Re: Looking for a method of detecting/measuring ethanol in fermenting solutions

On Jun 13, 10:35 pm, Thiophilus <thiophi...@xxxxxxxxxxxxxxx> wrote:
On Wed, 13 Jun 2007 14:34:12 -0700, Evan <crawling.ch...@xxxxxxxxx>
wrote:





Hi all, coming from an electronics/engineering background so I
apologize if there's an easy answer to this, I haven't come across it
yet...

I'm interested in being able to sense/measure alcohol fermentations in
a hobby situation, say home brewing or winemaking, where normally one
would have to open the vessel and take samples in order to see
specific gravity via floating hydrometer or hand held refractometer.
There are a number of problems involved, one being tha the solution of
course is not just alcohol and water, there are many other chemicals
present, as well as sediment, yeast and other things that impinge upon
clarity (Which I think would preclude the near-IR sensor that I saw
someone mention in this group's archives)

I have not seen any comercially available sensor that measures ethanol
in solution directly; i was thinking perhaps capacitance or resistance
could reliably be an indicator, but as I mentioned before there are
acids among other things present which I'm sure would render that kind
of reading useless.

The only thing resembling a lead I have is using infrared to observe
the CO2 bubbles leaving the air-trap on top of the sealed vessel; if I
could get a reasonable estimate of the volume per bubble I think I
could work backwards through fermentation chemical formulas to arrive
at the portion of alcohol being produced. Now i'm wondering if I
could find some sort of sensor that does ethanol vapor (e.g., a
breathalyzer type sensor) and expose it to the CO2 exhaust from the
fermentation and get a reliable reading there, then i would just have
to make some correlation between the reading in the vapor and what is
in the emitting solution.

Any thoughts would be greatly appreciated; I'm sure there's a good way
to do this, just have to find it...


Instead of counting bubbles, can you determine the volume of CO2
evolved per unit time somehow? An inverted graduated cylinder filled
with water, like in this picture:

http://www.chemheritage.org/EducationalServices/faces/env/activity/catalysi.htm

Or something as sophisticated as a gas flow meter.

Just keep in mind that if you have other microbes present, you may
have gas evolved from methane, too... (or is this really meant for
beer/wine consumption?)

Michael

.

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