1. ## dilution formula

Could someone please help me with this formula, I'm sure it's pretty simple but I don't know how to do it.

What I need is a formula for dilution.

I have 10 ml of liquid that is at a strength of 500 ppm.

How would I make a formula to figure out how much liquid to add that has a strength of 0 ppm to the 10 ml of liquid that has 500 ppm, to come out with a liquid of 4 ppm?

For example if I add 90 ml of 0 ppm liquid and to this liquid I add 10 ml of 500 ppm water - I would have a final liquid that was 100 ml in size with a strength of 50 ppm.

Thanks,
Bill

2. Originally Posted by billionzz
...
What I need is a formula for dilution.
I have 10 ml of liquid that is at a strength of 500 ppm.

How would I make a formula to figure out how much liquid to add that has a strength of 0 ppm to the 10 ml of liquid that has 500 ppm, to come out with a liquid of 4 ppm?...
Hello, Bill,

let c1 be the concentration of effective substance in the 1rst solution
let v1 the volume of the 1rst solution

let c2 be the concentration of effective substance in the 2nd solution
let v2 the volume of the 2nd solution

These 4 values must satisfy the equation:

c1 * v1 = c2 * v2

(c1 * v1 is the total amount of effective substance which doesn't change here)

You already know 3 of these values, thus you can calculate the 4th one:

500ppm * 10 ml = 4 ppm * v2

v2 = 1250 ml that means you have to add 1240 ml.

EB

3. That's what I was looking for, you really cleared it up for me.