CRC press handbook of chemistry and physics

PREFACE

This is the first edition of the CRC Handbook of Chemistry and Physics for the
21st Century (as “century” is officially defined). Few would dispute that the 20th Century
was the century of science; major paradigm shifts took place first in physics and
chemistry and, in the second half of the century, in biology. The “Rubber Handbook”, so-
called after the original name of its publisher, the Chemical Rubber Company, was a
fixture for almost all of that eventful century. When the first edition appeared in 1913, the
electron had been known for only 17 years, there were 81 elements, and the Bohr theory
of the hydrogen atom was still in press. The Handbook was a significant innovation.
While systematic compilation of data from the chemistry and physics literature had
begun earlier, especially in Germany, the massive tomes that were published by
Beilstein, Gmelin, and Landolt-Börnstein were strictly for libraries. The Rubber
Handbook appears to have been the first compact, low-price volume of reference data
suitable for students and individual researchers to keep on their desk or laboratory bench.
It quickly became a standard and grew from its original 116 pages to the present size of
over 2500 pages.

Generations of students have relied on the CRC Handbook as a resource in their
studies, but the impact has been much broader. Senior research scientists, engineers, and
workers in other fields have used the book extensively. Linus Pauling, perhaps the most
influential chemist of the 20th century, made the following comments a few years before
his death:

“People who have interviewed me have commented on the extensive knowledge that I
have about the properties of substances, especially inorganic compounds, including
minerals. I attribute this knowledge in part to the fact that I possessed the Rubber
Handbook. I remember clearly the five summers, beginning in 1919, when I worked as a
paving-plant inspector, supervising the laying of bituminous pavement in the
mountainous region of southern Oregon. For much of the time I was free to read, just
keeping an eye on the operation of the paving plant. I remember the book that I read over

and over was the Rubber Handbook. I puzzled over the tables of properties - hardness,
color, melting and boiling point, density, magnetic properties, and others - trying to think
of reasonable explanations of the empirical data. Only in the 1920s and 1930s did I have
some success in this effort.”

Pauling’s “success” was the first step in our ability to relate the physical and chemical
behavior of bulk materials to their molecular structure in a quantitative manner.

One factor in the success of the Handbook has been its annual revisions. This
practice, followed throughout the century except for a few wartime years, permitted the
replacement of old data with new and more accurate values, as well as the introduction of
new topics that became important as science moved forward. This policy has helped the
Handbook meet the needs of the scientific community in a timely fashion.

The 82nd Edition continues the tradition of updates and improvements. The major
change is a revised and expanded table of Physical Constants of Inorganic Compounds.
The number of compounds has been increased by 12%, the format improved, and the
constants updated. In addition, quantitative data on solubility in water are now included
in the table, and a formula index has been added. Other tables that have been expanded
and updated include:
• Critical Constants
• Aqueous Solubility and Henry’s Law Constants of Organic Compounds
• Chemical Carcinogens
• Threshold Limits for Airborne Contaminants
• Nomenclature for Organic Polymers
• Standard Atomic Weights
• Atomic Masses and Abundances
• Table of the Isotopes
New topics covered in this edition include:
• Surface Tension of Aqueous Mixtures

• Viscosity of Carbon Dioxide along the Saturation Line
• Gibbs Energy of Formation for Important Biological Species
• Optical Properties of Inorganic and Organic Solids
• Interstellar Molecules
• Allocation of Frequencies in the Radio Spectrum
• Units for Magnetic Properties

This electronic version of the Handbook of Chemistry and Physics contains all the
material from the print version of the 82nd Edition, as well as some additional data that
could not be accommodated in the printed book. Powerful search capabilities, which are
explained in the Help messages, greatly facilitate the task of locating the data.

The Editor will appreciate suggestions on new topics for the Handbook and
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Comments may also be sent by electronic mail to

The Handbook of Chemistry and Physics is dependent on the efforts of many
contributors throughout the world. I appreciate the valuable suggestions that have come
from the Editorial Advisory Board and from many users. I should also like to thank
Susan Fox and the rest of the production team at CRC Press for their excellent support.

David R. Lide
January 1, 2001

This Edition is Dedicated to the Memory of David Reynolds Lide (1901-1976) and
Kate Simmons Lide (1896-1991)

This work contains information obtained from authentic and highly regarded
sources. Reprinted material is quoted with permission, and sources are indicated. A

wide variety of references are listed. Reasonable efforts have been made to publish
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responsibility for the validity of all materials or for the consequences of their use.

© Copyright CRC Press LLC 2002

FUNDAMENTAL PHYSICAL CONSTANTS
Peter J. Mohr and Barry N. Taylor
These tables give the 1998 self-consistent set of values of the basic constants and conversion factors of
physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for
international use. The 1998 set replaces the previous set of constants recommended by CODATA in 1986; assigned
uncertainties have been reduced by a factor of 1/5 to 1/12 (and sometimes even greater) relative to the 1986
uncertainties. The recommended set is based on a least-squares adjustment involving all of the relevant experimental
and theoretical data available through December 31, 1998. Full details of the input data and the adjustment
procedure are given in Reference 1.
The 1998 adjustment was carried out by P. J. Mohr and B. N. Taylor of the National Institute of Standards
and Technology (NIST) under the auspices of the CODATA Task Group on Fundamental Constants. The Task
Group was established in 1969 with the aim of periodically providing the scientific and technological communities
with a self-consistent set of internationally recommended values of the fundamental physical constants based on all
applicable information available at a given point in time. The first set was published in 1973 and was followed by a
revised set first published in 1986; the current 1998 set first appeared in 1999. In the future, the CODATA Task
Group plans to take advantage of the high level of automation developed for the current set in order to issue a new
set of recommended values at least every four years.
At the time of completion of the 1998 adjustment, the membership of the Task Group was as follows:
F. Cabiati, Istituto Elettrotecnico Nazionale “Galileo Ferraris,” Italy
E. R. Cohen, Science Center, Rockwell International (retired), United States of America
T. Endo, Electrotechnical Laboratory, Japan
R. Liu, National Institute of Metrology, China (People’s Republic of)
B. A. Mamyrin, A. F. Ioffe Physical-Technical Institute, Russian Federation
P. J. Mohr, National Institute of Standards and Technology, United States of America

