Distillation is a physical process (some say chemical, but chemistry is just a subset of physics anyways. No chemicals are involved (thats why I'd rather say physical). Water is separated from its other components via boiling. I've done this in countless chemistry labs although no chemicals are used, just heat.

Osmosis occurs when different concentrations of solvents occurs in a fluid like water and the water will "move around" to create a homogeneous solution or in other words have the same concentration throughout.

Reverse osmosis is a technique to pull solvents through a filter, such as activated carbon which is semipermeable and blah blah blah.

Anyways, I don't understand the question or rather, statement.

Distilled is better? For a cooling loop, there will be virtually NO difference in the heat absorption properties. In a medical lab setting, distilled water is never used, only DI water. Usually, a super mediquell (super b/c it works faster, NOT higher quality) filter is used to produce what is considered the purest water in the world. The only thing better would be to autoclave it. But anyways, I'm getting slightly

The purity in a RO filter is limited by the size of the impurity it can filter as well as the type of filter, such as activated carbon. Distilled is not limited by particle size, only boiling point. If there are no other liquids in the water, just solvents, incredibly pure water can be extracted.

I'm guessing that the point of this topic is which is type of water is better for a cooling loop, right? I have a triple reverse osmosis filter at home, but I need to changed the activated carbon, so I'm going w/ distilled to be safe. I am also not sure how well cations and anions are removed (calcium, etc) via RO. I wouldn't see it as an issue. Nikhsub1 has done this...

Just stick with distilled, its a better guarantee that nothing bad will happen in your loop due to impurities. I'm saying this only b/c I've never seen just RO water for sale. I know that bottle waters have it in there, but who knows exactly what else is added.

If you can say what properties you want us to test, I'm sure someone can come up with a chart. RO vs Distilled? That can go on indefinitely. We need context man!