# Help with solution concentration

#### Noclue

##### New member
Hi I'm looking for some help that I think is easy but just can't get my head round.
So I need to make a solution with a concentration of 10% bleach to remove DNA contamination from equipment. So if I had 100ml of water I'd need 10ml of bleach to make a 10% solution. But it is the active chlorine in bleach that removes DNA so I'm trying to work out a calculation of how many ml of bleach I'd need if the active chlorine concentration within the bleach is 4.47g per 100ml. Can anyone advise how I work out the ml of beach needed to get 10% solution.
Thanks.

#### Klaas van Aarsen

##### MHB Seeker
Staff member
Hi I'm looking for some help that I think is easy but just can't get my head round.
So I need to make a solution with a concentration of 10% bleach to remove DNA contamination from equipment. So if I had 100ml of water I'd need 10ml of bleach to make a 10% solution. But it is the active chlorine in bleach that removes DNA so I'm trying to work out a calculation of how many ml of bleach I'd need if the active chlorine concentration within the bleach is 4.47g per 100ml. Can anyone advise how I work out the ml of beach needed to get 10% solution.
Thanks.
Hi Noclue, welcome to MHB!

If I'm not mistaken, a 4.47 g of active chlorine bleach per 100 ml of water, is a 4.47% bleach solution.
A typical household bleach is a 3–6% solution in water.
We can't get from there to 10% with just mixing.

#### DavidCampen

##### Member
It would help to see the actual text that you are trying to interpret. I would guess that "bleach" refers to standard household bleach and that they are saying to make a solution of 1 volume of household bleach added to 9 volumes of water.