Hi Andy,

Since temperature is a critical item, you should monitor with a certified
thermometer.  The thermometer must be calibrated by an ISO 17025 accredited
calibration laboratory and have sufficient resolution over the intended
temperature range to be measured.

For example:

Hope this helps,

Ed Paski

On Tue, Jul 20, 2010 at 11:33 PM, Wolfram Meier-Augenstein <
[log in to unmask]> wrote:

> Hi Andy,
> We run our off-line acid digests in a solid metal heater block (VWR)
> with 72 positions.
> We "calibrated" the temperature control dial by measuring the
> temperature in a mock-up digest vial with an old fashioned thermometer
> (and later with a thermocouple). The vial was placed in the centre
> position of the block and every other position was occupied to create
> real life conditions.
> For the vial to reach 50 C we had to set the dial to 54.5 C.  However,
> this we did only (a) because we wanted to know what the offset was under
> typical conditions of use and (b) for reasons of writing an SOP and
> related record keeping. As other correspondents have already pointed
> out, as long as the principal of identical treatment is observed (i.e.
> standards are run concurrently and used for scale correction) absolute
> temperature is a secondary consideration.
> Temperature and reaction time become an issue when you are dealing with
> awkward customers such as ankerite, which even after a couple of days
> does not react with phosphoric acid at 25 C.
> Best,
> Wolfram
> ****************************
> Dr W Meier-Augenstein, CChem, FRSC
> Extension: 2624
> E-mail: [log in to unmask]
> URL (MRS):
> -----Original Message-----
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
> Behalf Of A. Schauer
> Sent: 21 July 2010 05:35
> To: [log in to unmask]
> Subject: [ISOGEOCHEM] 25*C
> Hi all,
> 1) How do you obtain a controlled 25*C for phosphoric acid digestion of
> carbonate in your lab? My lab varies around 22*C. It seems as though
> most water baths with heating option only control from 5*C above ambient
> to 99*C. Do you use a chiller model then or are you lucky enough to have
> a lab that is 20*C? Please either outline your method if home-built or
> provide a part number and manufacturer for your bath.
> 2) How do I know that my 25*C will be the same as your 25*C?
> Thank you.
> andy
> Andrew Schauer
> Earth and Space Sciences
> University of Washington
> Seattle, WA 98195
> 206.543.6327
> [log in to unmask]
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Edgar F. Paski, Ph.D.
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