Why mannitol solution 0.05% has opalescence？how to delete it?

[tzhisun]

when i add mannitol into water, the solution has opalescence. Does the solution forms colloid? Then how should I do to delete it? Thank you very much...

 

[phildukephd]

Look in a reference source for the solubility of mannitol in distilled water. If it is greater than 0.05% an impurity may be causing the opalescence. If so try filtration to remove it, or gentle heating to precipitate it. Purification by crystallization or chromatography may be in order. What does the supplier say about the purity?

 

[tzhisun]

Look in a reference source for the solubility of mannitol in distilled water. If it is greater than 0.05% an impurity may be causing the opalescence. If so try filtration to remove it, or gentle heating to precipitate it. Purification by crystallization or chromatography may be in order. What does the supplier say about the purity?

thanks so much! I think the purity has no problem. it's from Roquette. what puzzles me is that why does the phenomenon should happen while the concentration is much lower than its solubility. And the method you provide helps me a lot.

 

[phildukephd]

Opalescence usually is due to particles large enough to reflect light, possibly a colloidal solution. If so remove the colloid by filtration, centrifugation, precipitation, etc., make sure your distilled water is pure. Since mannitol is very water soluble, the opalescence is likely due to an impurity, or conceivably a stabilizing agent keeping some mannitol in the colloidal state. The supplier should give info on purity. If necessary purify by recrystallization, chromatography, etc. Good luck.