F. Nez, Laboratoire Kastler-Brossel, France
B. W. Petley, National Physical Laboratory, United Kingdom
T. J. Quinn, Bureau International des Poids et Mesures
B. N. Taylor, National Institute of Standards and Technology, United States of America
V. S. Tuninsky, D. I. Mendeleyev All-Russian Research Institute for Metrology, Russian Federation
W. Wöger, Physikalisch-Technische Bundesanstalt, Germany
B. M. Wood, National Research Council, Canada
REFERENCES
1. Mohr, Peter J., and Taylor, Barry N., J. Phys Chem. Ref. Data 28, 1713, 1999; Rev. Mod. Phys. 72, 351,
2000. The 1998 set of recommended values is also available at the Web site of the Fundamental Constants Data
Center of the NIST Physics Laboratory: />

Fundamental Physical Constants
Relative std.
Quantity Symbol Value Unit uncert. u
r
UNIVERSAL
speed of light in vacuum c, c
0
299 792458 m s
−1
(exact)
magnetic constant µ
0
4π ×10
−7
NA
−2
= 12.566 370614 ×10
−7
NA
−2
(exact)
electric constant 1/µ
0
c
2

ε
0
8.854187 817 × 10
−12
Fm
−1
(exact)
characteristic impedance
of vacuum
√
µ
0
/
0
= µ
0
cZ
0
376.730313 461  (exact)
Newtonian constant
of gravitation G 6.673(10) ×10
−11
m
3
kg
−1
s
−2
1.5 ×10
−3

G/c 6.707(10) ×10
−39
(GeV/c
2
)
−2
1.5 ×10
−3
Planck constant h 6.626 068 76(52) × 10
−34
Js 7.8 ×10
−8
in eV s 4.135 667 27(16) × 10
−15
eV s 3.9 ×10
−8
h/2π  1.054571 596(82) × 10
−34
Js 7.8 ×10
−8
in eV s 6.582118 89(26) × 10
−16
eV s 3.9 ×10
−8
Planck mass (c/G)
1/2
m
P
2.1767(16) × 10
−8

kg 7.5 ×10
−4
Planck length /m
P
c = (G/c
3
)
1/2
l
P
1.6160(12) × 10
−35
m7.5 ×10
−4
Planck time l
P
/c = (G/c
5
)
1/2
t
P
5.3906(40) × 10
−44
s7.5 ×10
−4
ELECTROMAGNETIC
elementary charge e 1.602176 462(63) × 10
−19
C3.9 ×10

−8
e/h 2.417 989 491(95) × 10
14
AJ
−1
3.9 ×10
−8
magnetic flux quantum h/2e 
0
2.067 833 636(81) × 10
−15
Wb 3.9 × 10
−8
conductance quantum 2e
2
/hG
0
7.748 091 696(28) × 10
−5
S3.7 ×10
−9
inverse of conductance quantum G
−1
0
12906.403 786(47) 3.7 ×10
−9
Josephson constant
a
2e/hK
J

483 597.898(19) × 10
9
Hz V
−1
3.9 ×10
−8
von Klitzing constant
b
h/e
2
= µ
0
c/2α R
K
25 812.807 572(95) 3.7 ×10
−9
Bohr magneton e/2m
e
µ
B
927.400899(37) ×10
−26
JT
−1
4.0 × 10
−8
in eV T
−1
5.788 381 749(43) × 10
−5

eV T
−1
7.3 ×10
−9
µ
B
/h 13.996 246 24(56) × 10
9
Hz T
−1
4.0 × 10
−8
µ
B
/hc 46.686 4521(19) m
−1
T
−1
4.0 × 10
−8
µ
B
/k 0.671 7131(12) KT
−1
1.7 ×10
−6
nuclear magneton e/2m
p
µ
N

5.050783 17(20) × 10
−27
JT
−1
4.0 × 10
−8
in eV T
−1
3.152451 238(24) × 10
−8
eV T
−1
7.6 ×10
−9
µ
N
/h 7.622593 96(31) MHz T
−1
4.0 × 10
−8
µ
N
/hc 2.542623 66(10) ×10
−2
m
−1
T
−1
4.0 × 10
−8

µ
N
/k 3.658 2638(64) × 10
−4
KT
−1
1.7 ×10
−6
ATOMIC AND NUCLEAR
General
fine-structure constant e
2
/4π
0
c α 7.297 352533(27) ×10
−3
3.7 ×10
−9
inverse fine-structure constant α
−1
137.035 999 76(50) 3.7 ×10
−9

Fundamental Physical Constants
Relative std.
Quantity Symbol Value Unit uncert. u
r
Rydberg constant α
2
m
e
c/2hR
∞
10 973 731.568 549(83) m
−1
7.6 ×10

−12
R
∞
c 3.289 841 960368(25) × 10
15
Hz 7.6 ×10
−12
R
∞
hc 2.179871 90(17) × 10
−18
J7.8 ×10
−8
R
∞
hc in eV 13.605 691 72(53) eV 3.9 ×10
−8
Bohr radius α/4π R
∞
= 4π
0

