hi, using this formula M1V1=M2V2

M1-molarity of stoke solution

V1=volume of stoke solution

By using C1V1=C2V2

Here your C1 is 40mg/ml and C2 is 30mg/ml. Suppose you want to make 10ml of your 30mg/ml plant extract. Therefore, your V2 is 10ml. Now you need to know how much volume from stock solution you need to take to make 10ml of your working concentration.

So just put all the values in the equation.

40mg/ml × V1= 30mg/ml × 10ml

V1 = 7.5 ml

So take 7.5ml from your stock and add 2.5ml of your solvent in which your extract was dissolved.

The answers of Dr. Mokhtar and Bhaswati is very correct.

Depending on the volume you need, you can just make substitute. However remember you need to make up to volume e.g. 7.5 ml make up with 2.5 ml of solvent to give 10 ml and not 7.5 ml +10 ml (wrong).

Let us assume that your final volume with 30 mg/ml will be 100 ml.

Then from a solution of 40 mg/ml you are going to prepare 30 mg/ml solution and the remaining has to be diluents.

So ,

40X=100ml

X=2.5 ml

Then, multiply the desired concentration with the above factor 30*2.5, which is 75; then mass up the 75 ml volume of solution with a concentration of 40mg/l with distilled water to one litter ( 25 ml distilled water)

For sake of simplicity, I have prepared simple chart. see it. It is similar to dilution principle. C1V1=C2V2

C1V1=C2V2, I agree

Thanks to all my Respected Seniors for this informative answer.

hi, using this formula M1V1=M2V2

M1-molarity of stoke solution

V1=volume of stoke solution

www.sciencedirect.com/science/article/pii/S2221169115309114

regards

I agree with Bhaswati's answer

You must use V1 xC1 = V2 x C2 . And ready..!!

The answers of Dr. Mokhtar and Bhaswati are very correct.

Regards