As far as I understand, a dispersion of particles is equivalent to a true solution in what respect to the osmotic phenomenon. This was demonstrated by Einstein. There appear to be several examples in the literature of such behavior using colloids. We are using egg membranes to carry on some simple, high-school grade, exploratory experiments on Osmosis. However, after spotting some inconsistencies on Internet regarding substances osmotically active and non active, I decided to test a suspension of 93-nm polystyrene particle. This particles are subject to Brownian motion. We did not observe any measurable osmotic effect after three weeks. This can possibly be related to the dilute concentration used. In contrast, a 10 to 20 mm change in the original height of the liquids in the containers was observed when using pure water and a saturated NaCl solution. Hence, despite the well known independence of Colligative properites on the structure of the molecules dissolved, I wonder, if in the case of suspensions there are other further requirements, or if there is new evidence regarding non polar molecules that I am not aware of.