Hi Wolfram, Robert and others,
I just realized it may look like a contradiction in my two messages on the
carbonates how a talk about T. In the first one I mentioned T is highly
important, and in the second at some stage I claim T is not important. Sound
strange, but I meant two different things with these. So, to prevent
confusion, let me tell what I mean with the T being important or not.
T is important only for the isotopic fractionation factor and should be
controlled during the acid digestion carefully (± 1 degree C or better).
It is fully unimportant at what T we digest, as long as we know the isotopic
fractionation factor at that specific T. This was what I meant, and nothing
I sent this before others will point to this fact... Better to clarify!
> From: Wolfram Meier-Augenstein <[log in to unmask]>
> Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
> Date: Sun, 25 Jul 2010 09:53:20 +0100
> To: <[log in to unmask]>
> Subject: Re: [ISOGEOCHEM] 25*C and SI in concrete
> Hi Pier,
> So, what do you propose people should do who happen to work with carbonates
> that are resilient to acid digest at 25 C but require higher temperatures to
> react, or, even "better", who are working with mixed carbonates where one
> (mineral) fraction reacts at 25 C but the other only just, and where 18O
> fractionation slopes will differ?
> I call this the normative forces and facts of life; it's no good to moan this
> should be done strictly observing condition X because of Y if the reaction
> doesn't work at condition X in the first place. One has to be pragmatic and do
> they best one can under the circumstances.
> As Willi pointed out already, to report 18O data to the standard temperature
> of 25 C independent of the actual temperature the digest had to be performed,
> 18O values must be back-calculated to 25 C.
> What this boils down to is observance of the principle-of-identical treatment,
> i.e. concurrent digest and analysis of NBS19 and LSVEC plus one or two other
> standards as quality control (for the correction).
> From: Stable Isotope Geochemistry on behalf of Pier de Groot
> Sent: Sat 24/07/2010 17:23
> To: [log in to unmask]
> Subject: Re: [ISOGEOCHEM] 25*C and SI in concrete
> Hi Robert and others,
> First my two cents for references on concrete/mortar and isotopes:
> Zouridakis, N. M., I. G. Economou, et al. (2000). "Investigation of the
> physicochemical characteristics of ancient mortars by static and dynamic
> studies." Cement Concrete Res. 30(7): 1151-1155 doi:
> Rafai, N., R. Letolle, et al. (1992). "Carbonation-decarbonation of
> concretes studied by the way of carbon and oxygen stable isotopes." Cement
> Concrete Res. 22(5): 882-890 doi: 10.1016/0008-8846(92)90112-9.
> Létolle, R., P. Gégout, et al. (1992). "Stable isotopes of carbon and oxygen
> for the study of carbonation/decarbonation processes in concretes." Cement
> Concrete Res. 22(2-3): 235-240 doi: 10.1016/0008-8846(92)90061-Y.
> Häussler, F., F. Eichhorn, et al. (1990). "Monitoring of the hydration
> process of hardening cement pastes by small-angle neutron scattering."
> Cement Concrete Res. 20(4): 644-654 doi: 10.1016/0008-8846(90)90107-9.
> And maybe still of use:
> Graham, I. J., R. L. Goguel, et al. (2000). "Use of strontium isotopes to
> determine the origin of cement in concretes: Case examples from New
> Zealand." Cement Concrete Res. 30(7): 1105-1111 doi:
> Than about the carbonate-isotope analytical procedure:
> Your statement that temperature can be ignored in acid digestion of
> carbonates for isotopic determinations did alarm me quite a lot, at least if
> considering oxygen isotope determinations...
> The oxygen isotopic fractionation of phosphoric acid digestion of the
> carbonates is temperature dependent* in a non-linear way to my knowledge. If
> this fractionation is not linear temperature is highly important, since if
> we calibrate our system at 25°C or 22°C (or other T's) by acid digestion
> different fractionation factors have to be used to estimate the value to
> correct/calibrate to the proper scale.
> Maybe you meant this yourself, but if so, I did not get the right picture
> the way you described things - certainly not by the statmeent on
> temperatures in your posting to the list.
> * Let me quote from Rosenbaum and Sheppard (GCA, 1986, 50: 1147-1150):
> "Since reaction with phosphoric acid liberates only two thirds of the oxygen
> of the carbonate as CO2 gas, a temperature dependent fractionation of oxygen
> isotopes occur."
> Best regards,
> Delta Isotopes Consultancy
> Dr. Pier A. de Groot
> De Schans 47
> 3945 Ham (Oostham)
> Tel. +32 (0)11 72 77 66
> e-mail: [log in to unmask]
> Chair of the Programme Group ³Isotopes in Geosciences² [IG] and Secretary
> for IG in the ³Geochemistry, Mineralogy, Petrology, Volcanology² [GMPV]
> division of the European Geoscience Union (EGU)
> EGU Home web-site: http://www.egu.eu/
> Scientific Committee member of BASIS (Benelux Association of Stable Isotope
> Visit the Elsevier WEB-site about my ³Handbook of Stable Isotope Analytical
> Techniques² Vol-II (published Nov. 17, 2008):
> and Vol-I (was published Dec. 27, 2004) at:
>> From: Robert van Geldern <[log in to unmask]>
>> Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
>> Date: Wed, 21 Jul 2010 09:11:14 +0200
>> To: <[log in to unmask]>
>> Subject: Re: [ISOGEOCHEM] 25*C
>> Am 21.07.2010 um 06:34 schrieb A. Schauer:
>>> 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
>>> 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?
>> to (2) As long as you run calibrated standards (CO-1, NBS 19 or calibrated
>> standards) together with your at identical conditions and normalize your data
>> to the defined value (e.g. d13C for NBS 19 = +1,95 permil) absolute
>> temperature does not matter at all. The standards in our lab will be same as
>> in your lab, so temperature can be ignored. You can run your carbonates at
>> temperature you want as long as your temperature is _constant_ (in case of
>> 18O analysis) for your standards and your samples.
>> to (1) since we run a gasbench with temperature stabilzed tray we never built
>> our own system. But 18O water analysis (also temperature sensitive) I was
>> happy by using a standard drying oven. We placed a styrofoam box with a tube
>> rack in the drying cabinet and set the temperature controller to 26°C.
>> However, since the acid reaction is a one way lane (instead of water
>> equilibration) you have to be fast by injecting you acid. Otherwise your
>> will cool down after taking it out of the oven... :-)
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