NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/sci/physics/fusion/1839

Internet Message Format | 1992-07-26 | 8.5 KB

Path: sparky!uunet!cs.utexas.edu!sun-barr!ames!agate!rsoft!mindlink!a752
From: [e-mail] (Bruce Dunn)
Newsgroups: sci.physics.fusion
Subject: Measuring D2O2 in LiOD electrolytes
Message-ID: <[e-mail]>
Date: 27 Jul 92 03:49:44 GMT
Organization: MIND LINK! - British Columbia, Canada
Distribution: world
Lines: 160

Measurement of D2O2 in saturated LiOD solutions


Background:
      There has been some suspicion that some of the thermal effects seen in
cold fusion cells may be related to the formation and later decomposition of
deuterium peroxide.  This note describes a chemical assay for hydrogen peroxide
which I have designed for testing very small samples of saturated LiOH.  It
presumably would work as well for deuterium peroxide in LiOD.  I developed and
fine-tuned the assay based on some previous work that I had done measuring
peroxide in solution.  The assay has been tested with known peroxide
concentrations and saturated LiOH, and has a sensitivity of at least 10E-4
molar (0.0001 molar).

Principle:
        Hydrogen peroxide oxidizes iodide ion (I-) to iodine (I2).  In a
solution with excess iodide, the resultant iodine forms a complex with iodide
to give the ion I3-.  The I3- is visualized by adding starch to the solution,
which forms a blue complex with the I3-.  The peroxide oxidation of I- to I3-
is relatively slow, so to speed up the reaction molybdate ion is added to the
solution - the molybdate acts as a catalyst.  The color does not appear at
alkaline pH, so the assay is performed in an acidic acetate buffer.

Reagents:

Hydrogen Peroxide
        Drugstore 3% Hydrogen Peroxide (sometimes called 10 volume).  The
bottle that I purchased was marked "3% w/v" which I take to be weight/volume,
or 30 grams peroxide per liter.  The Merck index suggests that nominal "3%"
material ranges in strength from 2.5 to 3.5 %.  For the purposes of a standard
for a semiquantitative assay, the peroxide is assumed to be 3% by weight, which
is 0.88 molar.  Be sure to use freshly bought peroxide, as it is unstable in
long term storage.  If accurately calibrated standards of peroxide are needed,
the peroxide concentration of solutions can be measured by ultraviolet
spectrophotometry.  I am sorry, but I don't have the wavelength or extinction
coefficient handy - if anyone has this information, would they please post it.

        From this material, prepare a series of standards by dilution in water.
I prepared standards as follows:

10E-1 molar = 10 ml of stock peroxide plus 78 ml of water for a total of 88 ml
10E-2 molar = 10 ml of 10E-1 M plus 90 ml water for a total of 100 ml
10E-3 molar = 10 ml of 10E-2 M plus 90 ml water for a total of 100 ml
10E-4 molar = 10 ml of 10E-3 M plus 90 ml water for a total of 100 ml
10E-5 molar = 10 ml of 10E-4 M plus 90 ml water for a total of 100 ml

        For the sake of clarity, note that in the notation that I am using,
10E-3 molar peroxide is 1 millimolar peroxide.

        Any other logical scheme could be used, depending on the glassware etc.
available.

Potassium Iodide, KI  :  MW 166  - sodium iodide would probably work as well

Ammonium Molybdate, (NH4)6Mo7O24.4H2O : MW 1236  - probably any other molybdate
salt would work

Acetic Acid:    glacial acetic acid

Starch:         Liquid Laundry Starch:  I bought a $2 bottle of "Glide Fabric
Starch" at my local grocery store.  The starch is a viscous, somewhat cloudy
liquid with a very faint blue tinge.


