I just started doing alchemy.
I made some
https://wiki.project1999.com/Vial_of_Tamed_Mercury
I tried to combine 10x together in a Bearskin Potion Bag, and the "You cannot combine these items in this container type!" message appeared.
https://wiki.project1999.com/10_Dose..._Tamed_Mercury
The 5x combine works - i tested that
https://wiki.project1999.com/5_Dose_..._Tamed_Mercury