|WikiProject Chemistry||(Rated Disambig-class)|
Percentage solution math
Not knowing anything, I would have naively assumed that a 1% solution is a mixture of 1g of solute and 99ml of solvent. AxelBoldt 01:27 Apr 14, 2003 (UTC)
- That would make sense if 1g had a volume of 1ml. In that case you would have a % v/v solution. Howver for a w/v (weight/volume) there is little point in only having 99mls of solvent, since most solutes don't have 1g/ml density. Theresa knott
I think it should be mentioned that a % w/v solution is somewhat of a mathematical impossibility. Since weight and volume are measured in different units, a w/v ratio can never be specified unitless as per cent. The appropriate unit would rather be kg/m3 or something similar. w/v does not make sense unless units are also specified. This unit is, however, mainly used within the fields of biology and medicine, by people that rarely have the mathematical knowledge to even notice this flaw. — Preceding unsigned comment added by 188.8.131.52 (talk) 08:56, February 17, 2006 (UTC)
- Yep these solutions are approximate. When a biologist wants an exact solution they use molarity the same as everyone else. Theresa Knott | Taste the Korn 10:54, 17 February 2006 (UTC)
- These solutions are not more approximate than a molar solution; that only depends on measurement precision. They are, however, not suitable to be described as percentage solutions, but rather using an appropriate unit. Unfortunately this highly ambiguous notation is too often used in biology and medicine as well as in chemistry (less common, though). But as these are mostly my own views I am not sure if it is really appropriate for me to make too much of a deal out of it in the article. It would on the other hand be interesting to hear someone who actually uses this (incorrect) notation motivate its use. — Preceding unsigned comment added by 184.108.40.206 (talk) 11:46, April 28, 2006 (UTC)
User AxelBolt is actually correct if the solvent is water. The convention is, when no units are specified, it is w/w. A m/v solution should specify the units, as someone already wrote; although it is often not specified, and is often assumed to be g/mL (or equally, kg/L). Further, the notion that a 10% w/v solution is prepared by mixing 10 g of solute with 100 mL solvent is wrong. A 10% w/v solution is prepared by mixing 10 g of solute with enough solvent to make 100 mL of solution. The first method will yield a solution that is only approximately 10% w/v. For this reason, "w/v" should not link to this article, but to concentration instead. As for "percentage solution" as currently defined by this article, is this just a common mistake or is it really defined by biologists as such?--220.127.116.11 04:33, 18 May 2006 (UTC)
Please forgive me if my math is incorrect, but I calculate 1% w/v of 100ml to be 1g and 1/342.34 mol/g * 1g = 2.9mMol, not 29mMol. — Preceding unsigned comment added by 18.104.22.168 (talk) 21:44, July 3, 2007 (UTC)
- Good points from "22.214.171.124 04:33, 18 May 2006 (UTC)", "Preceding unsigned comment added by 126.96.36.199 (talk) 21:44, July 3, 2007 (UTC)", and "--188.8.131.52 (talk) 05:54, 9 April 2008 (UTC) (nev)". A few years has lapsed since those comments, and still there is no one entered correction. Interestingly, the discussion on this entry has been pretty active all the time though. However, people are more interested in entry-merging rather the essence, value of the entry. It is time to put my correction in here. By the way, the formula
- does not match the definition given in this entry either. It should be
- By the way, biologists use the same definition as chemists and every body else when they got it right. The one at "184.108.40.206 04:33, 18 May 2006 (UTC)", I am a biologist.--Achian (talk) 16:18, 21 March 2011 (UTC)
This information also on Concentration page
This page seems redundent. Percentage solution is a measurement of concentration and is properly explained on the Concentration page. I suggest we redirect Percentage Solution to the Concentration page. Grayob (talk) 16:18, 2 June 2009 (UTC)
- I disagree. If you delve deep into it, percentage concentration is more complex than it appears on the surface. There have been discussions, or usages, in the literature that include all combinations: weight/volume, weight/weight, volume/volume, volume/weight, weight/volume. The basic idea is from the factor that water's density is 1 gram per milliliter. Therefore the it appears, at least to some, the weight denominator is possible. Percentage solution deserves a separate entry. Otherwise it will mess up the co-merged entry.--Achian (talk) 16:17, 21 March 2011 (UTC)
Using % to express concentrations.
Anyone reading this page should also consult the page "Percent sign".
In the International System of units (S.I.) % is a well defined symbol that can be replaced by "x 0.01" (multiply by 0.01) or equivalently "÷ 100" (divide by 100). In S.I. any quantity expressed as x % where x is a number must itself be a number. Ratios of volumes or ratios of masses are just numbers and thus these can be expressed using the % symbol. It is common at least in the biological literature to refer to the concentration of a solution containing 1 g of solute per 100 mL of solution as 1 %w/v. In light of the above it would be much better to state the concentration in terms of units for mass and volume, e.g. 10 g/L or 10 mg/mL. A careful statement of these matters can be found in section 7.10.2 of the publication "The NIST Guide for the use of the International System of Units" by A Thompson and B.N.Taylor, which can be consulted or downloaded at http://www.nist.gov/pml/pubs/sp811/index.cfm. SteveElemMaths (talk) 13:56, 18 October 2010 (UTC)
- Yup. But, this article discusses a common usage and terminology and we're not here to correct the biologist's terminology - just to report and try to explain what they mean. Vsmith (talk) 16:42, 18 October 2010 (UTC)
Really misleading explanation of % w/v both here (where you forgot to put units!) and if ine follows the link. Correct answer seems to be that 1 % w/v is 1g per 100mL. There is no chance anyone can deduct that info from the current wordings!