Optimum temp.

[dStill]

Hi All! I'm new to this, Its my second run and I'm hoping for some clarification on what the optimum temperature is.

First, My Rig.

Mine is a Nixen-Stone Offset head Reflux Still.
I designed it from Matts Offset head still as posted in the offset head still photo section.
I'm heating with propane, and the boiler is a 50 litre keg with a copper screw-on collar soldered to it.
I'm using A digital thermometer.

My Question is This.

Alcohol Vaporizes at 78 C.

The instructions on this site say to stop collecting at 82 C.

So if i collect at 79 C.-81C will the product be less pure?

Will the product more pure if i only collect at 78 C?

Or will it be totally Pure until i hit 82 C?

Thanks so much for any insight into this, i cant find an answer in the books i have, or on the internet.

[rad14701]

The product will never be totally pure... The purest that a Nixon Stone offset head reflux column will produce is ~95%... That goes for all but vacuum stills... See these charts for a better understanding of the temperature relationship of wash and distillate to purity...

[Hawke]

If your reflux still is working right, the temp should stay steady at around 79*C for 95% of the run. During the last 5% of the run, the temp will climb and ABV will drop quite rapidly.

[DrTorque]

As much as I love to watch temperatures on my thermocouples - I realize that it's not the best way to judge when I should make cuts. Test them first by putting them in boiling water and ice water. If you're off by just ONE degree, you're plan to make a cut between 81 and 82 degrees is going to waste a lot of good stuff or introduce unwanted stuff.

Use the temperature as a guide and a sanity check, but make your cuts by smell and taste.

[dStill]

Thanks guy's I think i understand much better now, (the graph was a big help) my still stabilizes at 78.5c-78.6c then starts to climb quickly at the end of the run. As I understand it, at that point the % of ethanol starts going down, so that's when i make my cut and save the rest for re-distillation. soon I'll make a way to measure % as i go along, that should help.

thanks for the info guy's!

[Hawke]

soon I'll make a way to measure % as i go along, that should help.

That's called a 'parrot's beak' or eprovette. Between a thermo and a parrot, you would have all the info you need. (except for the taste buds and sniffer)