Yesterday I was lucky to see a friend of mine that teaches biochemistry, and I asked him about the solutions.
The thing is more complicated than it looks.
I also have read your blog.
He explained me that when saying 10% solution may mean three different things.
It may mean 10% w/v (weight to volume)
10% v/v (volume to volume)
or 10% w/w (weight to weight)
All of the above can be of totally different in potency!!
So a solution should be declared apart from its percentage to its type as well.
This is very important for us, as a solution 1%w/v of ethyl vanillin is more potent than a 1%solution v/v.
This information is very important to correctly recreate a formula, and I haven't really see this information in the bottles of the retailers we buy raw materials.
My intuition says that the perfumery industry works with w/w solutions but I don't really now.
Chris in your example with 2.5grams of EO in 25 grams ethanol, the solution you get is not 10%,
as the analogy is 1:10 and not 1:9. So it is slightly weaker than 10%.
If anyone has the information what type of solutions the industry is using that will be really helpful.
I guess this information would be on any bottle of Givaudan, but as an amateur I have never bought from Givaudan directly.