# Ethanol Water mixture viscosity

It is found that increasing composition of $Ethanol$ in $Ethanol$-$water$ mixture increases the viscosity of the mixture upto certain composition, but after that the viscosity begins to decrease again. I could not figure out any theoretical explanation to this phenomenon. Any help with theoretical reasons will be appreciated.

• Maybe because Ethanol-Water interactions are most effective at the point of highest viscosity. I guess this is related to partial molar volume in a mixture of ethanol and water which depends on the mole fraction of the components. – Apoorv Potnis Jan 24 '18 at 14:37
• Alcohol water mixtures have v. unusual behaviour, probably not fully understood. At different compositions but with the same viscosity molecular properties are different as measured by probe molecules having different rotational diffusion times. The reason was rationalised as their being large clusters of ethanol or large ones of water depending on composition. Not what one would expect. – porphyrin Jan 24 '18 at 17:16
• That's a homework question, isn't it? Please write what behaviour you would expect (e.g. for a simpler mixture), and why. – Karl Jan 24 '18 at 19:35