Ever since I learned what “reverse osmosis” is, I have hated that name. And the method of water purification would be much better called “pressurized filtration” or “high-pressure micro-filtration”.
See, the idea is really simple: in any aqueous solution (that is, a mixture of water and other stuff), the water molecules are probably the smallest parts. So if you have a filter with REALLY small holes, and try to force the solution through it, what you get out the other side should be pure water. Osmosis is the natural process by which the water will then try to go back through the holes, as it is trying to have an equal mix of gunk and water on both sides of the filter. “Reverse osmosis” in no way reverses osmosis, nor does is utilize some other cool osmosis-like natural process, it just uses brute force to overcome osmosis.
Calling that “reverse osmosis” is like calling the principle by which rockets lift the Space Shuttle “reverse gravity”. “Well, see, we are pushing really hard in the opposite direction, and thus causing things to move in the opposite direction compared to how gravity would naturally move them. Would you prefer we called it ‘opposite gravity’?”
No, I’d prefer you called it thrust.
Osmotic pressure is the pressure required to bring osmosis to a stop across a semi-permeable membrane. If you artificially Increase the pressure beyond that point, the process of osmosis reverses. It’s not really an entirely illogical way of describing what’s happening.
[Semi-hijack]Probably worthy of it’s own thread, these sort of unfortunate popular names for technical principles. Me, I’m kind of bemused about the reversal between terms antibiotic (technically means “anti-life”, as in kill everything including already doomed skin cells and any possible infecting agents) and disinfectant (technically, “stop the infection [already in progress]”).[/SH]