Mercury triple point: isotopic composition and hydrostatic head correction

1Institut National de Métrologie (LNE-INM/CNAM) Workshop 732 – November 23-24, 2006

Mercury triple point: isotopic composition and hydrostatic head correction

(some ways for thought)



hl: distance between the middle of the sensing element and the free level of the substance when liquidhs: distance between the middle of the sensing element and the free level of the substance when solid

TP: triple pointMP: melting point(*) near the phase transition

hl

solid density

(*)liquid

density (*) hs

temperature variation with

depth correction

temperature variation due

to the apparent

depth variation

cm g/cm3 g/cm3 cm dT/dh (mK/cm) mK mK

Ar TP 10 1,624 1,416 8,72 0,033 0,330 0,042Hg TP 20 14,19 13,69 19,30 0,071 1,420 0,050Ga MP 20 5,93 6,09 19,47 -0,012 -0,240 -0,006



Source : IUPAC:International Union of Pure and Applied Chemistry

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Institut National de Métrologie (LNE-INM/CNAM) Workshop 732 – November 23-24, 2006


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Questions:

-What confidence in the isotopic composition determination ?

-What is the signification of the data spread in “IUPAC table” ?

Representative Isotopic Composition.

The values represent the isotopic composition of the chemicals and/or materials most commonly encountered in the laboratory.They may not, therefore, correspond to the most abundant natural material.

The uncertainties listed in parenthesis cover the range of probable variations of the materials as well as experimental errors.

(ISOTOPIC COMPOSITIONS OF THE ELEMENTS IUPAC 1997)

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Questions:

- For the thermometry … what are the sensitivity and distribution coefficients ? Are the uncertainties in the isotopic determinations sufficiently low ?

- Modelisation and/or experimental determinations of the influence of the isotopic composition on the triple point temperature?

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Atomic Isotope Natural Attained

Content of number

abundance enrichment in other isotopes

element at.%

the isotope in the product,

at.%

mercury Mercury-196 0.146 90

Mercury-198 10.02 99.6

Mercury-199 16.84 94

Mercury-200 23.13 96

Mercury-201 13.22 93

Mercury-202 29.86 99.8

Mercury-204 6.85 98

(Kurchatov Institute (Russian Research Center), Moscow)

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2 main obstacles !!!

The prices:

“Please take into account mercury isotopes are rather expensive

(for example Hg-196 with isotopic enrichment ~ 50,0% costs about 400.00US$/mg”

The chemical purity:

“Standard chemical purity is > 99,9% “

Modelisation ???

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Correlations in isotopic ratios can help ?

Mercury triple point: isotopic composition and hydrostatic head correction

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