From: ames!FNALD.FNAL.GOV!DROEGE
Subject: Starting a New Run
Reply-To: ames!FNALD.FNAL.GOV!DROEGE
Organization: Sci.physics.fusion/Mail Gateway
Date: Thu, 10 Sep 1992 00:43:02 GMT

As stated in the last message, we cleaned out cell 4A1 and put in the 
other ground cathode prepared by Cam Tibbals.  It is 1 cm x 2 cm x 1 mm.
Twice the size of the previous cathode which gives problems if we want 
to run at high current.  

First we calibrated several days with the cell removed and replaced with
a resistor.  Did some source in/out experiments with the resistor in the
calorimeter.  Looks like nothing to me, but we will later look at this 
data in the same way as the earlier data as a control.  

Next, the cell was filled and placed in the calorimeter with near zero 
cell voltage.  (Commanding zero cell current does not guarantee zero
cell voltage.)  We filled with 30 cc of the very saturated LiOD + D2O 
mixture used in the last run, plus an additional 3 cc of H2O.  Don't
ask why, this is exploration.

The calorimeter was closed up and run for seven hours at zero cell current.
We then started charging at 30 ma per sq cm.  Before the charging started 
the calorimeter had returned to the previous calibration - within about 
2 mw, but this is known to be luck.  We think good to 8 mw one sigma.  

At this low current density, it took about 5 hours for the Pd to stop 
absorbing H/D.  We backfilled this time with O2, making several cell changes.
Likely 90% or better O2.  So we are back to measuring absorption by excess
oxygen. 

For the best measurement of the heat of absorption, it would be desirable to
balance the calorimeter running reversed, then go to forward operation.  This 
makes the cell temperature about the same and reduces the thermal transient.
Because we are afraid that running backwards will somehow spoil (who knows
why!) the reaction, this run went from zero to charging current.

There is thus a problem in unscrambling what is going on when charging is
initiated.  It is possible we will be able to use the various thermometers
to calculate how much heat went into raising the temperature of the cell 
later.  

In any case, after an hour or so things are pretty much at steady state, and
indicated a heat of absorption of order 66 killojoules per mole D/H 
absorbed.  No worse than a 20% measurement now, likely to get to 5% when
I have applied all the corrections I know about.  

At 0.82 D/Pd ratio, the heat of absorption went through zero and turned 
negative.  We topped out at a D/Pd ratio of 0.92.  I give these ratios 
a 5% error limit at the moment.  Because a smaller fraction of the D is 
absorbed at the high loading, the error of measurement of the heat of 
absorption increases at high loading.  But it really did look like a reversal
at 0.82.

There is also a nice measurement of the %absorption versus D/Pd loading.  At
the start, my measurement indicated about 102% absorption.  Obviously cannot
be over 100% but it is likely that the catalyst took a while to get up to
100%.  Another reason for first operating reversed.  

I have a scheme for doing all this right if anyone cares.  Start out running
reversed to a third electrode, which is then kept at the most negative 
potential to keep from plating garbage on the the cathode.  Also use a 
much larger cathode.  

Somewhere, someone published good numbers here.  I have about 3 feet of 
stuff to go through to find the numbers.  Can someone who knows where they 
are put them up for me?  i.e. heat of absorption, and the loading where
it is supposed to reverse.

Tom Droege

P.S.  Another reason for indicating > 100% absorption at the start of the
run is that the cell is heating up.  All this can be worked on, but at the
moment I am still looking for "anomalous heat".  It looks like I could spend
a month just looking at this piece of data and doing the best possible job
of correction.  But I don't plan to do it unless someone really wants it.