Your first objection is not the case. The procedure I outlined used a 10 mL
volumetric pipette, not a flask, and a plain beaker. These are extremely
common in medical laboratories and accurate enough for the purpose.
Your second objection is quite true, but really, how difficult is it to make
one time alcohol dilutions and weigh them, then plot the concentrations against
either the weights or the specific gravity on a graph. For occasional use it
works extremely well. On the other hand, if you are doing it many times a day,
then a densitometer with direct readings of acohol concentrations should be
used.
Bryan Llewellyn
----- Original Message -----
From: Rene J Buesa
To: Bryan Llewellyn ; Amos Brooks
Cc: Histonet
Sent: Sunday, November 28, 2010 6:20 AM
Subject: Re: [Histonet] CHECKING ALCOHOL CONCENTRATIONS
Amos:
Bryan's method has 2 problems:
1- It requires a volumetric flask (one that assures a constant volume
and it does that because the glass cap has a small hole that allows overflow of
excess liquid), and
2- it will tell you the density of the liquid you placed inside the
flask but NOT its strength, in this case the amount of water the alcohol
contains. That would require a table to compare the density you calculated
against that of known alcoholic dilutions.
For the level of accuracy needed in tissue processing, any hydrometer
will suffice, and you don't have to shake it, just wipe it dry with a towel.
René J.
--- On Fri, 11/26/10, Amos Brooks <amosbro...@gmail.com> wrote:
From: Amos Brooks <amosbro...@gmail.com>
Subject: Re: [Histonet] CHECKING ALCOHOL CONCENTRATIONS
To: "Bryan Llewellyn" <llewl...@shaw.ca>
Cc: "Histonet" <histonet@lists.utsouthwestern.edu>
Date: Friday, November 26, 2010, 4:32 PM
Wow Bryan,
That's pretty slick. Obviously weighing it would do the trick I
hadn't
thought of that. I'll have to remember that the next time I
mindlessly try to
shake the excess liquid off my hydrometer and have it break in my
hands. Gosh
I hated that! That is definitely a great and probably more precise
way of
doing it.
Amos
On Thursday 25 November 2010 03:11:07 pm Bryan Llewellyn wrote:
> Specific gravity is mass/volume. In this context that is
grams/millilitre.
> It can easily be measured without a hydrometer.
>
> 1. Obtain a 10 ml beaker and weigh it to 2 decimal places.
> 2. Measure 10 mL of the alcohol with a volumetric pipette and
place in the
> beaker.
> 3. Reweigh the beaker with the alcohol in it, again to 2 decimal
places.
> 4. Subtract the weight of the beaker from the weight of the beaker
and
> alcohol, giving the weight of the alcohol
> 5. Divide the weight of the alcohol by 10 to get the SG to 3
decimal
> places.
>
> Bryan Llewellyn
>
>
> ----- Original Message -----
> From: "Amos Brooks" <amosbro...@gmail.com>
> To: <histonet@lists.utsouthwestern.edu>; <vickroy....@mhsil.com>
> Sent: Thursday, November 25, 2010 3:14 AM
> Subject: [Histonet] CHECKING ALCOHOL CONCENTRATIONS
>
>
> Hi Jim,
> Hydrometers can get really expensive. I searched around for
one with a
> good price and stumbled on this one from Cole Parmer (now Thermo
like
> everyone else in the world):
> Thermo Scientific ERTCO® Alcohol Hydrometer, 0 to 100% Tralle, 0 to
200
> Proof,
> Plain Form ... CAT# EW-08285-00
> I picked it up for $29.50, but that was with my University
discount. I'm
> not sure what regular price is or what discounts you might be able
to get.
> It sure
> beat the heck out of some of these $200 ones out there. This one
has both
> ETOH
> percentages as well as ETOH proofs. It works well for us.
>
> Happy Thanksgiving,
> Amos
>
>
> Message: 4
> Date: Tue, 23 Nov 2010 13:02:24 -0600
> From: "Vickroy, Jim" <vickroy....@mhsil.com>
> Subject: [Histonet] CHECKING ALCOHOL CONCENTRATIONS
> To: "histonet@lists.utsouthwestern.edu"
> <histonet@lists.utsouthwestern.edu>
> Message-ID:
> <24a4826e8ef0964d86bc5317306f58a55510fe3...@mmc-
> mail.ad.mhsil.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Does anyone know where we can purchase a hydrometer or other
instrument
for
> confirming alcohol percentages, such as 70, 85, 95, 100? We had a
mixup in
> chemicals on a processor and I am going to be asked about
instruments to
> confirm percentages before processing.
>
> Meeting with risk management tomorrow.
>
>
> James Vickroy BS, HT(ASCP)
>
> Surgical and Autopsy Pathology Technical Supervisor
> Memorial Medical Center
> 217-788-4046
>
> _______________________________________________
> Histonet mailing list
> Histonet@lists.utsouthwestern.edu
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