Okey this is my thought. I have an espresso machine. On the side there is a thing you open once in a while to empty which contain solid compact powder of coffe residue. People have also used this to put in the earth together with plants to kill bugs, so appaerently it has caffeine. Compared to the caffeine transferred to the cup, does anybody know roughly how much caffeine it conatins?

 

Im thinking of either mix it with HCl to make caffeine.hcl salt or just subliming it in order to extract caffeine, will these methods work with the amount of caffeine present in the coffe residue?

the residue will be roughly the same conc as the cafeine in your drink, and the reason it`s put with plants is the Acidity of the grinds and simple organic mass, nothing at all to do with Cafeine

Ahaa. Coffe/tea plants contain caffeine as a pesticide so that's why i thought taht residue killed bugs.

 

But does caffeine react with HCl to form water-soluble Caffeine.HCl available for extraction by evaporation after filtrering away residue? Question is how many side products follow with that also crystallize when the water evaporates in the final step.

it will do when you have a purified Caffeine molecule, but of course Long before you get to That stage, you need to Extract it, something Non polar is ideal.

Methylene Chloride would be the Obvious/Idea choice