RE: [Histonet] Gravimetric Factor Equation

From:"Connie McManus"

I have never bothered with gravimetry calculations, but it's always good
to know for times when you do notice a difference in the quality of
staining.  In my lab, a notebook is kept on everything we use ...
antibodies, stains, etc.  Things found on the bottle and or the data
sheet are entered into this log book along with the date received,
opened, etc.  So if ever we do encounter a problem with new dyes,
antibodies, whatever, we have a quick and easy reference.  The original
data sheets are also kept, but I find a log book easier to deal with.

Connie McManus
Utah Veterinary Diagnostics Laboratory
Utah State University
Logan, UT
Phone:  435/797-1891
fax: 435/797-2805

-----Original Message-----
[] On Behalf Of
Sent: Tuesday, June 15, 2004 2:59 AM
To: Dave;
Subject: Re: [Histonet] Gravimetric Factor Equation

Gravimeter factor =

(conc of present dye)
__________________            X    (grams of  old dye used.)
(concentration of new dye)

Let's say your present dye is 75% dye (meaning 25% salts, fillers,
impurities - things that won't color the dye, but are a by-product or
possible needed to make the correct charge). And the solution you have
making are working great. Now you buy a new bottle of the same dye. It's
concentration is 50% (meaning 50% salts, fillers, impurities, etc.).
Obviously, the new dye is much weaker, so in order for the new dye  to
as darkly as the old dye, hopefully it would make sense that MORE of the
dye is needed.

If the solution you are to make is a 2% solution, that's 2 grams in 100
of solvent (water, alcohol). (If the math doesn't show up right, make
screen of your email full size)

_____      X  (2 g) = (150) / (50) = 3 grams of new weaker dye are

Conversely, if the old dye was 75%, and the new dye is 95%, then the new
is more concentrated. So for the new stronger dye to stain as pale as
old dye, less of the new dye must be used.

_____     X  (2 g) = (150) / (95) = 1.58 grams of the new stronger dye

(Percent signs cancel themselves out, leaving the grams.)

Just to let you know, in our lab, we usually  don't pay attention to GF.
First of all, many of our dyes seem fairly consistent in percentage from
lot to another (87% vs 85% for example), so there isn't that big of a
in amount needed. Second, for example, if we are make up a 1% light
counterstain, we end up re-using it for 3-4 months. Therefore, by the
end of
4 months, it's no longer 1%, it is a much lower percent/much weaker
solution. What used to take 1-2 seconds to stain when it was freshly
up, now takes 30 seconds. As histotechs, we "eyeball" the quality of the
stained control (with or without the microscope), and adjust time
accordingly. And our procedures reflect that (stain in light green 2-30
seconds until background is pale).

But, yes, sometimes this can cause a problem (when the lot percentages
considerably) and adjustments are made. Someone puts a sign on the dye
bottle that says "Use 1.2 grams for every 1.0 grams needed", for

Hope this helps.

Peggy A. Wenk, HTL(ASCP)SLS
William Beaumont Hospital
Royal Oak, MI

----- Original Message -----
From: "Dave" 
Sent: Monday, June 14, 2004 12:11 PM
Subject: [Histonet] Gravimetric Factor Equation

In Freida Carson's book on histology, she has written to find the
gravimetric factor of a dye is   conc of present dye
                                                 conc of new dye

However study questions that I've been reviewing have the formula
I'm sure that Freida Carson is correct but I need to know for sure.  I
haven't had any luck on the internet and co workers don't have a clue
what I'm talking about.  Thanks in advance.

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