Talk:Torr

message: 199.168.7.243 20:42, 13 August 2007 (UTC)
thread_title:  temperature and pressure 

message: Can we stick to either Engineering Notation or normalized Scientific Notation (or even plain decimal)?
For example in the conversion table, in the atm column, it has 1.0197×10−5 in one row and 70.307×10−3 in another.  It seems like consistently using normalized Scientific Notation (i.e., changing the latter to 7.0307×10−2) would make it a lot easier to get a quick sense of the different magnitudes.Erikmartin (talk) 18:28, 22 October 2008 (UTC)
thread_title: Numeric Notation

message: I eliminated this: 
'The Torr' is also the name given to a Bristol based rock band which formed in 1998 and are still performing and recording today. Noteable members include: Jon Steadman, Neil Berry & James Trotham.
If it is found useful, it should be put in a stub page or in a disambiguation page. SaintCahier 17:00, 6 August 2007 (UTC)
thread_title: Band?

message: Is there an official torr now defined in terms of another measurement system, or do you measure your own?
:This is close to 1 mmHg at 0 °C and standard gravity.  That is the temperature that was most often used for metric units based on a column of mercury; for inches of mercury, in earlier times 60 °F was more common but the ones still in use today are most often exactly equal to 24.4 mmHg, so are also essentially equivalent to the 32 °F (0 °C) variety, though mercury is no longer actually used in the precise definitions.
:It's just that defining a standard atmosphere as both 101.325 kPa and 760 mmHg makes a more precise definition of these units based on the units for which standards are currently maintained, namely the SI units.  That 101.325 kPa number was chosen because it was, to the nearest pascal, the calculated pressure of 760 mm mercury at a certain conventional density under those conditions.  Gene Nygaard 22:22, 20 Dec 2004 (UTC)
replies: text: — Gene Nygaard 23:41, 24 Jan 2005 (UTC)

text: Most relevant to this discussion is that we at Wikipedia have our own "house rules"— and one of them is that you do not arbitrarily mess with an article's consistent use of a particular spelling of litre/liter, color/colour, tyre/tire, and the like.  Gene Nygaard 23:50, 24 Jan 2005 (UTC)

text: Another point:  There are lots of Canadian Tire stores, and not one Canadian Tyre store.  We also spell this word tire in the United States, so this is an international English spelling.  Yet there are Wikipedia articles which spell this word tyre. International does not mean prescriptive for the whole English-speaking world. Gene Nygaard 00:55, 25 Jan 2005 (UTC)
thread_title: More importantly, 1mmHG at Earth's gravity 

message: The following table of conversion factors appears in many Wikipedia articles:
The table was removed from the present article because it flatly contradicts the article itself.  The table says that 1 Torr = 1 mmHg.  One of the main points of the article is that 1 Torr is not equal to1 mmHg. While it is true that 1 Torr almost equals 1 mmHg, the two units are not identical.  
Among the many articles in Wikipedia that deal with pressure, some contain copies of this table while others do not.  An example of the former is Pressure.  An example of the latter is  Conversion of units.  Since the table is, at best, misleading (and frankly wrong from a technical viewpoint), I think it should be entirely removed from Wikipedia (not just from the present article).  Also, as a matter of principle, “millimeter of mercury” and “mmHg” should not be redirected to Torr.
:The table you pasted here says that 1 torr ≈ 1 mm Hg; that's "approximately equal".  Maybe your browser doesn't support unicode properly? --Slashme 09:16, 28 October 2007 (UTC)
replies: text: It should be "equals".  See the section above this.  Just like feet or meters or whatever, these units have had various definitions over time.  That's all that is involved here.  -- Gene Nygaard (talk) 17:16, 16 November 2007 (UTC)
thread_title: Conversion tables

message: The SI unit of pressure is the pascal (Pa).  Other units in common use are derived from SI units according to the following four definitions (see article for references):
	
