[jane doe]

Does water dissolve more substances than any other solute? I've seen this claim online on multiple sites, but I've never found it in a credible source.

[wildfyr]

This is borderline impossible to quantify. The possible combinations of molecules with just 30 or so atoms is more than the number of atoms in the universe. Breaking this down by solubility is beyond our abilities. It's a good solvent, but in the realm of everyday bench science, DMF or DMSO is probably more universal.

[Arkcon]

Its a cute maxim, meant more to induce wide-eyed wonder, than it is a useful description.

"everything dissolves in water, even glass, even rock even crude petroleum.  Water is magic!"

Ahem.

Enough glass dissolves in water to adversely affect very delicate analytical needs.  Wave action does weather Earth's rocks.  Bacterial action and wave motion eventually disperse oil spills, after much ecological damage.  But these are only gee-wiz examples.

Its a bit of a problem, when a High School chemistry student is told "like dissolves like", then they get to university, and their HPLC grade water has become contaminated by detectable levels of solvent, simply because the bottle was open to the air for a while.  Its just stuff that happens.