Talk:Specific gravity
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i am not a scientist, but i believe the density of water should be 1000kg/m3, not 1000kg/m-3 as stated on this page. hopefully someone more qualified will edit the page so that readers are not confused. apologies if i'm wrong -- i checked other web pages. Ejj357 (talk) 20:55, 29 March 2008 (UTC)ejj357
- actually, u quoted it wrongly.
1000 kg·m−3 is what is in the article. The '.' kindoff refers to * so its really 1000kg*m−3 which would read 1000kg per cubic meter. ie: its correct, nothing wrong with it. Thx for the headsup!--Venny85 Venny85 21:05, 29 March 2008 (UTC)
[edit] Discouragement of specific gravity?
- About the use of specific gravity being discouraged in tecnical use. I am aware the use of specific gravity in the everyday world and still taught, as a scientist who tries to reduce ambiguity in my work, I see it necessary to include this in the article because of the importance of the particular issue...in the reference for example references itself to publications from IUPAC (1993) and ISO standards Handbook 2 (1992) and the reference clearly states in the definition that the term is now discouraged. I was trying to make it clear that in a technical sense that actual density should be used because specific gravity is usually calculated or determined by buoyancy concept for example. It also a known fact that the density of water is neither constant (see VSMOW) nor has a "true" density of 1000 kg/m3. I am just trying to keep truth and up to date information so others can have a better view of the term. —Preceding unsigned comment added by Jmmeadows (talk • contribs) 03:59, 15 April 2008 (UTC)
I figured the relation would be best located next to initial sentence of the entry. Sorry about that.
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- Actually, thats not really true. Specific gravity is used in many technical and operational instances. It is used to calculate API gravity in oils, viscosity unit conversions, grading of various petroleum products, calculation of ship loading capacities etc etc. It is a very commonly used number in the real world, definitely not discouraged in any way. You mention that specific gravity is not used in any scientific field requiring high precision, however, specific gravity wasnt meant to be a scientific term, but rather a working, practical term with real uses. It wasnt coined as a synonym of sort with scientific terms like density. ie: specific gravity is a kindoff borrowed industrial term never meant for use in scientific measurements. Not because 'density of water is neither constant' (most substances have densities that vary with temperature), and "true" density is never mentioned but density is always mentioned with a temperature attached eg: 1000kg/m3 @ 4C. The next line after you inserted your text clearly defines the term used scientifically: 'synonymous with, relative density, with the latter term often preferred in modern scientific writing.' This line clearly differentiates the uses of the various terms in different fields in different contexts. Venny85 (talk) 17:02, 15 April 2008 (UTC)
I see exactly where your coming from, in many cases most references commonly state water's reference density as being "exactly" 1000 kg/m3 (I see that too often). When your dealing with 4 to 5 signifigant figures, I agree with you for sure. Over the years I've seen many times where specific gravity is used in formulations for calculating the mass of solute from mass percent and specific gravity, sure it is fine when for a reasonable approximation, but in the instance of diluting a concentrated acid for instance, it is strongly recommended instead of using a volume of acid that it is measured by mass. And in the article of relative density, it is clearly a "relative" density, not true density and the relative reference material must be striclty adhered to. Most assume that water is the same all over the globe (isotopic composition), most do not take that into account, you see where I'm coming from? But in any case as long as the refernces are made clear than sure it is ok depending on how deep they wanna go. Anyways have nice day and thanks for talking because everyones input is important because they do like to change the rules on us and can lead to many differentiating opinions, which is what helps us tomorrow and so on.
[edit] Density not weight?
I changed denser back to heavier because heavier is a concept that is easier to understand and because both statements are equally true. So why was it changed back to denser with the statement "density not weight"? Thanks. Mmyotis ^^o^^ 15:12, 28 May 2008 (UTC)
- Ahh, never mind. I suppose it should read heavier (per unit volume), which is just a complicated way of saying denser. Mmyotis ^^o^^ 15:17, 28 May 2008 (UTC)
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- Well your not too far off the mark. See specific weight. It's just awkward to say "higher specific weight" then is is to say "higher density". Also g is constant for specific gravity, so it is simpler to use density for the higher/lower comparison. I'd hope if a reader were reading this article they would have grasped the physical concept of density. +mt 17:19, 28 May 2008 (UTC)
