The construction of a bakable changeover valve for high precision mass spectrometric comparison of the isotopic composition of gases is described. The leakage across the valve seats is about an order of magnitude smaller than the values published for similar valves in use, and the ``mixing correction'' which can be a significant correction to the experimental data is negligible.

1.
A. O.
Nier
,
Rev. Sci. Instrum.
18
,
398
(
1947
).
2.
C. R.
McKinney
,
J. M.
McCrea
,
S.
Epstein
,
H. A.
Allen
, and
H. C.
Urey
,
Rev. Sci. Instrum.
21
,
724
(
1950
).
3.
H.
Craig
,
Geochim. Cosmochim. Acta
12
,
133
(
1957
).
4.
H.
Craig
,
Proc. Spoleto Conf. on Stable Isotopes in Oceanographic Studies and Palaeotemperatures
3
,
161
(
1965
).
5.
G. D. Garlick, Ph.D. thesis (California Institute of Technology, 1964).
6.
P.
Deines
,
Int. J. Mass Spectrom. Ion Phys.
4
,
283
(
1970
).
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