[mbckenny]

Hi,

I am trying to work out the % by volume of alcohol in wine from some refractive index data I collected.

Here's the data;

R.I of pure wine: 1.341
R.I of water 1.331
R.I of ethanol 1.359

I plotted a graph of refractive index vs mole fraction of ethanol (0 for water 1 for ethanol) and then using the line equation (I got y = 0.028 x + 1.331) I worked out the mole fraction of wine to be 0.3571.

My query is this...

Does this mean that the % by volume of alcohol in wine is 35.71% as this seems a bit high as I know the alcohol content to be around 13% or do I need to do further calculations with this data, or is my data rubbish.

Cheers,

Mike

[mbckenny]

I worked it out by doing the following equation;

(Density of ethanol/molecular mass) X Refractive index (of wine)
--------------------------------------------------------------
(density of water/molecular mass) X 1-refractive index (of wine)

That gave me the volume fraction which I then multiplied by 100 to give me an answer of 14.63% alcohol.

Cheers
Mike

[ryu daruin]

I worked it out by doing the following equation;

(Density of ethanol/molecular mass) X Refractive index (of wine)
--------------------------------------------------------------
(density of water/molecular mass) X 1-refractive index (of wine)

That gave me the volume fraction which I then multiplied by 100 to give me an answer of 14.63% alcohol.

Cheers
Mike

How did you work out the mole fraction of wine?