Proportions for a Chemical Solution

Date: 6/24/96 at 13:47:3
From: William B. Fair
Subject: Formula for a Chemical Solution

I need some help in my basic math on mixing up percentage formulas.
For example, if I want a 10 percent solution of a particular chemical 
that comes in powder form what would be the formula to solve this?  

I've used amount desired times percent desired divided by percent on 
hand for all of my liquid formulas, but now that a powdered chemical 
has come into play I'm sure you just don't use an equal weight in 
grams, say 10 grams in a 90 ml. beaker, and expect to get a 10 percent 
solution.  Or is it that simple?  

I hate to take your time up with something so basic, but other than to 
the library and research this out I had hoped that the Internet could 
help me out, and you were my first choice.

Thanks -
            Bill

Date: 6/24/96 at 20:15:41
From: Doctor Anthony
Subject: Re: Formula for a Chemical Solution

I am not a chemist, but if you are mixing chemicals by weight, then 
for a mixture containing 10% of a particular substance, in every 100 
gms of the mixture, 10 gms will be of that chemical. If you are mixing 
by volume, then clearly you would add 10 ml to 90 ml to get 100 ml of 
the mixture. I note that you were confusing mass and volume when you 
suggested 10 gms and putting this into a 90 ml beaker. I think you 
should consult a chemist as to whether it is by mass or volume that 
you are meant to be working.  If it is by volume you would doubtless 
first dissolve the chemical at at a quoted mass for a given volume of 
water, and then mix this liquid by volume with the other chemicals in 
the ratio 1 : 9.

-Doctor Anthony,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/