2
/m
e
e
2
a
0
0.529 177 2083(19) × 10

−10
m3.7 ×10
−9
Hartree energy e
2
/4πε
0
a
0
= 2R
∞
hc
= α
2
m
e
c
2
E
h
4.359 743 81(34) × 10
−18
J7.8 ×10
−8
in eV 27.211 3834(11) eV 3.9 ×10
−8
quantum of circulation h/2m
e
3.636 947 516(27) × 10
−4

m
2
s
−1
7.3 ×10
−9
h/m
e
7.273 895 032(53) × 10
−4
m
2
s
−1
7.3 ×10
−9
Electroweak
Fermi coupling constant
c
G
F
/(c)
3
1.166 39(1) × 10
−5
GeV
−2
8.6 ×10
−6
weak mixing angle

d
θ
W
(on-shell scheme)
sin
2
θ
W
= s
2
W
≡ 1 −(m
W
/m
Z
)
2
sin
2
θ
W
0.2224(19) 8.7 ×10
−3
Electron, e
−
electron mass m
e
9.109 381 88(72) × 10
−31
kg 7.9 ×10

−8
in u, m
e
= A
r
(e) u (electron
relative atomic mass times u) 5.485 799 110(12) × 10
−4
u2.1 ×10
−9
energy equivalent m
e
c
2
8.187 10414(64) ×10
−14
J7.9 ×10
−8
in MeV 0.510 998 902(21) MeV 4.0 ×10
−8
electron-muon mass ratio m
e
/m
µ
4.836 33210(15) ×10
−3
3.0 ×10
−8
electron-tau mass ratio m
e

/m
τ
2.875 55(47) × 10
−4
1.6 ×10
−4
electron-proton mass ratio m
e
/m
p
5.446 170232(12) ×10
−4
2.1 ×10
−9
electron-neutron mass ratio m
e
/m
n
5.438 673 462(12) × 10
−4
2.2 ×10
−9
electron-deuteron mass ratio m
e
/m
d
2.724437 1170(58) × 10
−4
2.1 ×10
−9

electron to alpha particle mass ratio m
e
/m
α
1.370933 5611(29) × 10
−4
2.1 ×10
−9
electron charge to mass quotient −e/m
e
−1.758 820174(71) ×10
11
Ckg
−1
4.0 ×10
−8
electron molar mass N
A
m
e
M(e), M
e
5.485 799 110(12) × 10
−7
kg mol
−1
2.1 ×10
−9
Compton wavelength h/m
e

c λ
C
2.426 310215(18) ×10
−12
m7.3 ×10
−9
λ
C
/2π = αa
0
= α
2
/4π R
∞

C
386.159 2642(28) × 10
−15
m7.3 ×10
−9
classical electron radius α
2
a
0
r
e
2.817 940285(31) ×10
−15
m1.1 ×10
−8

Thomson cross section (8π/3)r
2
e
σ
e
0.665 245 854(15) × 10
−28
m
2
2.2 ×10
−8
electron magnetic moment µ
e
−928.476 362(37) × 10
−26
JT
−1
4.0 ×10
−8
to Bohr magneton ratio µ
e
/µ
B
−1.001 159 6521869(41) 4.1 ×10
−12
to nuclear magneton ratio µ
e
/µ
N
−1 838.281 9660(39) 2.1 ×10

−9
electron magnetic moment
anomaly |µ
e
|/µ
B
− 1 a
e
1.159 6521869(41) ×10
−3
3.5 ×10
−9
electron g-factor −2(1 +a
e
) g
e
−2.002319 3043737(82) 4.1 × 10
−12
electron-muon
magnetic moment ratio µ
e
/µ
µ
206.766 9720(63) 3.0 ×10
−8

Fundamental Physical Constants
Relative std.
Quantity Symbol Value Unit uncert. u
r
electron-proton
magnetic moment ratio µ
e
/µ
p
−658.2106875(66) 1.0 ×10

−8
electron to shielded proton
magnetic moment ratio µ
e
/µ

p
−658.227 5954(71) 1.1 × 10
−8
(H
2
O, sphere, 25
◦
C)
electron-neutron
magnetic moment ratio µ
e
/µ
n
960.92050(23) 2.4 × 10
−7
electron-deuteron
magnetic moment ratio µ
e
/µ
d
−2143.923 498(23) 1.1 × 10
−8
electron to shielded helion
e

magnetic moment ratio µ
e
/µ

h
864.058 255(10) 1.2 × 10
−8
(gas, sphere, 25
◦
C)
electron gyromagnetic ratio 2|µ
e
|/ γ
e
1.760859 794(71) × 10
11
s
−1
T
−1
4.0 × 10
−8
γ
e
/2π 28024.9540(11) MHz T
−1
4.0 × 10
−8
Muon, µ
−

muon mass m
µ
1.883 531 09(16) × 10
−28
kg 8.4 ×10
−8
in u, m
µ
= A
r
(µ) u (muon
relative atomic mass times u) 0.113428 9168(34) u3.0 × 10
−8
energy equivalent m
µ
c
2
1.692833 32(14) ×10
−11
J8.4 × 10
−8
in MeV 105.658 3568(52) MeV 4.9 × 10
−8
muon-electron mass ratio m
µ
/m
e
206.768 2657(63) 3.0 × 10
−8
muon-tau mass ratio m

µ
/m
τ
5.945 72(97) × 10
−2
1.6 × 10
−4
muon-proton mass ratio m
µ
/m
p
0.112609 5173(34) 3.0 × 10
−8
muon-neutron mass ratio m
µ
/m
n
0.112454 5079(34) 3.0 × 10
−8
muon molar mass N
A
m
µ
M(µ), M
µ
0.113 428 9168(34) × 10
−3
kg mol
−1
3.0 × 10

−8
muon Compton wavelength h/m
µ
c λ
C,µ
11.734441 97(35) × 10
−15
m2.9 × 10
−8
λ
C,µ
/2π 
C,µ
1.867 594444(55) ×10
−15
m2.9 × 10
−8
muon magnetic moment µ
µ
−4.490448 13(22) ×10
−26
JT
−1
4.9 × 10
−8
to Bohr magneton ratio µ
µ
/µ
B
−4.841 97085(15) ×10

