I'm trying to determine how best to mix some chemicals. I'm making a
potion that should end up being 1% tolnaftate and 5% methyl salicylate
in iso alcohol 99%. I have the chems; what is an easy precise way to
mix them? The tolnaftate came in a 1gm pouch...seems like a VERY small
pouch for the money...think I need to be very precise! (no i don't
have a chemistry background!)

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Request for Question Clarification by andrewxmp-ga on 18 Apr 2004 21:38 PDT

Could you describe the exact way you obtained these values?  From some
sort of product sheet or something: where did you obtain this
"recipie"?  It's possible the solid components were actually described
as a concentration of some sort.  Any informatino of this sort would
be very helpful, thanks.
-Andrewxmp

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Clarification of Question by shuvel-ga on 18 Apr 2004 22:00 PDT

ok, to clarify...1) the methyl salicylate is a liquid, just the
tolnaftate is solid. its a recipe I decided on after mixing commercial
brands together. I would take athletes foot powder (they all seem to
be 1% tolnaftate) and I would add it to surgical spirits (a
wintergreen smelling alcohol...a british term). I believe the surgical
spirits is iso alc. w/5% methyl salicylate. (could actually be
menthol..is that the same thing?) I would add as much powder to the
alc as I could. So I want to bypass the commercial products and make
my own, make sense? HTH

Hi shuvel,

Thanks for the clarification- I was pretty sure beforehand, but just
wanted to check.  Because you are working with a solid (and also
because this is simply the standard way in which this type of mixture
is described), you need to use a mass/volume percent solution. 
Standard chemistry notation when describing a ?percent solution? uses
the metric units of grams (g) and milliliters (mL), and is as follows:

?There are other percent concentrations involving expressing the
solute in mass terms and the solution in volume terms. This is called
Percent (m/v) and is defined:

%(m/v) = mass of solute in grams (100) / volume of solution in ml?

[ http://members.aol.com/profchm/masspct.html ]

It is also similarly definied at:

?Percent (%) solution: Weight of substance (g) per 100 mL of solvent
(w/v) or the volume of a solute (mL) per 100 mL of solvent (v/v). ?

(from page 11 of the PDF-format document found  here:
[ http://www.cor.uams.edu/Basic%20Math%20&%20Chemistry.pdf ]
or html-format document here:
[ http://216.239.51.104/search?q=cache:zm4mwMvZ3wsJ:www.cor.uams.edu/Basic%2520Math%2520%26%2520Chemistry.pdf+chemistry+mix+dry+chemicals+liquid+concentration+grams&hl=en&ie=UTF-8
])

So, for your solution, you would need to mix the following:

1 gram of tolnaftate
5 mL of methyl salicylate
95 mL of iso alcohol         +

=100 mL of solution total

Or you could always use some percentage less than this if you don't
want to use all of your tolnaftate powder; simply reduce the values by
the same ratio.

The volume displacement of the tolnaftate power is technically NOT
considered negligible in a percent solution, even though it is very
small, so the way you want to mix those chemicals is as follows:  Get
a flask of some sort with precise markings, add the 1 gram of
tolnaftate and the 5 mL of methyl salicylate, and then fill the flask
up the remainder of the way up to the 100 mL mark.

Let us know how the solution turns out!


I trust this has answered your question satisfactorily.  If you
require a clarification, please request one, especially before rating
this answer.  Thank you for bringing your question to Google Answers!

Regards,
Andrewxmp

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Request for Answer Clarification by shuvel-ga on 19 Apr 2004 11:51 PDT

I'm thinking that is probably a great answer, but it leaves me a
little worried. Are you sure that one gram tolnaftate powder mixes
with the 100ml of liquid? The 1gm vial I have cost about $50 and that
would end up being a solution that is 10 times as expensive as a
similar solution at a drugstore. i bought the vial at a chemical
wholesaler. Are you sure its not one tenth or one hundredth that
amount? I have verified that commercial solutions and powders claim to
be 1% tolnaftate.

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Clarification of Answer by andrewxmp-ga on 19 Apr 2004 12:21 PDT

Shuvel,

Without a spec sheet from the manufacturer of the commercial substance
you're trying to reproduce, you could not be absolutely sure that this
is the right "recipie".  However, this is the only correct way that
chemical concentrations are described, and I see no other way that a
1% solution would be mixed.  As for the price difference, I understand
you went to a wholesaler of some sort, but even so, it is probably
just a matter of economics: the companies that manufactures these
cremes simply produce an extraordinarily large amount of this stuff,
and thus can do so very cheaply.  The most important factor, it seems,
is that anti-fungal ointment is the only use I could find for
tolnaftate with a breif search.  Since the amount of it used for other
uses is probably very very small, a chemical company selling it to the
public can probably charge quite a bit for it, because it would be a
relatively obscure request.  All together, I do believe the
description above is the right concentration for you to use; the
difference in price is simply a matter of economic supply and demand
that someone in your position has caught the unfortunate end of.  I
hope this clears this matter up, but If we need to do more research on
the subject, please let me know.

Regards,
-Andrewxmp

Great answer! exactly the info I was looking for...thanks!

I agree with the answer given.  Percent compostion can also be
calculated in terms of mass/mass or volume/volume (vol/vol is a bit
tricky when one compontent is a solid).  However, the main component
is isopropanol, which has a density not too far from 1g/ml, you will
(I think) get pretty close to the same numbers regardless of how you
calculate the percentage.

Off the top of my head, I think the density of isopropanol is about
0.8 g/ml, so if you made a solution that was 1% by mass/mass, you
would end up about 20% more dilute than a 1% mass/volume solution.

wow, i'm really feeling like an idiot now: Is it also true that a 100g
bottle of the Tinactin powder which is marked tolnafate 1% and sells
for less than $10 has about 1g of tolnaftate in it?