Color Reagent (prepare fresh each day):

1) weigh 166 mg of Potassium Iodide and 12 mg of Ammonium Molybdate, and
dissolve in 24 ml water
2) add 25 ml glacial acetic acid
3) add 1 ml liquid starch

This produces a reagent containing:

2x10E-2 molar Potassium Iodide - this concentration is not critical within a
factor of approximately 2 or 3 fold

2x10E-4 molar Ammonium Molybdate - this concentration is not critical within a
factor of approximately 10 fold

50% acetic acid  - this concentration is not critical, but must be high enough
to over-neutralize any base added to it

2% liquid starch - this concentration is not critical within a factor of
approximately 2 or 3 fold

The concentrations used were determined in a series of trials using 10E-3 molar
peroxide, and aiming for the maximum color development.  If someone wants to
further develop the assay, it would be appropriate to use a 10E-4 M peroxide
standard, and vary the iodide and starch concentration for maximum color.  The
molybdate is catalytic, and it's concentration hardly affects the final color -
if the molybdate however is left out, little or no color develops.  If either
too much starch or too much iodide is used, the color is less intense and tend
to be a golden brown rather than blue

The assay is performed by adding together 1 volume of the LiOD, 1 volume of
color reagent, and 1 volume of either water or hydrogen peroxide standard.

Assay blank:                    1 volume color reagent and 2 volumes water

Experimental determination:     1 volume color reagent, 1  volume LiOD,
                                1 volume water

Positive Control:               1 volume color reagent, 1 volume LiOH,
                                1 volume peroxide standard

Note that saturated LiOD will be somewhere around 5 molar (one reference book
lists the solubility of LiOH as 128 grams/liter at 20 degrees, or 5.34 molar).
The color reagent contains 50% acetic acid, which is just a little under 9
molar.  Equal volumes of LiOD and color reagent are added, with the LiOD
neutralizing about half the acid, and forming an acetate buffer in the mixture.

The volumes used can be varied depending on how much material is withdrawn from
the cell.  I performed my assays in very small plastic centrifuge tubes using
50 microliters (about 2 drops) of saturated LiOH (I am not in the cold fusion
business so don't have any LiOD), 50 microliters of color reagent, and 50
microliters of peroxide standard or water.  This could probably be scaled down
to 1 drop of each in the bottom of a tube or as a spot test on a piece of wax
paper or plastic.

Using 50 microliters of color reagent, 50 microliters of saturated LiOH, and 50
microliters of peroxide or water, I found that 10E-1 molar and 10E-2 molar
peroxide produced an almost instantaneous dark blue-black color.  10E-3 molar
peroxide produced a dark blue color, but took a couple of minutes.  10E-4 molar
peroxide over several minutes produced a yellow-brown color, clearly
distinguishable from the colorless solution produced by substituting water for
the peroxide.  10E-5 molar peroxide or water gave no visible color.

The assay as described is only semiquantitative, and has a detection limit of
at least 10E-4 molar.   Using standards of peroxide, I think the assay will be
good enough to put an upper limit of say 10E-4 molar on the deuterium peroxide
concentration in a 1 or 2 drop sample taken from a cell (ie. if you see no
color, but show using the same reagents that you can detect the peroxide in an
equivalent volume of 10E-4 molar hydrogen peroxide standard, then the LiOD has
to have less than the 10E-4 molar peroxide).

As an alternative to using starch for visualizing the I3-, it is possible to
measure the I3- at 360 nm in a spectrophotometer.  This would require that the
volumes be scaled up to give enough volume for a spectrophotometer cell.  Using
spectrophotometry at 360 nm would make the assay more quantitative and would
possibly boost the sensitivity by a factor of 10 or so (detection of 10E-5
molar peroxide or better).  If 360 nm absorbance is used, the provision of
appropriate blanks is important to avoid the possibility that 360 nm absorbance
comes from the reagents or impurities in the used LiOD.

        Peroxide is stated by reference books to be unstable in alkali, and a
trace of acid is often added to commercial peroxide as a stabilizer. I have
added 50 microliters of 10E-4 molar peroxide to 50 microliters of saturated
LiOH - after 10 minutes I added the acidic color reagent.  Assays performed in
the manner gave the same color intensity as did assays using peroxide which had
not been pre-incubated with LiOH.  This suggests that at least on a short term
basis, peroxide is stable enough to potentially accumulate with time in a LiOD
solution.

        I leave it to others to do the appropriate calculations to calculate
whether the detection limit of 10E-4 molar is adequate to rule out peroxide
effects in cells.  If not, I would be prepared to further fine tune the assay,
probably using larger volumes and spectrophotometry at 360 nm.

--
Bruce Dunn    Vancouver, Canada   [e-mail]