−3
3.0 × 10
−8
to nuclear magneton ratio µ
µ
/µ
N
−8.890597 70(27) 3.0 × 10
−8
muon magnetic moment anomaly
|µ
µ
|/(e/2m
µ
) − 1 a
µ
1.165 916 02(64) × 10
−3
5.5 × 10
−7
muon g-factor −2(1 +a
µ
) g
µ
−2.002331 8320(13) 6.4 × 10
−10
muon-proton
magnetic moment ratio µ
µ
/µ

p
−3.183 345 39(10) 3.2 × 10
−8
Tau, τ
−
tau mass
f
m
τ
3.167 88(52) × 10
−27
kg 1.6 ×10
−4
in u, m
τ
= A
r
(τ) u(tau
relative atomic mass times u) 1.90774(31) u1.6 × 10
−4
energy equivalent m
τ
c
2
2.847 15(46) × 10
−10
J1.6 × 10
−4
in MeV 1 777.05(29) MeV 1.6 ×10
−4

Fundamental Physical Constants
Relative std.
Quantity Symbol Value Unit uncert. u
r
tau-electron mass ratio m

τ
/m
e
3 477.60(57) 1.6 × 10
−4
tau-muon mass ratio m
τ
/m
µ
16.8188(27) 1.6 × 10
−4
tau-proton mass ratio m
τ
/m
p
1.893 96(31) 1.6 ×10
−4
tau-neutron mass ratio m
τ
/m
n
1.891 35(31) 1.6 ×10
−4
tau molar mass N
A
m
τ
M(τ), M
τ
1.907 74(31) × 10

−3
kg mol
−1
1.6 × 10
−4
tau Compton wavelength h/m
τ
c λ
C,τ
0.697 70(11) × 10
−15
m1.6 ×10
−4
λ
C,τ
/2π 
C,τ
0.111 042(18) × 10
−15
m1.6 ×10
−4
Proton, p
proton mass m
p
1.672621 58(13) ×10
−27
kg 7.9 ×10
−8
in u, m
p

= A
r
(p) u (proton
relative atomic mass times u) 1.007 276 466 88(13) u1.3 ×10
−10
energy equivalent m
p
c
2
1.503 277 31(12) × 10
−10
J7.9 ×10
−8
in MeV 938.271 998(38) MeV 4.0 ×10
−8
proton-electron mass ratio m
p
/m
e
1 836.1526675(39) 2.1 × 10
−9
proton-muon mass ratio m
p
/m
µ
8.88024408(27) 3.0 × 10
−8
proton-tau mass ratio m
p
/m

τ
0.527 994(86) 1.6 ×10
−4
proton-neutron mass ratio m
p
/m
n
0.998 623 478 55(58) 5.8 ×10
−10
proton charge to mass quotient e/m
p
9.578 83408(38) ×10
7
Ckg
−1
4.0 × 10
−8
proton molar mass N
A
m
p
M(p), M
p
1.007 276 466 88(13) × 10
−3
kg mol
−1
1.3 × 10
−10
proton Compton wavelength h/m

p
c λ
C,p
1.321 409 847(10) ×10
−15
m7.6 ×10
−9
λ
C,p
/2π 
C,p
0.210308 9089(16) ×10
−15
m7.6 ×10
−9
proton magnetic moment µ
p
1.410606 633(58) ×10
−26
JT
−1
4.1 × 10
−8
to Bohr magneton ratio µ
p
/µ
B
1.521 032203(15) ×10
−3
1.0 × 10

−8
to nuclear magneton ratio µ
p
/µ
N
2.792847 337(29) 1.0 ×10
−8
proton g-factor 2µ
p
/µ
N
g
p
5.585 694675(57) 1.0 ×10
−8
proton-neutron
magnetic moment ratio µ
p
/µ
n
−1.459 898 05(34) 2.4 × 10
−7
shielded proton magnetic moment µ

p
1.410570399(59) ×10
−26
JT
−1
4.2 × 10

−8
(H
2
O, sphere, 25
◦
C)
to Bohr magneton ratio µ

p
/µ
B
1.520993 132(16) × 10
−3
1.1 × 10
−8
to nuclear magneton ratio µ

p
/µ
N
2.792775 597(31) 1.1 ×10
−8
proton magnetic shielding
correction 1 − µ

p
/µ
p
σ


p
25.687(15) × 10
−6
5.7 × 10
−4
(H
2
O, sphere, 25
◦
C)
proton gyromagnetic ratio 2µ
p
/ γ
p
2.675 22212(11) ×10
8
s
−1
T
−1
4.1 × 10
−8
γ
p
/2π 42.577 4825(18) MHz T
−1
4.1 × 10
−8
shielded proton gyromagnetic
ratio 2µ


p
/ γ

p
2.675 153 41(11) × 10
8
s
−1
T
−1
4.2 × 10
−8
(H
2
O, sphere, 25
◦
C)
γ

p
/2π 42.576 3888(18) MHz T
−1
4.2 × 10
−8
Neutron, n

Fundamental Physical Constants
Relative std.
Quantity Symbol Value Unit uncert. u
r
neutron mass m
n
1.674927 16(13) × 10
−27
kg 7.9 ×10

−8
in u, m
n
= A
r
(n) u (neutron
relative atomic mass times u) 1.008 664915 78(55) u5.4 × 10
−10
energy equivalent m
n
c
2
1.505 349 46(12) × 10
−10
J7.9 ×10
−8
in MeV 939.565 330(38) MeV 4.0 ×10
−8
neutron-electron mass ratio m
n
/m
e
1 838.683 6550(40) 2.2 ×10
−9
neutron-muon mass ratio m
n
/m
µ
8.892484 78(27) 3.0 ×10
−8

neutron-tau mass ratio m
n
/m
τ
0.528 722(86) 1.6 ×10
−4
neutron-proton mass ratio m
n
/m
p
1.001 378 418 87(58) 5.8 ×10
−10
neutron molar mass N
A
m
n
M(n), M
n
1.008 664915 78(55) × 10
−3
kg mol
−1
5.4 ×10
−10
neutron Compton wavelength h/m
n
c λ
C,n
1.319 590898(10) ×10
−15

m7.6 ×10
−9
λ
C,n
/2π 
C,n
0.210019 4142(16) × 10
−15
m7.6 ×10
−9
neutron magnetic moment µ
n
−0.966 236 40(23) × 10
−26
JT
−1
2.4 ×10
−7
to Bohr magneton ratio µ
n
/µ
B
−1.041 875 63(25) × 10
−3
2.4 ×10
−7
to nuclear magneton ratio µ
n
/µ
N

