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Hydrometer for Alcohol

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Martin King

Sat Feb 05 2011, 07:02PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

I need to check for contamination (specifically water) in various types of Alcohol. Quick tests with a brewing and a battery hydrometer have revealed that if I use a float type hydrometer then it will have to be made for the job. Does anyone know of any more sensitive (maybe electronic) ways of testing the relative density of alcohol?

Cheers.
Martin.

Bored Chemist

Sat Feb 05 2011, 07:28PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

There's this sort of thing

if you have a decent balance.
Measuring density will only assay the purity of the alcohol if there is nothing but water and alcohol present.

Martin King

Sat Feb 05 2011, 08:35PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Thanks water is the main concern I had some surprisingly good results simply by weighing various mixtures of Alcohol and water on some cheap Chinese scales although I only measured contamination in 20% increments. While doing it I was wondering how to get more accurately repeatable samples of small quantities of liquid and it looks like the Pycnometer is the answer to that question. Something like a probe that could be dunked in the alcohol and give a direct electronic readout would be our ideal solution (It doesn't have to work on density, I just thought that would be the easiest way?).

Cheers.
Martin.

Ash Small

Sat Feb 05 2011, 09:02PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Mixing with gunpowder and lighting it will tell you if it is 100% proof.

Martin King

Sat Feb 05 2011, 09:16PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Unfortunately 100 proof (note no %) is only about 50% alcohol (technically it's closer to 57%). A Mixture of 60% Water and 40% Isopropanol will still burn but is nowhere near pure enough for our purposes (need >90% ideally)

Martin.

Martin King

Sun Feb 06 2011, 12:50AM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Found this

"Principle of Operation

The submersible probe head contains a mathematically characterized spring-float system. When the head is immersed vertically in the liquid, the float moves vertically and the position of the float controls the position of a permanent magnet whose displacement is sensed by a concentric array of Hall-effect linear displacement sensors. The output signals of the sensors are mixed in a dedicated electronics module that provides an single output voltage whose magnitude is a direct linear measure of the quantity to be measured."

I guess it is liquid volume independent as the harder the liquid pushes the float up, the more the spring will resist so there is an equilibrium point that varies with the density of the liquid? Does that sound sensible?

Martin.

James

Sun Feb 06 2011, 01:01AM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

How about fractional distillation of a sample? I remember doing that back in school about... jeez, almost 20 years ago, but it wasn't very complicated. Vessel with the sample and a thermometer, condensing tube into a collection chamber. Heat the sample and the temperature will rise and plateau at the boiling point of the first substance, then when that is gone it will start to rise again to that of the second substance. If you stop as soon as it starts to rise again, virtually all of the alcohol ought to be in the collection vessel and the water left behind.

Wolfram

Sun Feb 06 2011, 01:02AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Martin King wrote ...

I need to check for contamination (specifically water) in various types of Alcohol. Quick tests with a brewing and a battery hydrometer have revealed that if I use a float type hydrometer then it will have to be made for the job. Does anyone know of any more sensitive (maybe electronic) ways of testing the relative density of alcohol?

Cheers.
Martin.

The hydrometers that you used, were they the kind made for measuring brew (usually marked in density relative to pure water) or the kind for measuring alcohol-water mixtures (usually marked in percent)? If it was the first kind, I understand why it didn't work too well. Both kinds are usually available in brewing stores, at least here where home distilling is relatively common. They are usually called spirit hydrometers, and they are usually marked from 0-100 percent. Here's

a random UK store I found that's selling them.

Martin King

Sun Feb 06 2011, 01:08AM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

James wrote ...

How about fractional distillation of a sample?

Thanks for the suggestion but WAY to much time required to carry out the test.

Martin.

Martin King

Sun Feb 06 2011, 01:28AM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Anders M. wrote ...

at least here where home distilling is relatively common. They are usually called spirit hydrometers, and they are usually marked from 0-100 percent. Here's

a random UK store I found that's selling them.

AH thanks! Yes standard brewing hydrometers are no good. Home distilling is illegal here (without a licence) hence lack of knowledge of spirit hydrometers

I've ordered a couple along with a cheap pycnometer

to do some further tests with. The spirit hydrometer would be a better bet if it works as it's a single step solution

Martin.

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