An aside:
The proportion in the head-space of a compound are not the same as the formula proportions
At this stage it is good to emphasize that the student’s description applies to smell (“head space”) of the fragrance and not the percentage composition in the formula. The percentage of fragrance materials necessary in the formula to achieve this “head-space” are determined by factor of vapour pressure, attraction between the molecules within the fragrance itself and the substrate that is being evaluated on (e.g. smelling blotter).
The measure that we use in this systems to replace these factor is the relative impact of the material (which takes in these aspects in a generalized form)
In essence the proportion necessary in a compound to produce lets say 10% of a low impact material in the head-space will need to be much higher than 10%
In contrast a high impact material it would need to be considerably less than 10% in the compound.
The following simplified formula is offered to approximate the adjustment that necessary for each material to ensure that the proportion in the compound is about right to give the target head space proportion required.