changes are required in order to observe pressure’s effect on the freezing point.  Accordingly, the paragraph was revised to focus correctly on the only technical issue at play: pressure's effect on water's boiling point.
:4: This revision also helps to avoid implying that the 16.1 mK difference is due to standardizing on a particular isotopic composition.  VSMOW water is simply a definition intended to produce an “average” ocean water.  Even if someone used water made from melted snow to delineate the triple point in a particular experiment, the error would only be a fraction of one millikelvin.  The entire 16.1 mK difference is due to the current values chosen to define absolute zero and the triple point for the Kelvin and Celsius scales.
In order to make 0 °C and 100 °C once again be the melting and boiling points of water (VSMOW water to be precise), absolute zero would have to be re-defined as -273.1940 °C, and the triple point would have to be defined as 0.0104 °C (as opposed to the current values of –2373.15 and 0.01).   Greg L 21:56, 17 September 2006 (UTC)
replies: text: While I know that pressure is the only technical factor on water, I was referring more to the layman's definition of "environmental factors," which would include the physical conditions that influence pressure. --Carl (talk|contribs) 23:39, 17 September 2006 (UTC)
thread_title: Freezing Point

message: I'd imagine, given the use in high accuracy measurements, that VSMOW is (supposed to be) pure H2O, without any dissolved materials in it. I bring this up, because the incorporation of "ocean water" in the name. The first thought that comes into my mind when people are making an ocean water/non-ocean water distinction is the presence of salt. It took me a while to come to the understanding that the "ocean water" distinction is referring to the fact that isotope ratios are different in ocean water that's been purified, versus rainwater that's been purified. -- 19:22, 1 December 2006 (UTC)
thread_title:  No Salt, Right? 

message: Excerpt from actual article:
However, current measurements show that the triple and melting points of VSMOW water are only 0.009 911(10) °C apart. Thus, the actual melting point of ice is +0.000 089(10) °C.
Thanks
Confusedreader (talk) 17:13, 22 January 2008 (UTC)
replies: text: It is a shorthand for 0.009 911 ± 0.000 010 °C. See Uncertainty#Measures. --62.224.94.221 (talk) 02:36, 20 March 2008 (UTC)
thread_title:  What does "(10)" at the end of the values for the difference between the triple point of VSMOW and the melting point of ice, and the actual melting point of ice mean? 

message: What was the reason that the triple point was chosen to define the Kelvin rather than freezing point at standard pressure?  Is it that the triple point is easier to define or what? XinaNicole (talk) 01:38, 19 October 2012 (UTC)
replies: text: It is because the triple point is a propery of water only.   The freezing point requires an arbitrary standard pressure. Palter5 (talk) 18:01, 21 January 2015 (UTC)
replies: text: That is not quite true.  Other materials also exhibit a triple point.  For example hydrogen has a triple point of 13.8033 K.  Using the freezing point is problematic because the freezing point of water varies with applied presure (recall that the pressure applied by the weight of a skater on ice is enough to lower the freezing point of the ice immediately under the skate).  The triple point is a fixed point for any given material.  For a material to exist as a solid, liquid and gas at the same time occurs only at one specific temperature and one specific pressure.  For water this occurs at a temperature of 273.16 K (by definition) and a partial pressure of 611.73 pascals.  The term 'partial pressure' means that the gas part of the water may contain other gases and the resultant pressure be correspondingly higher.  It is only the component part of the pressure exerted by the gaseous water that counts.  86.149.139.90 (talk) 15:10, 6 September 2015 (UTC)
thread_title:  Why Triple Point? 

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