−1.913 04272(45) 2.4 ×10
−7
neutron g-factor 2µ
n
/µ
N
g
n
−3.826 085 45(90) 2.4 ×10
−7
neutron-electron
magnetic moment ratio µ
n
/µ
e
1.040668 82(25) × 10
−3
2.4 ×10
−7
neutron-proton
magnetic moment ratio µ
n
/µ
p
−0.684979 34(16) 2.4 ×10
−7
neutron to shielded proton
magnetic moment ratio µ
n
/µ


p
−0.684996 94(16) 2.4 ×10
−7
(H
2
O, sphere, 25
◦
C)
neutron gyromagnetic ratio 2|µ
n
|/ γ
n
1.832471 88(44) × 10
8
s
−1
T
−1
2.4 ×10
−7
γ
n
/2π 29.1646958(70) MHz T
−1
2.4 ×10
−7
Deuteron, d
deuteron mass m
d

3.343 583 09(26) × 10
−27
kg 7.9 ×10
−8
in u, m
d
= A
r
(d) u (deuteron
relative atomic mass times u) 2.013 553 21271(35) u1.7 ×10
−10
energy equivalent m
d
c
2
3.005 06262(24) ×10
−10
J7.9 ×10
−8
in MeV 1 875.612762(75) MeV 4.0 ×10
−8
deuteron-electron mass ratio m
d
/m
e
3 670.4829550(78) 2.1 ×10
−9
deuteron-proton mass ratio m
d
/m

p
1.999 007 50083(41) 2.0 × 10
−10
deuteron molar mass N
A
m
d
M(d), M
d
2.013 553 21271(35) ×10
−3
kg mol
−1
1.7 ×10
−10
deuteron magnetic moment µ
d
0.433 073 457(18) × 10
−26
JT
−1
4.2 ×10
−8
to Bohr magneton ratio µ
d
/µ
B
0.466 975 4556(50) × 10
−3
1.1 ×10

−8
to nuclear magneton ratio µ
d
/µ
N
0.857 438 2284(94) 1.1 ×10
−8
deuteron-electron
magnetic moment ratio µ
d
/µ
e
−4.664345 537(50) × 10
−4
1.1 ×10
−8
deuteron-proton
magnetic moment ratio µ
d
/µ
p
0.307 0122083(45) 1.5 ×10
−8

Fundamental Physical Constants
Relative std.
Quantity Symbol Value Unit uncert. u
r
deuteron-neutron
magnetic moment ratio µ
d
/µ
n
−0.448 206 52(11) 2.4 ×10
−7
Helion, h

helion mass
e
m
h
5.006 411 74(39) × 10
−27
kg 7.9 ×10
−8
in u, m
h
= A
r
(h) u (helion
relative atomic mass times u) 3.014932 23469(86) u2.8 ×10
−10
energy equivalent m
h
c
2
4.499 538 48(35) × 10
−10
J7.9 ×10
−8
in MeV 2 808.391 32(11) MeV 4.0 ×10
−8
helion-electron mass ratio m
h
/m
e
5 495.885 238(12) 2.1 ×10

−9
helion-proton mass ratio m
h
/m
p
2.993 152658 50(93) 3.1 ×10
−10
helion molar mass N
A
m
h
M(h), M
h
3.014932 23469(86) ×10
−3
kg mol
−1
2.8 ×10
−10
shielded helion magnetic moment µ

h
−1.074552 967(45) × 10
−26
JT
−1
4.2 ×10
−8
(gas, sphere, 25
◦

C)
to Bohr magneton ratio µ

h
/µ
B
−1.158 671 474(14) × 10
−3
1.2 ×10
−8
to nuclear magneton ratio µ

h
/µ
N
−2.127 497 718(25) 1.2 ×10
−8
shielded helion to proton
magnetic moment ratio µ

h
/µ
p
−0.761 766 563(12) 1.5 ×10
−8
(gas, sphere, 25
◦
C)
shielded helion to shielded proton
magnetic moment ratio µ


h
/µ

p
−0.761 786 1313(33) 4.3 ×10
−9
(gas/H
2
O, spheres, 25
◦
C)
shielded helion gyromagnetic
ratio 2|µ

h
|/ γ

h
2.037 894764(85) ×10
8
s
−1
T
−1
4.2 ×10
−8
(gas, sphere, 25
◦
C)

γ

h
/2π 32.4341025(14) MHz T
−1
4.2 ×10
−8
Alpha particle, α
alpha particle mass m
α
6.644655 98(52) × 10
−27
kg 7.9 ×10
−8
in u, m
α
= A
r
(α) u (alpha particle
relative atomic mass times u) 4.001506 1747(10) u2.5 ×10
−10
energy equivalent m
α
c
2
5.971 918 97(47) × 10
−10
J7.9 ×10
−8
in MeV 3 727.379 04(15) MeV 4.0 ×10

−8
alpha particle to electron mass ratio m
α
/m
e
7 294.299 508(16) 2.1 ×10
−9
alpha particle to proton mass ratio m
α
/m
p
3.972599 6846(11) 2.8 ×10
−10
alpha particle molar mass N
A
m
α
M(α), M
α
4.001 506 1747(10) × 10
−3
kg mol
−1
2.5 ×10
−10
PHYSICO-CHEMICAL
Avogadro constant N
A
, L 6.022141 99(47) ×10
23

mol
−1
7.9 ×10
−8
atomic mass constant
m
u
=
1
12
m(
12
C) = 1u m
u
1.660538 73(13) × 10
−27
kg 7.9 ×10
−8
= 10
−3
kg mol
−1
/N
A
energy equivalent m
u
c
2
1.492417 78(12) × 10
−10

