percentage question help please

[spudorange]

Hi,
Can not see a "introduce yourself" so just to say hello first.
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My problem is I need to very accurately (hopefully with a spreadsheet formula) calculate dilutions which have to be very very accurate.

I have been tasked with working out accurately some conversion rates of pure nicotine which is a fraction over 99% pure (990mg I believe)

Ideally in Excel I would enter say 50ml of dilutant and have it return the correct amount of nicotine in ml for say 72mg and be given for example 3ml

So on the first line it would have the figure to return 72mg dilution.
On the next it would have the figure for returning 36mg
On the next it would have the figure for returning 18mg
On the next it would have the figure for returning 12mg


I have managed to sort of get as far as the following, please advise if wrong.

I know for example 18ml of it + 982ml of dilution would get me a 90.0mg (approx 1 to 9 ratio)
and that the following figures may be correct, percentage wise though I need it in ml not as a % and 100% accurate.

12mg = 98.79% to 1.21% nicotine
18mg = 98.18% to 1.82% nicotine
72mg = 92.73% to 7.27% nicotine
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Edit: assuming the above figures is true then I think I may have answered it the long way round.

100ml base mixed to 72mg strength needs 7.27ml (1 litre needs 72.7ml)
100ml of base mixed to 18mg strength needs 1.82ml (1 litre needs 18.2ml)

so it would appear to be straightforward, if I need 10mg strength then I need .1ml per 100ml
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Really appreciate help please

 

[stapel]

Is this a math homework question, or a real-life (that is, science lab) computation? If the latter, then you'll need to provide the specific assumptions in play, as real-life mixtures often do not work according to (massively simplified) math-homework methods.