# Another math/chemistry question **URL:** \ **Category:** Factual Questions\ **Created:** [November 13, 2008, 6:32pm UTC](https://boards.straightdope.com/t/another-math-chemistry-question/472566 "2008-11-13T18:32:19Z")\ **Posts on this page:** 4\ **Page:** 2
**Author:** ![masterofnone](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@masterofnone](https://boards.straightdope.com/u/masterofnone)\ **Post date:** [November 13, 2008, 8:31pm UTC](https://boards.straightdope.com/t/another-math-chemistry-question/472566/21 "2008-11-13T20:31:41Z")
This does not directly answer your question, but may be useful:[Aviagen reccomends 8-16mg/lb body weight](http://www.aviagen.com/docs/Intestinal%20Worms_TUVol1.pdf). ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 13, 2008, 8:43pm UTC](https://boards.straightdope.com/t/another-math-chemistry-question/472566/22 "2008-11-13T20:43:05Z")
> [@WarmNPrickly](#): > > You add the solid, then fill it to a liter. Yes, that means that you don’t add a full liter of water. Actually, it sometimes means adding _more_ than a liter of water. When mixed with water, some materials actually _decrease_ the total volume. [Ethanol](http://www.newton.dep.anl.gov/askasci/chem03/chem03197.htm) is notorious for messing with final volume, but other substances can do so as well. ---
**Author:** ![mnemosyne](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@mnemosyne](https://boards.straightdope.com/u/mnemosyne)\ **Post date:** [November 13, 2008, 9:16pm UTC](https://boards.straightdope.com/t/another-math-chemistry-question/472566/23 "2008-11-13T21:16:03Z")
Does anyone have access to a copy of the USP/NF? Or the EP? or the JP? All three pharmacopeia will tell you how to prepare solutions _as approved for use_, which would settle this pretty quickly. Any pharmaceutical chemists out there (I was one, but I went back to school!) FWIW, barring any other information, I would make the solution with 135 g of solid, plus 1000mL water, added to a container and dissolved. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [November 14, 2008, 1:53pm UTC](https://boards.straightdope.com/t/another-math-chemistry-question/472566/24 "2008-11-14T13:53:04Z")
> [@mnemosyne](#): > > Does anyone have access to a copy of the USP/NF? Or the EP? or the JP? All three pharmacopeia will tell you how to prepare solutions _as approved for use_, which would settle this pretty quickly. Any pharmaceutical chemists out there (I was one, but I went back to school!) > > FWIW, barring any other information, I would make the solution with 135 g of solid, plus 1000mL water, added to a container and dissolved. Agreed that you should follow the industry-recognized standard method for preparation of solutions. What’s most important is that everyone follow the same convention. That being said, a thought occurred to me while working out last night: The units don’t actually work out for w/v %. For w/w %, it doesn’t matter what mass/weight units you use (e.g. grams, mg, lb, etc.), so long as you use the same units for the solute and solution. The same is true for v/v %. It doesn’t matter what volume units you use (e.g. mL, gallons, etc.), so long as you use the same units for the solute and solution. However, for w/v %, this is not true. Generally, grams are used for the mass of solute, and mL are used for the volume of solution. These units do not properly cancel to give a percentage. The only reason it generally gives a reasonable approximation is because 1 g of aqueous solution has a volume of approximately 1 mL. However, this approximation becomes increasingly inaccurate for concentrated solutions. IMHO, it would be more accurate and less confusing to simply leave the units in place (e.g. g/mL) than to try to express it as a percentage–or use w/w %. [Previous page](https://boards.straightdope.com/t/another-math-chemistry-question/472566.md?page=1)