[Histonet] Hydrometer questions

Rene J Buesa rjbuesa <@t> yahoo.com
Fri Jun 29 09:23:37 CDT 2012

When I (and others) wrote you about the "age of the LFB" I at least was referring to the age of the solution.
You write now that you are going to try a 1950 LFB and I am sure that you are referring to the powder.
As to powdered stains they are quite stable, but it will be nice to find out.
To your hydrometer question: they are very simple to use, you just place the instrument very delicately into the ethanol sol. contained on a cylinder and it will sink up to a mark on the stem corresponding to the ethanol concentration, BUT there are some precautins to take:
1- the density of ethanol (and of any liquid for that matter) varies with the temperature; to higher temperature less push of the liquid and if the temp. is high you will get a reading corresponding to a higher ethanol concentration that the real value.
2- the cylinder has to be wide enough, otherwise the stem may come close to the wall of the cylinder and give you also a false reading.
Your best solution is to prepare fresh ethanol sol. every time you need it and to do that you just calculate how much dist. water you need to add to your ethanol of KNOWN concentration.
Finally, if you get a hydrometer for ethanol it cannot be used for isopropyl alcohol, because each has a different density.
Hydrometers can be bought from Fisher or Thomas Adams (I think they still sell them!).
René J.

From: Tim Wheelock <twheelock <@t> mclean.harvard.edu>
To: histonet <@t> lists.utsouthwestern.edu 
Sent: Friday, June 29, 2012 10:08 AM
Subject: [Histonet] Hydrometer questions

Hi everyone:

I wanted to thank everyone who gave me advice regarding my Luxol Fast Blue problem.

First, I am going to compare using a very old LFB bottle (from the 1950s) and a new bottle.
Then I will stain some test slides for 2 hours and 24 hours at 60C.
(I am having my oven checked this morning by facilities).

To find out how much water is really in my 95% ethanol, I am assuming that I need a hydrometer.
(I will also be using it to measure the isopropanol concentrations on my tissue processor).

Is there a type of hydrometer that labs use for these purposes?
Where do you buy yours from?
Can the alcohol/water concentrations be read right off of the hydrometer, like temperature is from a thermometer, or do you need to use an equation.
I have never used a hydrometer before.

Thank you,

Tim Wheelock
Harvard Brain Bank
McLean Hospital
Belmont, MA

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