J7.9 ×10
−8
in MeV 931.494013(37) MeV 4.0 ×10
−8
Faraday constant
g
N
A
eF96 485.3415(39) Cmol
−1
4.0 ×10
−8

Fundamental Physical Constants
Relative std.
Quantity Symbol Value Unit uncert. u
r
molar Planck constant N
A
h 3.990312 689(30) ×10
−10
Jsmol
−1
7.6 ×10
−9
N
A
hc 0.119 626 56492(91) Jmmol
−1
7.6 ×10
−9
molar gas constant R 8.314472(15) Jmol
−1
K
−1
1.7 ×10

−6
Boltzmann constant R/N
A
k 1.3806503(24) × 10
−23
JK
−1
1.7 ×10
−6
in eV K
−1
8.617 342(15) × 10
−5
eV K
−1
1.7 ×10
−6
k/ h 2.083 6644(36) × 10
10
Hz K
−1
1.7 ×10
−6
k/ hc 69.50356(12) m
−1
K
−1
1.7 ×10
−6
molar volume of ideal gas RT/ p

T = 273.15 K, p = 101.325 kPa V
m
22.413 996(39) × 10
−3
m
3
mol
−1
1.7 ×10
−6
Loschmidt constant N
A
/V
m
n
0
2.686 7775(47) × 10
25
m
−3
1.7 ×10
−6
T = 273.15 K, p = 100 kPa V
m
22.710981(40) ×10
−3
m
3
mol
−1

1.7 ×10
−6
Sackur-Tetrode constant
(absolute entropy constant)
h
5
2
+ ln[(2πm
u
kT
1
/h
2
)
3/2
kT
1
/ p
0
]
T
1
= 1K, p
0
= 100 kPa S
0
/R −1.151 7048(44) 3.8 ×10
−6
T
1

= 1K, p
0
= 101. 325 kPa −1.1648678(44) 3.7 × 10
−6
Stefan-Boltzmann constant
(π
2
/60)k
4
/
3
c
2
σ 5.670400(40) ×10
−8
Wm
−2
K
−4
7.0 ×10
−6
first radiation constant 2πhc
2
c
1
3.741 771 07(29) × 10
−16
Wm
2
7.8 ×10

−8
first radiation constant for spectral radiance 2hc
2
c
1L
1.191 042722(93) × 10
−16
Wm
2
sr
−1
7.8 ×10
−8
second radiation constant hc/kc
2
1.438 7752(25) × 10
−2
mK 1.7 ×10
−6
Wien displacement law constant
b = λ
max
T = c
2
/4.965 114231 b 2.897 7686(51) × 10
−3
mK 1.7 ×10
−6
a
See the “Adopted values” table for the conventional value adopted internationally for realizing representations of the volt using the Joseph-

son effect.
b
See the “Adopted values” table for the conventional value adopted internationally for realizing representations of the ohm using the quantum Hall
effect.
c
Value recommended by the Particle Data Group, Caso et al., Eur. Phys. J. C 3(1-4), 1-794 (1998).
d
Based on the ratio of the masses of the W and Z bosons m
W
/m
Z
recommended by the Particle Data Group (Caso et al., 1998). The value for
sin
2
θ
W
they recommend, which is based on a particular variant of the modified minimal subtraction (MS) scheme, is sin
2
ˆ
θ
W
(M
Z
) = 0.231 24(24).
e
The helion, symbol h, is the nucleus of the
3
He atom.
f
This and all other values involving m

τ
are based on the value of m
τ
c
2
in MeV recommended by the Particle Data Group, Caso et al., Eur. Phys.
J. C 3(1-4), 1-794 (1998), but with a standard uncertainty of 0.29 MeV rather than the quoted uncertainty of −0.26 MeV, +0.29 MeV.
g
The numerical value of F to be used in coulometric chemical measurements is 96 485.3432(76) [7.9×10
−8
] when the relevant current ismeasured
in terms of representations of the volt and ohm based on the Josephson and quantum Hall effects and the internationally adopted conventional values
of the Josephson and von Klitzing constants K
J−90
and R
K−90
given in the “Adopted values” table.
h
The entropy of an ideal monoatomic gas of relative atomic mass A
r
is given by S = S
0
+
3
2
R ln A
r
− R ln( p/ p
0
) +

5
2
R ln(T/K).

Fundamental Physical Constants — Adopted values
Relative std.

Quantity Symbol Value Unit uncert. u
r
molar mass of
12
C M(
12
C) 12 × 10
−3
kg mol
−1
(exact)
molar mass constant
a
M(
12
C)/12 M
u
1 × 10
−3
kg mol
−1
(exact)
conventional value of Josephson
constant
b
K
J−90
483597.9 GHz V
−1
(exact)

conventional value of von Klitzing
constant
c
R
K−90
25812.807  (exact)
standard atmosphere 101325 Pa (exact)
standard acceleration of gravity g
n
9.806 65 m s
−2
(exact)
a
TherelativeatomicmassA
r
(X) of particle X with mass m(X) is defined by A
r
(X) = m(X)/m
u
,wherem
u
= m(
12
C)/12 = M
u
/N
A
= 1uis
the atomic mass constant, N
A

is the Avogadro constant, and u is the atomic mass unit. Thus the mass of particle X in u is m(X) = A
r
(X) uandthe
molarmassofXisM(X) = A
r
(X)M
u
.
b
This is the value adopted internationally for realizing representations of the volt using the Josephson effect.
c
This is the value adopted internationally for realizing representations of the ohm using the quantum Hall effect.

