I doubt it because if you have cough medicine with codeine, the codeine is likely mixed throughout the syrup and doesn't float on top. I also wouldn't snort codeine because it has a high bioavailability anyways (when you take it orally the first pass through the liver will not result in much loss of the drug unlike with morphine).
I'd guesstimate 40-60mg of codeine as a decent dosage for somebody with no opiate tolerance and the only way to measure that dose is to look at the lable and see exactly how much codeine/ml and how many milliliters the bottle contains.