Re: test: absolute alcohol vs 95%

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From:James Hall <>
To:a i d a n s c h u r r <>,
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I developed a simple test for detecting the percentage of water in alcohol
some time ago utilising the fact that water and xylene are not miscible and
that xylene turns turbid or milky in the presence of water.  The addition
of dilute alcohol to xylene produced a milky appearance and by continuing
to add the dilute alcohol the water was re-absorbed leaving a clear fluid.
Not wishing to rely on a hydrometer, I found that by adding known dilutions
of alcohol, drop by drop, to a fixed volume of xylene, counting the number
of drops to initially turn the xylene turbid and  continuing  to record the
number of drops required to render the mixture clear again, a reproducible
estimation of the percentage of water in alcohol could be obtained.  The
test, however, was unable to detect water in 99% and 98% alcohol.  In your
case I would use a hydrometer to give you a quick result but if you do not
have a hydrometer then add 5 mls of xylene to a small beaker and place the
beaker on a black background.  Using a standard plastic dropper pipette
start adding your suspect alcohol, drop by drop, to the xylene keeping a
close watch for the appearance of any milkiness.  Make a note of the numbr
of drops it takes to turn the xylene milky.  Continue adding your suspect
alcohol until the milkiness disappears.  Typical results I obtain are:

97% alcohol--------4 drops to turn milky------8 drops to turn it clear
96% alcohol--------3 drops to turn milky------15 drops to turn it clear
95% alcohol--------3 drops to turn milky------37 drops to turn it clear
etc etc.

Best regards,

At 11:49 14/02/00 +1300, a i d a n s c h u r r wrote:
>Hi there all,
>We store 20L at a time of AA, 95% and xylene within the lab in 
>xplosafe containers.  These are filled from 200L drums in our 
>dangerous goods store by the orderlies.  It appears as if they may 
>have interposed the 95% for AA and vice versa at last filling (milky 
>xylene when dehydrating).  Does anyone know of a quick, 
>conclusive test to tell which is which?
>Thanks in advance,
>Aidan Schurr, New Zealand.
>a i d a n   c   s c h u r r 
>     mlso,  histology department
>      hutt valley health
>       lower hutt, new zealand
>     ph.  ++64 4 5709173
>     fax  ++64 4 5709214
Jim Hall,
MDA Equipment Evaluator,
Department of Histopathology,
University College London Hospitals,
Rockefeller Building,
University Street,
London, WC1E 6JJ.
Tel.No. 0171 209 6042
Fax 0171 387 3674

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