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Mixing ethanol and water

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As most people know, if we mix ethanol and water, we don't end up with the sum of the parts in volume.

For example, if we mix:

50 litres ethanol
50 litres water

We end up with 96 litres. Not 100.

My question is this:

With the decrease in volume, we don't lose any mass of ethanol, so has the ABV increased?
i.e. is the ABV 50% or has it increased?

I'm trying to do some cost analysis of the total loss of ethanol throughout the distilling process to fully cost a micro distillery.

I've already got some pretty accurate figures on how much I will lose in the actual distilling stage, i.e. recovering the ethanol from heads and tails.

In the UK I need to pay for duty up front (initially) and so my ethanol is around £30 / $39 per litre.

I don't have access to 96% NGS yet to actually try this.

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@Welshbrew You are correct.  At 20°C  50 L of pure ethanol plus 50 L of pure water makes 96.46 L of spirit and your ABV would be ( (50 / 96.46) x 100) = 51.83%

But (unfortunately) you have not gained any ethanol and if you could distill it out again you would get the same 50 L of pure ethanol back, as well as the 50L of water.  Of course this is not possible because of the azeotrope, but I'm sure you get my drift.

The ABV definition is actually very useful, because if you started with 50 L of pure ethanol then no matter how you diluted it and irrespective of the shrinkage that occurs (which is different at different dilutions) you will always have your 50 L of pure ethanol in there somewhere and that is the bit that the Tax people want to know about.

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50 minutes ago, indyspirits said:

Although @meerkat won't suggest it, I will. Go buy a copy of alcodens to simplify your life.  I honestly think it's the best money we've spent. 

+1. when you add up how much time it saves, it pays for itself pretty quickly. At the very least, try the free trial

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57 minutes ago, Welshbrew said:

Funny you should say that. I downloaded it a few days ago.

Don't understand it yet, though. ?

If you need any help I am only too happy to guide you through a few calculations until your confidence builds.  The learning curve is a bit steep, but quite short and you will quickly master it.  The program is designed for speed and power and just like a powerful sports car, the effort of learning to drive it reaps the rewards.

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