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Subject: pH meters

pH meters

From: Hilary A. Kaplan <libhk<-a>
Date: Wednesday, November 4, 1987
I have been researching pH meters recently because we are interested in
purchasing one for the Conservation facility at Emory.  I have contacted
a number of sources and unfortunately, no one I spoke with had recently
purchased a meter. Nancy Heugh, paper conservator at the HRHRC felt that
the Fischer model they have is overkill (it is capable of providing much
more information than is generally needed when wanting simply pH) and is
very temperamental and sensitive.  She felt that the Beckman model they
have though old, was perfectly good for just testing pH.  Marc Reeves at
NYPL has a Beckman that is also an old model and uses it everyday and is
quite happy with it.  His has a combination electrode.  Marc reminded me
that Beckman is really Corning.

I spoke with Connie McCabe at the National Archives and she recommended
not buying the cheapest meter.  She also feels that two electrodes, a
glass and a Calomel were more reliable than a combination electrode. She
finds that a combination electrode is more likely to cause problems and
is not as reliable.

I also spoke with someone at CAL (I think it was Mary Baker) who
recommended Corning and told me that Fischer does not make anything
themselves--it is likely Beckman.  Whoever it was at CAL also
recommended buying two electrodes rather than a combination electrode.

I eventually spoke with Dr. Shahani at LC who was very helpful.  He
listened to my purposes in purchasing the meter (slurries, some surface
readings) and several days later contacted me to say he thought that the
Beckman pHI #10 meter would serve my purposes well.  I have since
received literature on this particular model and have had a sales
representative demonstrate it.  It lists for $445 with startup kit and
until 30 December or thereabouts, there is an introductory offer for an
$85 stand that comes free.  The #10 comes with a combination (epoxy)
electrode suitable for slurriers.  #34104-970.  We will also likely
purchase a flat bulb combination electrode for surface readings, an
additional $98, #3 4105-054.  Beckman as well as VWR Scientific will
sell these models.

It has been necessary for me to consider the cost factor as well as
accuracy and reliability of any particular meter. My choice of a
combination electrode wa s greatly determined by costs.  Purchasing two
electrodes rather than a combination electrode essentially doubles the
amount you must spend--the cost of the additional electrode as well as
additional cables.  Also, I have selected epoxy rather than glass
(though glass may give a faster reading and be easier to clean) mostly
because the epoxy is more rugged and I will need to worry less about the
magnet in a slurry slamming into the glass electrode and breaking it.

I am about to requisition the Beckman pHI 10 so if anyone has any
thoughts on why this may not be my wisest move, please let me know ASAP.

                   Conservation DistList Instance 1:1
                   Distributed: Tuesday, May 17, 1988
                        Message Id: cdl-1-1-003
Received on Wednesday, 4 November, 1987

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