Calculation/measurement of concentration

[Pelson]

Hi there,

My first post here, but hopefully not my last.

I have a little question in how you can accurately measure or calculate the ABV of your alcohol.
I have a densimeter, but I really want to know the exact concentration of the alcohol I distilled.

By measuring the density (I took 10mL with a pipet, and weighted it on a little scale) I came to a density of 0.82 g/mL.
By way of a data chart I found on internet (http://www.separationprocesses.com/Cour ... erty01.htm) I guessed a wt% of about 89%.

But as ethanol-water isn't an ideal mixture, how can I calculate the vol% of it?

I tried several websites to maybe get partial molar volumes, or calculate them myself, but I can't seem to find the right way to do so.
I study chemistry, so actually I should be able to know the answer, but still... (maybe I should've payed more attention in class in stead of drawing stills).

Thanks for any tips.