Perhaps. But at least one complexity there is that there are a couple of isotopes (of different mass) for both oxygen and hydrogen.
There's the Vienna Standard Mean Ocean Water[1][2] which accounts for differing isotopic compositions in different parts of the world.
There's been some competing attempts to the Standard Kilogram, including a pure silicon sphere of extremely precise physical dimensions (which we're good at), and using the lattice spacing to determine the number of atoms.
There's the Vienna Standard Mean Ocean Water[1][2] which accounts for differing isotopic compositions in different parts of the world.
There's been some competing attempts to the Standard Kilogram, including a pure silicon sphere of extremely precise physical dimensions (which we're good at), and using the lattice spacing to determine the number of atoms.
See the Avagadro Project[3]
[1] https://en.wikipedia.org/wiki/Vienna_Standard_Mean_Ocean_Wat...
[2] The "Ocean" bit doesn't mean what you might expect. It's still fresh (non-saline) water.
[3] https://en.wikipedia.org/wiki/Avogadro_project#Avogadro_proj...