*   The atmosphere (symbol: atm) is defined as exactly 101,325 Pa. 
*   The bar (symbol: bar) is defined as exactly 100,000 Pa. 
*    The torr (symbol: Torr) is defined as exactly 1/760 atm.
*    The millimeter of mercury (symbol: mmHg) is defined as the product of (1) the “standard’ density of mercury at 0 °C (13.5951 g/cm3) and (2) the “standard” acceleration of gravity gn (9.80665 m/s2).
From these four definitions, the entire conversion table can be constructed.  In the tables shown below, I omit conversions involving the pound-force per square inch (a non-SI unit) and the technical atmosphere (an obsolete unit involving the avoirdupois kilogram-force).  There is nothing wrong with having these units in a conversion table; they are omitted here only because we are discussing SI units.
The first table shows exact conversion factors.  This format emphasizes the underlying simplicity of the SI, and shows clearly why the conversion factors for Torr and mmHg are different:
The second table gives approximate conversion factors (to six significant figures).  This is the format that is used in practice.  The torr and the millimeter of mercury are so similar that their differences do not appear at six significant figures.  Note the pairs of identical values scattered throughout the table:
The differences become apparent when additional significant figures are included:
          1 Pa = 0.0075006168271 Torr                           1 bar = 750.06168271 Torr  
               = 0.0075006157585 mmHg                                 = 750.06157585 mmHg
          1 atm = 760.00000000  Torr                            1 Torr = 0.99999985753 mmHg
                = 759.99989173  mmHg                            1 mmHg = 1.00000014247 Torr
          1 Torr = 0.00133322368421 bar                         1 Torr = 133.322368421 Pa
          1 mmHg = 0.00133322387415 bar (exactly )              1 mmHg = 133.322387415 Pa (exactly)
With two exceptions (noted above) these decimal conversion factors are infinitely long.  The two exceptions are exact conversion factors in decimal form.  Of course, all of the fractions in the first table are exact conversion factors.
Clearly, these distinctions are so small as to be negligible for most purposes.  However, scientific articles in Wikipedia should not tolerate ambiguities, especially when thy are misleading.
Btarski 23:12, 3 October 2007 (UTC)
thread_title: Conversion of SI pressure units

message: The statement that the torr “was used in the cgs system of units” is incorrect.  The cgs unit of pressure was the dyne per square centimeter.  It was called the barye, equal to 0.1 Pa.The Wikipedia article on the cgs system shows the torr and the barye as synonymous, which is incorrect. 
The torr was used in conjunction with both the cgs and the mks systems.  It was usually taken to mean “millimeter of mercury,” but it was also used to mean 1/760 of a standard atmosphere.  As discussed in the article, these two definitions are incompatible.
When the standard atmosphere was defined as exactly 101325 Pa In 1954; see article for reference.  Note that the standard atmosphere was originally defined in cgs units (1 atm =  1013250 barye = 1013250 newton-meters per square centimeter).  The definition of the standard atmosphere (1954) preceded the adoption of the SI (1960). the torr was defined to make 1 atm = 760 torr. The millimeter of mercury was never a part of the cgs, mks or SI systems.
 
The cgs system is now obsolete.  Any discussion of the torr in relation to the cgs system is of historical interest only. 
Unlike the mmHg, the torr (with its modern definition of 1/760 1 atm = 101325/760 Pa) is a perfectly legitimate unit of pressure, derived from SI units.  Its use in general is discouraged, http://physics.nist.gov/Pubs/SP811/sec05.htmlsince the SI unit of pressure is the pascal.
Various Wikipedia articles continue to confuse the matter by offering different interpretations of both the torr and the mmHg.  The articles on pressure, bar (unit) and pascal (unit) all contain the incorrect conversion table discussed above (under “Conversion tables”).  This table (which treats the torr and the mmHg as identical) was correct until 1954.  It has been obsolete ever since then.   
Btarski 19:01, 9 October 2007 (UTC)
replies: text: You forgot to remove it from the category as well.  I'll take care of that.  -- Gene Nygaard (talk) 17:07, 16 November 2007 (UTC)
thread_title: The cgs system

message: On the first row, third column of the table, it says 1 Pa = 1x10^5, whereas in the comment underneath explaining how to read the table it says 1Pa=1x10^5. Which is correct?
Ganaren (talk) 01:52, 7 October 2009 (UTC)
thread_title:  typo? 

