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Hydrometer for Alcohol

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Proud Mary

Sun Feb 06 2011, 11:32AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Martin King wrote ...

I need to check for contamination (specifically water) in various types of Alcohol.

If this is to be your specification, then the suggestions made so far may not be of much practical use.

You must first specify the alcohols to be tested, since the anhydrous forms of each will all have their own apparent specific gravity relative to pure water.

You should also specify the anticipated range of contamination. The procedures needed for accurately quantifying aqueous contamination below - for example only - 1% by volume, will be of a different character to those needed for estimating contamination - dilution - in the range 5% to 95% to the nearest 5%.

Martin King

Mon Feb 07 2011, 02:29PM

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

Thanks, the main alcohol to be tested is isopropanol, it's density is VERY close to ethanol so a spirit hydrometer should be OK for our purposes. We need to check for water contamination of greater than 5 or 10% (not sure yet what the acceptable limit is) we know that 20% is unusable. I should have the hydrometers sometime this week they were cheap enough to try, if they are no good then it's back to the drawing board.

Martin.

klugesmith

Mon Feb 07 2011, 11:15PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

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.

Yes, you need a hydrometer made for the specific gravity range between alcohol and water.
By "made for the job" do you mean it's not a common catalog item?
Then you're looking in the wrong catalogs. Search google or ebay for alcohol hydrometer.
[edit] Oops, sorry, I see that's already been addressed!

I first used one at the age of 9, when my family lived at an oil-pipeline outpost in Saudi Arabia (a legally dry country). When Dad's sugar water fermentation was ready, he borrowed a stainless-steel still from the maintenance shop. My job was to log the time, boiling temperature, and specific gravity as each jar-full distilled over. The first jar twice-distilled served as fuel for my chemistry-set spirit lamp.
Oh, as for starting with plain sugar -- to the neutral spirits product, apparently they added a concentrate to impart the color and flavor of various beverages. Probably no Glenlivet!

Proud Mary

Tue Feb 08 2011, 04:00PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Martin King wrote ...

Thanks, the main alcohol to be tested is isopropanol, it's density is VERY close to ethanol so a spirit hydrometer should be OK for our purposes. We need to check for water contamination of greater than 5 or 10% (not sure yet what the acceptable limit is) we know that 20% is unusable. I should have the hydrometers sometime this week they were cheap enough to try, if they are no good then it's back to the drawing board.

Martin King

Tue Feb 08 2011, 04:35PM

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

Thanks, although I suspect a freezer that goes down low enough isn't going to be cheap! The hydrometers arrived today (although one was broken

) so I'll try the SG method this evening.

Martin.

GluD

Tue Feb 08 2011, 05:16PM

Registered Member #1221 Joined: Wed Jan 09 2008, 06:17PM
Location: Odense, Denmark
Posts: 196

You dont need a freezer if you have access to dry ice and acetone. I think a well made ice bath with those two should be able to reach somewhere around -70*C.

klugesmith

Tue Feb 08 2011, 07:11PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

GluD wrote ...

You dont need a freezer if you have access to dry ice and acetone. I think a well made ice bath with those two should be able to reach somewhere around -70*C.

The equilibrium temperature of dry ice at 1 atm is -78C = 195K.
Not cold enough to freeze acetone (MP -95C = 178K)
or even pure isopropanol (MP -89C = 184K),
both of which are used in cooling baths.

But maybe it could freeze out a water-rich fraction from wet isopropanol
and leave a water-poor liquid phase.
Who here is an expert in melting and boiling of mixtures?

GluD

Tue Feb 08 2011, 08:20PM

Registered Member #1221 Joined: Wed Jan 09 2008, 06:17PM
Location: Odense, Denmark
Posts: 196

Hello Klugesmith

I dont think you have to freeze either the acetone nor the isopropanol.

If the solution is still liquid in a cooling bath with a temperature of -78*C, the solution should be pure enough to statisfy the demand for less then 10% water (it would freeze if there was 10% or more water). Or have I missed something?

Of course it would not reveal the exact concentration of the solution but I'm not sure if that is necessary or not.

And no I'm sadly not an expert in melting and boiling of mixtures, I'm just trying to help with what little knowledge I have...
It was just a suggestion if he had access to dry ice and acetone then I suppose it would be a quick and cheap way to check if it is more or less than 10% water.

Ash Small

Tue Feb 08 2011, 09:04PM

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

Apparently liquid nitrogen is quite easy to obtain. If the samples to be analysed are small you won't need a lot to cool them.

Obviously other factors have to be considered, but this would provide accurate results.

Martin King

Tue Feb 08 2011, 11:26PM

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

Well the spirit hydrometer is fine and a lot more sensitive than I thought it would be. It easily resolves 1% between 90 and 100% and the markings are far enough apart to guestimate to 0.5%. It also comes with a temperature compensation chart although I'm going to be doing relative measurements between a known good sample and the test sample so calibration/compensation is a bit less important.

Martin.

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