Help with osmolarity, tonicity, and the like..

Hello All,

I did a lab where we used sheep's blood to test tonicity/osmolarity in various solutions. The trend shows that if the osmolarity was above 284 it would appear cloudy accept for one of the solutions. The solution 5.02% Diacetin with osmolarity of 285 appeared clear. Now I'm not sure why this is. I also predicted that if tonicity affects % transmittance, then hypotonic solution would have a greater %. This prediction turned out to be true because when I put the Diacetin in the spectrophotometer, it had a much higher percent (88%) vs the 2.62% Glycerol solution with only 4.5%. So I just need someone to explain to me why the Diacetin solution turned out clear since the Osmolarity was above 284, and why when put in the spectrophotometer it confirmed that it should be a hypotonic solution.

Any ideas or possible explanations would be appreciated. Thank you.