message: The article currently says that originally, 1Torr = 1mmHg, but this was changed in 1954 to be 1Torr = 1/760atm. 
However, the reference given to prove this says no such thing! That reference is about a redefinition of the atmosphere (to 101325atm = 1Pa). It doesn't say anything about the torr.
Any takers...?--feline1 (talk) 10:55, 18 July 2014 (UTC)
replies: text: It is mentioned in the book I discussed one section above this one: Vacuum Science and Technologies: Pioneers of the 20th Century. Page 92, if I recall correctly. Zaereth (talk) 01:28, 25 July 2014 (UTC)
replies: text: OK and what did that book claim on the matter? :)--feline1 (talk) 19:56, 29 July 2014 (UTC)
replies: text: Hmm. Apparently the page is no longer available of google books. I'll check the library the next time I'm there to get an exact quote. As I recall from memory, the first Vacuum Symposium was held that year, where a Committee on Standards was formed for the purposes of coming up with a standardized terminology for use in vacuum measurements. The problem with mmHg is that it is a relative measurement. (For example, a person's blood-pressure may read normal at sea level, but will be very different on Mt. Everest because of the lowered air pressure.) Air pressure is constantly fluctuating, even at sea level. To work in deep-vacuum measurements, they needed an absolute reading which started at zero (zero never fluctuates). Therefore the standard atmosphere was redefined from the zero point to equal 1013250 dyn, and Torr to equal 1/760 atmosphere. (eg: 1 Torr = 1333.224 dyn.) The proceedings of the symposium are detailed in the book Advances in Vacuum Science and Technology, on page 72. Zaereth (talk) 20:42, 31 July 2014 (UTC)
replies: text: Here we go. I had a little time to do some digging. I can only find the "snippet view" of the afore-mentioned source on google, but see the third listing from the top. It shows most of the pertinent info. https://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4GGHP_enUS577US577&q=vacuum+edison+dewar+1954#q=torr+definition+vacuum+1954&tbm=bks  Zaereth (talk) 01:29, 1 August 2014 (UTC)
replies: text: I see. And does that fix the date to 1954?--feline1 (talk) 19:26, 2 August 2014 (UTC)
thread_title:  When was the definition of the torr changed? 

message: For those of us who are used to punctuation every three digits in numbers of 5 digits or more — e.g., 1 AU = 149,600,000 km (US format) = 149.600.000 km (French format?) — the "spaced-out format", 149 600 000, is a bit unfamiliar but not really confusing, once we get used to it. But when it's squeezed into a numerator in half-height type over a diagonal fraction bar...
: 
... well, at least some of us are apt to mistake that, if only briefly, for 
: 
which of course is entirely different. So I changed it to , which is at least unambiguous.
And then I went to Template:Frac to learn how to wikicode that second example, . And there I read 
: This template should not be used in science or mathematical articles, per MOS:FRAC and MOS:MATH#Fractions; use  instead.
Oh ho. So: Use
: 
to get
: 
So I did. But it happened to show on my screen with a linebreak between the number and the unit,
:                     .... 
: pascals (~133.3 Pa)
So I wrapped it in :
:  (~133.3 Pa)
to get
:  (~133.3 Pa)
which is accurate, conformant to MOS:FRAC and MOS:MATH#Fractions, and not misreadable.
To discuss this, please  me. --Thnidu (talk) 10:30, 10 March 2015 (UTC)
thread_title:  fraction format 

message: Some parts of this article come up in a Google search, but the fractions don't come through as fractions.  This might take some discussion with actual Google people to fix. Gah4 (talk) 21:06, 14 November 2017 (UTC)
thread_title:  google 

message: Should the article mention inches of mercury, way too often used in the US? I suspect both absolute and gauge pressure are used, and not always consistently. Gah4 (talk) 10:54, 17 May 2024 (UTC)
thread_title:  Inches of mercury