Talk:Litre

From Academic Kids

See http://www.npl.co.uk/npl/reference/international.html for 1979 acceptance of L as well as l. Hotlorp 23:29 Feb 14, 2003 (UTC)

The year of 1901 cannot be right, can it? I thought the Imperial gallon being defined by so and so measure of water was inspired by the metric definition of a litre, so it must have been at the start of the 18th century -- Egil

You are right: the litre is older than 1901. See the current article. -- Heron

Added kilolitre - my water bills in Australia used to measure consumption in kilolitres. - David Gerard 12:54, Jan 28, 2004 (UTC)

Circular dependency?

Nothing depends ON litre, so no matter what litre depends on, there cannot be any circular dependency, can it? --Mormegil 10:21, 10 Aug 2004 (UTC)

Good point, removed this from the article. Paranoid 18:57, 20 Nov 2004 (UTC)

Reasons for redefinition

Does anyone know why the litre was redefined in 1901? It doesn't make any sense to me, when you had a perfectly good definition based on the metre. Paranoid 18:57, 20 Nov 2004 (UTC)

It was indeed rather senseless, IMHO, but the CGPM did finally come to their senses and "abrogate" that definition (that's how it is phrased in the legalese of their resolution).

Originally, it was intended that the gram should be the mass of a cubic centimeter of water; so obviously the length standards were constructed first. But then, way back in 1799, the original platinum cylinder known as the Kilogramme of the Archives was constructed by the French government to serve as the mass standard. Since then, the definition of the kilogram has never been officially based on water.

After the Metre Convention (or Treaty of the Meter) of 1875, the organizations known as the CGPM and BIPM were formed. They has a new set of international standards for the metre and the kilogram constructed, placing them in use in 1889. In constructing this new platinum-iridium International Prototype Kilogram and its siblings which serve as national standards, the target was the old French standard—not water.

But by then, in the late 19th century, people had been able to make better measurements of the density of water, at its maximum density and throughout the temperature ranges of liquid water, and were well aware of the discrepancies between the actual kilogram, and what it would have been if the 18th century French technicians had been able to carry out these measurements more precisely in constructing their kilogram.

Obviously, there were some users in the science who thought it was terribly important to have that exact relationship with water at its maximum density. So the CGPM let itself be talked into this hairbrained scheme of redefining the litre to make that true (I wouldn't call it that in the article, but am expressing my opinion of it here on the Talk pages).

Note that this is a flip-flop of the original intention of defining the unit of mass based on the cube of the unit of length. In 1901, they instead redefined the unit of volume based on the unit of mass.

Cubic centimeters, of course, remained the cube of the length units. So for a couple of generations or so, we students had to waste a lot of time learning that they were not the same thing as milliliters. Never mind that there had only been a handful of measurements in the history of the world where it ever made any difference.

There was, of course, a similar discrepancy in the construction of the original metre, from their very good but not as good as today's efforts to measure the meridian quadrant, and as a result there are actually 10.002 Mm from the equator to the poles, rather than the intended 10 Mm exactly. Fortunatly, the CGPM never got talked into any scheme to add another new length unit to use alongside the metre, but equal to 1.0002 m.

Note that I have removed an erroneous claim in the article as I found it that the intent in 1901 was that the 1901 definition would be the same as a cubic decimetre. It was well known that it would not, and that in fact was the entire purpose of that redefinition, to make it different from the cubic decimeter which for water never quite gets up to that 1.00000 kg level under one atmosphere of pressure, even at maximum density. Gene Nygaard 03:12, 13 Dec 2004 (UTC)

Symbol mL

CGPM in 1979 said:

considering further that in the future only one of these two symbols should be retained, invites the CIPM to follow the development of the use of these two symbols and to give the 18th CGPM its opinion as to the possibility of suppressing one of them.

The CIPM, in 1990, considered that it was still too early to choose a single symbol for the litre.

The United States National Institute of Standards and Technology recommends the use of the uppercase letter L.

Uppercase L has become the preferred and more common symbol in US & Canada. It only makes sense that the others (mL) use capital too - otherwise there's confusion.

Are there any standard bodies recommending lowercase be retained?

I'd say "the handwriting is on the wall" - there's not a chance in hell that lowercase will be the single symbol --JimWae 18:50, 2004 Dec 14 (UTC)

Capacity v. Volume

Can anyone give a practical or commercial case in which the litre is used for solids? --JimWae 18:50, 2004 Dec 14 (UTC)

Certainly. Grain might flow, but it is not a fluid. Same goes for blueberries (where in the U.S., the 1 pint packages also include 551 mL right on the label, for example). Gene Nygaard 20:58, 14 Dec 2004 (UTC)

Here's another example, from http://www.stainless-steel-world.net/titanium/automotive.asp

Comparison of specific strength of engineering alloys

Material	Density kg/l	Youngs Modulus GPa	Yield Strength MPa	Specific Strength
CP Titanium	4.51	105	250 - 450	50 - 100
Ti-6Al-4V	4.43	112	900 - 1100	200 - 250
Ti - LCB®®	4.79	110	950 - 1400	200 - 290
Carbon Steel	7.8	200	350 - 450	45 - 60
Aluminium Alloy	2.8	70	100 - 350	35 - 125

Gene Nygaard 21:18, 14 Dec 2004 (UTC)

The capacity of a garbage bag is not the measurement of a fluid. Sure, it is the volume of a fluid such as air which would fit into it. But that's not usually what we use our garbage bags for. Gene Nygaard 21:41, 14 Dec 2004 (UTC)

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I guess it could be different in different countries, but we do not buy rice or wheat or or candy or aluminum by the litre in Vancouver - not retail, & I doubt wholesale too.

