[jamalmaya]

Dear Friends! I am looking for an answer on how to dilute this solution of 10% povidone iodine to 0.05% povidone iodine solution  . 
at  the moment I am thinking of using the MV=M'V' formula.
M=molarity
V= volume

however i donot know what the molarity for the 10% povidone iodine is;  and i donot know what molarity for the 0.05% povidone iodine is. So I found the MV=M'V'  formula not helpful.

Your help is greatly appreciated
Many thanks 

my email : jamalmaya@yahoo.com

[sjb]

Dear Friends! I am looking for an answer on how to dilute this solution of 10% povidone iodine to 0.05% povidone iodine solution  . 
at  the moment I am thinking of using the MV=M'V' formula.
M=molarity
V= volume

however i donot know what the molarity for the 10% povidone iodine is;  and i donot know what molarity for the 0.05% povidone iodine is. So I found the MV=M'V'  formula not helpful.

Your help is greatly appreciated
Many thanks 

my email : jamalmaya@yahoo.com

Assuming that the 10% and 0.05% are both the same measure, be it e.g. w/w, v/v or similar, then you don't actually need the molecular weight or the molarity, to a good approximation. Try it for a fixed molecular weight, x, and see for yourself.

[jamalmaya]

sjb Hi  ! Thank you for your kind reply.

i am reading your advise many times, and i think, i'm getting the message....
i will try out some calcution now and see what happens   

Thank you again

[jamalmaya]

Dear sjb! Hi again 

I think i've found the answer! but i just want to double check with you first.

using the same formula: MV=M'V'

where the M and M'  are unknown molarity, and V and V'  are the Volume.
On the left side of the above formula, i have put in:
10/100 x 5mL
(10/100 came from 10% povidone iodine solution,and 5mL is the quantity used.)

on the right side of the formula, I have put in
0.05/100 x V' mL
(0.05% came from the 0.05% povidone iodine, and the V' is the required dilution to be added to the previous 5mL of 10% povidone Iodine.)

the answer to the above formula,  V'= 1000mL

so, is it true that 5mL of 10% povidone iodine, when added to 1000mL of saline solution, will give rise to a solution of 0.05% povidone iodine  ?

Thank you for reading my question...

[sjb]

So close.

If the povidone iodine was in saline initially, then diluting it with brine is fine.

The maths is right, however the conclusion is not. Think about what you've said

If you had 10% originally, and you needed 5%. By your calculation you'd need twice the volume of solvent. But then you are adding that volume to your initial volume, which is wrong. 5 ml of solution made up to 1 litre would be 0.05 %, not 1 litre of "blank" + 5 ml of active.

[jamalmaya]

Dear sjb!
Thank you very much for your kind reply.

I am pondering now on what you have explained.
I will need to think this over ,first thing in the morning when my mind is at it's best

Cheers !