Energy Equivalents
Jkgm
−1
Hz
1J (1J) = (1 J)/c
2
= (1 J)/hc = (1 J)/h =
1J 1.112650 056 ×10
−17
kg 5.034117 62(39) ×10
24
m
−1
1.509 19050(12) × 10
33
Hz
1kg (1kg)c
2
= (1kg) = (1 kg)c/ h = (1 kg)c
2
/h =
8.987 551 787 × 10
16

J1kg 4.524439 29(35) × 10
41
m
−1
1.356 39277(11) ×10
50
Hz
1m
−1
(1 m
−1
)hc = (1 m
−1
)h/c = (1m
−1
) = (1 m
−1
)c =
1.986 445 44(16) × 10
−25
J2.210218 63(17) ×10
−42
kg 1 m
−1
299 792458 Hz
1Hz (1Hz)h = (1 Hz)h/c
2
= (1 Hz)/c = (1Hz) =
6.626 068 76(52) × 10
−34

J7.372495 78(58) × 10
−51
kg 3.335 640952 × 10
−9
m
−1
1Hz
1K (1K)k = (1 K)k/c
2
= (1 K)k/ hc = (1 K)k/h =
1.3806503(24) × 10
−23
J1.536 1807(27) ×10
−40
kg 69.503 56(12) m
−1
2.083 6644(36) × 10
10
Hz
1eV (1eV)= (1eV)/c
2
= (1eV)/hc = (1eV)/h =
1.602176 462(63) ×10
−19
J1.782661 731(70) ×10
−36
kg 8.065 54477(32) × 10
5
m
−1

2.417 989 491(95) × 10
14
Hz
1u (1u)c
2
= (1 u) = (1u)c/h = (1u)c
2
/h =
1.492417 78(12) ×10
−10
J1.660538 73(13) × 10
−27
kg 7.513 006 658(57) × 10
14
m
−1
2.252342 733(17) ×10
23
Hz
1 E
h
(1 E
h
) = (1 E
h
)/c
2
= (1 E
h
)/hc = (1 E

h
)/h =
4.359 743 81(34) × 10
−18
J4.850869 19(38) ×10
−35
kg 2.194746 313710(17) × 10
7
m
−1
6.579 683 920735(50) ×10
15
Hz
Derived from the relations E = mc
2
= hc/λ = hν = kT, and based on the 1998 CODATA adjustment of the values of the constants;
1eV= (e/C) J, 1 u = m
u
=
1
12
m(
12
C) = 10
−3
kg mol
−1
/N
A
,andE

h
= 2R
∞
hc = α
2
m
e
c
2
is the Hartree energy (hartree).

Energy Equivalents
KeV u E
h
1J (1J)/k = (1 J) = (1 J)/c
2
=(1J)=
7.242964(13) × 10
22
K6.241 509 74(24) × 10
18
eV 6.700536 62(53) × 10
9
u2.293 71276(18) ×10
17
E
h
1kg (1kg)c
2
/k = (1 kg)c
2
= (1 kg) = (1 kg)c
2
=
6.509 651(11) ×10
39

K5.609 589 21(22) × 10
35
eV 6.022141 99(47) × 10
26
u2.061486 22(16) × 10
34
E
h
1m
−1
(1 m
−1
)hc/k = (1 m
−1
)hc = (1 m
−1
)h/c =(1m
−1
)hc =
1.438 7752(25) ×10
−2
K1.239 841 857(49) × 10
−6
eV 1.331 025042(10) × 10
−15
u4.556 335 252750(35) × 10
−8
E
h
1Hz (1Hz)h/k = (1 Hz)h = (1 Hz)h/c

2
=(1Hz)h =
4.799 2374(84) ×10
−11
K4.135 667 27(16) ×10
−15
eV 4.439821 637(34) × 10
−24
u1.519 829 846 003(12) × 10
−16
E
h
1K (1K) = (1 K)k = (1 K)k/c
2
= (1 K)k =
1K 8.617 342(15) ×10
−5
eV 9.251 098(16) × 10
−14
u3.166 8153(55) × 10
−6
E
h
1eV (1eV)/k = (1eV) = (1eV)/c
2
= (1eV) =
1.1604506(20) ×10
4
K 1 eV 1.073 544206(43) ×10
−9

u3.674932 60(14) × 10
−2
E
h
1u (1u)c
2
/k = (1u)c
2
= (1u) = (1u)c
2
=
1.0809528(19) ×10
13
K 931.494013(37) × 10
6
eV 1 u 3.423 177 709(26) × 10
7
E
h
1 E
h
(1 E
h
)/k = (1 E
h
) = (1 E
h
)/c
2
= (1 E

h
) =
3.157 7465(55) ×10
5
K27.211 3834(11) eV 2.921 262304(22) ×10
−8
u1E
h
Derived from the relations E = mc
2
= hc/λ = hν = kT, and based on the 1998 CODATA adjustment of the values of the constants;
1eV= (e/C) J, 1 u = m
u
=
1
12
m(
12
C) = 10
−3
kg mol
−1
/N
A
,andE
h
= 2R
∞
hc = α
2

m
e
c
2
is the Hartree energy (hartree).

1-12
STANDARD ATOMIC WEIGHTS (1997)
This table of atomic weights is reprinted from the 1997 report of the IUPAC Commission on Atomic Weights and Isotopic Abundances. The
Standard Atomic Weights apply to the elements as they exist naturally on Earth, and the uncertainties take into account the isotopic variation found
in most laboratory samples. Further comments on the variability are given in the footnotes.
The number in parentheses following the atomic weight value gives the uncertainty in the last digit. An entry in brackets indicates the mass number
of the longest-lived isotope of an element that has no stable isotopes and for which a Standard Atomic Weight cannot be defined because of wide
variability in isotopic composition (or complete absence) in nature.
REFERENCE
Vocke, R. D. (for IUPAC Commission on Atomic Weights and Isotopic Abundances), Atomic Weights of the Elements 1997, Pure Appl. Chem., 71,
1593, 1999.
At.
Name Symbol no. Atomic Weight Footnotes
Actinium Ac 89 [227]
Aluminum Al 13 26.981538(2)
Americium Am 95 [243]
Antimony Sb 51 121.760(1) g
Argon Ar 18 39.948(1) g r
Arsenic As 33 74.92160(2)
Astatine At 85 [210]
Barium Ba 56 137.327(7)
Berkelium Bk 97 [247]
Beryllium Be 4 9.012182(3)
Bismuth Bi 83 208.98038(2)
Bohrium Bh 107 [264]
Boron B 5 10.811(7) g m r
Bromine Br 35 79.904(1)
Cadmium Cd 48 112.411(8) g
Calcium Ca 20 40.078(4) g

