> You cannot measure the entropy, only changes of entropy

You can measure the changes in entropy from a minimal state and integrate - and you'll get the "total" entropy.

And thanks for looking it up! I remembered a very similar conversation and was wondering if you were the same person, but was a bit lazy to search :)

> You can measure the changes in entropy from a minimal state and integrate - and you'll get the "total" entropy

That doesn’t help with the following (at least if you keep those kinds of gas in gas state):

> if I give you three containers […] you can measure their entropy using thermodynamic experiments and tell which of the three is a mix of the other two because it will have a higher entropy

But you can weight them, it’s much easier.