Blueberries & strawberries come in CONTAINERS with a certain mL capacity ( I notice you used mL too) & no weighing is then needed. Would anybody really expect they are getting 551 mL of blueberries without the air?

I think derived units for density using kg/L might stay current because it is an obvious way to compare to water that way.

I was taught litre was for capacity (and "fluids" & even small solids that flow that are not normally counted & usually get no indefinite article; e.g rice - not a rice, but yes an apple), m^3 was for volume. Though it is not a hard & fast rule, it is noteworthy enough, I think, to include somewhere in the encyclopedia (admittedly, not in the definition) - and I think clearer.

The Wikipedia isn't just a British Columbia project.

Look at any Canadian table of conversion factors for bushels (at least by anyone not smart enough to know that most of the bushels we use today are units of mass). What are the metric units used? What do we measure with bushels?

Google bushel hectoliter OR hectoliters OR hectolitre OR hectolitres OR hektoliter

The site http://www.bcblueberry.com/processors/production.htm tells us that

"Fresh BC blueberry packages include:

• five and ten pound bulk cases,

• and trays containing twelve one-pint

• or twelve half-pint units and other sizes."

Of course, there are a couple of differences between your British Columbia blueberry boxes and mine in the United States:

1. Those Canadian containers do not include the word "pint" or an abbreviation of it on the label.
2. Those pint containers are 568 mL rather than 551 mL. That's because you use those dinky little litres instead of the hefty liters we use, isn't it?  :-)

That there are air spaces among the berries does not mean that you are measuring a fluid.

For wheat in Canada, the "test weight" (a measurement of bulk density, used as a quality factor) is still very often measured in pounds per U.S. bushel (rarely if ever per imperial bushel). But you also see it expressed in metric units, such as the "kg/hl" at http://members.shaw.ca/bethcandlish/swht1.htm

Yes, I used mL too. But I when I commented on your web page, what I said is that it is not good form to change someone elses "ml" to "mL' in Wikipedia. (Trying to achieve consistency within one article might be acceptable, not just flip-flopping from one to the other). For this particular article, and probably not any other, I think it would be a good idea to include both in all uses, but I'm not going to add that now.

Those density usages are quite relevant to the untruth of the limitation you claim.

Whoever the anonymous person was who deleted your statement about liters only being for fluids got it right. (Well, actually I'm just assuming you are the one who put it in there; it doesn't matter enough to me for me to go and confirm that--it's good riddance to misinformation in any case.) Gene Nygaard 01:25, 15 Dec 2004 (UTC)

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OK, I'll agree "for fluids" was incomplete. It is also incomplete to leave it open to use litres for measuring quantities like solid metals.

Litres (& mL & kL) are used for things that are measured by the capacity of their containers - usually (but not exclusively) things that can be poured & that are non-count nouns (and usually in English anyway, get no indefinite article).

Water in a swimming pool would then be measured in litres, water falling over Niagara in m^3 - You will rarely see waterfalls measured in litres (though of course some will do so) -- the water is not in a container.

There may be exceptions to this too, but it is still noteworthy in an article about litres.

Noting also: Many things that can be poured are sold by mass anyway.

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A note was deleted which stated that the unit of volume in the SI is the m³. This should be reinstated. It is correct. The m³ is the derived unit of volume in the SI. NIST note on SI units (http://physics.nist.gov/cuu/Units/units.html)

The liter is defined as one of the "Units outside the SI that are accepted for use with the SI." It is not, strictly speaking, a unit in the SI, and should not be represented as such. NIST note on units outside the SI. (http://physics.nist.gov/cuu/Units/outside.html)

I also find the statement above, "Litres (& mL & kL) are used for things that are measured by the capacity of their containers" to be very dubious. Can the author point to *any* publication by any authorative standards body that states this? I've never seen such a thing, and would find it hard to believe that any standards body created another unit of measure for volumes strictly based on intent. --Eliasen 03:08, 19 Dec 2004 (UTC)

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You have said

• The liter is defined as one of the "Units outside the SI that are accepted for use with the SI."

Whereas The 12th Conférence CGPM does not even define the litre, saying that it

• declares that the word “litre” may be employed as a special name for the cubic decimetre,

so it does not DEFINE it at all, but gives an equivalancy in common use - it certainly does not define it "as one of the units outside the system", but further declares

• that the name litre, although not included in the Système International d’Unités, must be admitted for general use with the System,

I've lived in a country that has used SI for 30 years. No current standards body created the litre - it is simply a unit in common use that "must be admitted for general use with SI - just like the minute and the day

The unit is not based on intent but on how the measurement is done.

If L (or mL or kL) are used, then (at least most likely) it has been measured by the size of the container it is in.

If kg are used, the expectation is that its weight or mass have been measured.

If m³ is used then (at least most likely) its dimensions have been measured -- OR its displacement.

I am really quite surprised that I cannot find a standards body that distinguishes capacity from volume -- What is the volume of a cubic container each of 6 sides a square of 11x11 cm, with each side 5 mm thick? What is its capacity? Remove 1 side and recalculate. There's some difference between volume & capacity, right?

I guess the standards bodies just do not want the added responsibility of defining a litre or its uses - so it would seem we cannot appeal to standards bodies but only to common usage Or perhaps it just is not their venue to make the distinction, maybe it's up to linguists or philosophers. --JimWae 05:38, 2004 Dec 19 (UTC)

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