Dilutions - don't be scared!
Dilutions tend to worry first years! These come up a lot in 107 and 109. I think a lot of you just don't get along with the terminology that is used when people talk about dilutions. Let me try to clarify things a little...
Sometimes, dilutions are talked about in terms of ratios. i.e. a 1:2 dilution or a 1:3 dilution.
Remember that ratios tell you how much of one thing there is in comparison to another thing.
So, for a 1:2 dilution (which could also be written as a '1 to 2 dilution'), this means that there will be one 'part' of one thing and two 'parts' of a second thing, and therefore three 'parts' in total.
Example:
If you were asked to make a 1:2 dilution of a 60 mM NaCl solution, and the final volume required was 180 mls, then you would take 60 mls of your 60 mM NaCl solution and mix it with 120 mls of water.
WHY??
Because, if you divided 180 mls into three 'parts', each 'part' would be 60 mls. You want to have one 'part' of your 60 mM NaCl solution with two 'parts' of water, i.e. 60 mls of your 60 mM NaCl solution with 60 + 60 = 120 mls water.
What concentration of NaCl will you have after doing this dilution??
Well, you have diluted your 60 mM NaCl solution three times, so you will have a 60/3 = 20 mM solution after doing the dilution.
A 1:2 dilution is sometimes called a 'three-fold dilution' seeing as you are diluting something three times (your final volume will be three times more than your starting volume)... a 1:3 dilution is sometimes called a 'four-fold dilution' seeing as you are diluting something four times (your final volume will be four times more than your starting volume)...
I hope that helps you out
Sometimes, dilutions are talked about in terms of ratios. i.e. a 1:2 dilution or a 1:3 dilution.
Remember that ratios tell you how much of one thing there is in comparison to another thing.
So, for a 1:2 dilution (which could also be written as a '1 to 2 dilution'), this means that there will be one 'part' of one thing and two 'parts' of a second thing, and therefore three 'parts' in total.
Example:
If you were asked to make a 1:2 dilution of a 60 mM NaCl solution, and the final volume required was 180 mls, then you would take 60 mls of your 60 mM NaCl solution and mix it with 120 mls of water.
WHY??
Because, if you divided 180 mls into three 'parts', each 'part' would be 60 mls. You want to have one 'part' of your 60 mM NaCl solution with two 'parts' of water, i.e. 60 mls of your 60 mM NaCl solution with 60 + 60 = 120 mls water.
What concentration of NaCl will you have after doing this dilution??
Well, you have diluted your 60 mM NaCl solution three times, so you will have a 60/3 = 20 mM solution after doing the dilution.
A 1:2 dilution is sometimes called a 'three-fold dilution' seeing as you are diluting something three times (your final volume will be three times more than your starting volume)... a 1:3 dilution is sometimes called a 'four-fold dilution' seeing as you are diluting something four times (your final volume will be four times more than your starting volume)...
I hope that helps you out
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