Californium Cf 98 [251]
Carbon C 6 12.0107(8) g r
Cerium Ce 58 140.116(1) g
Cesium Cs 55 132.90545(2)
Chlorine Cl 17 35.4527(9) m
Chromium Cr 24 51.9961(6)
Cobalt Co 27 58.933200(9)
Copper Cu 29 63.546(3) r
Curium Cm 96 [247]
Dubnium Db 105 [262]
Dysprosium Dy 66 162.50(3) g
Einsteinium Es 99 [252]
Erbium Er 68 167.26(3) g
Europium Eu 63 151.964(1) g
Fermium Fm 100 [257]
Fluorine F 9 18.9984032(5)
Francium Fr 87 [223]
Gadolinium Gd 64 157.25(3) g
Gallium Ga 31 69.723(1)
Germanium Ge 32 72.61(2)
Gold Au 79 196.96655(2)
Hafnium Hf 72 178.49(2)
Hassium Hs 108 [269]
Helium He 2 4.002602(2) g r
Holmium Ho 67 164.93032(2)
Hydrogen H 1 1.00794(7) g m r
Indium In 49 114.818(3)
Iodine I 53 126.90447(3)
1-13
STANDARD ATOMIC WEIGHTS (1997) (continued)

Iridium Ir 77 192.217(3)
Iron Fe 26 55.845(2)
Krypton Kr 36 83.80(1) g m
Lanthanum La 57 138.9055(2) g
Lawrencium Lr 103 [262]
Lead Pb 82 207.2(1) g r
Lithium Li 3 6.941(2)* g m r
Lutetium Lu 71 174.967(1) g
Magnesium Mg 12 24.3050(6)
Manganese Mn 25 54.938049(9)
Meitnerium Mt 109 [268]
Mendelevium Md 101 [258]
Mercury Hg 80 200.59(2)
Molybdenum Mo 42 95.94(1) g
Neodymium Nd 60 144.24(3) g
Neon Ne 10 20.1797(6) g m
Neptunium Np 93 [237]
Nickel Ni 28 58.6934(2)
Niobium Nb 41 92.90638(2)
Nitrogen N 7 14.00674(7) g r
Nobelium No 102 [259]
Osmium Os 76 190.23(3) g
Oxygen O 8 15.9994(3) g r
Palladium Pd 46 106.42(1) g
Phosphorus P 15 30.973761(2)
Platinum Pt 78 195.078(2)
Plutonium Pu 94 [244]
Polonium Po 84 [209]
Potassium K 19 39.0983(1) g
Praseodymium Pr 59 140.90765(2)

Promethium Pm 61 [145]
Protactinium Pa 91 231.03588(2)
Radium Ra 88 [226]
Radon Rn 86 [222]
Rhenium Re 75 186.207(1)
Rhodium Rh 45 102.90550(2)
Rubidium Rb 37 85.4678(3) g
Ruthenium Ru 44 101.07(2) g
Rutherfordium Rf 104 [261]
Samarium Sm 62 150.36(3) g
Scandium Sc 21 44.955910(8)
Seaborgium Sg 106 [266]
Selenium Se 34 78.96(3)
Silicon Si 14 28.0855(3) r
Silver Ag 47 107.8682(2) g
Sodium Na 11 22.989770(2)
Strontium Sr 38 87.62(1) g r
Sulfur S 16 32.066(6) g r
Tantalum Ta 73 180.9479(1)
Technetium Tc 43 [98]
Tellurium Te 52 127.60(3) g
Terbium Tb 65 158.92534(2)
Thallium Tl 81 204.3833(2)
Thorium Th 90 232.0381(1) g
Thulium Tm 69 168.93421(2)
Tin Sn 50 118.710(7) g
Titanium Ti 22 47.867(1)
Tungsten W 74 183.84(1)
At.
Name Symbol no. Atomic Weight Footnotes

1-14
STANDARD ATOMIC WEIGHTS (1997) (continued)
Uranium U 92 238.0289(1) g m
Vanadium V 23 50.9415(1)
Xenon Xe 54 131.29(2) g m
Ytterbium Yb 70 173.04(3) g
Yttrium Y 39 88.90585(2)
Zinc Zn 30 65.39(2)
Zirconium Zr 40 91.224(2) g
At.
Name Symbol no. Atomic Weight Footnotes
* Commercially available Li materials have atomic weights that are known to range between 6.939 and 6.996; if a more accurate value is required,
it must be determined for the specific material.
g geological specimens are known in which the element has an isotopic composition outside the limits for normal material. The difference
between the atomic weight of the element in such specimens and that given in the table may exceed the stated uncertainty.
m modified isotopic compositions may be found in commercially available material because it has been subjected to an undisclosed or inadvertent
isotopic fractionation. Substantial deviations in atomic weight of the element from that given the table can occur.
r range in isotopic composition of normal terrestrial material prevents a more precise atomic weight being given; the tabulated atomic weight
value should be applicable to any normal material.
1-15
ATOMIC MASSES AND ABUNDANCES
This table lists the mass (in atomic mass units, symbol u) and the natural abundance (in percent) of the stable nuclides and a few important radioactive
nuclides. A complete table of all nuclides may be found in Section 11 (“Table of the Isotopes”).
The atomic masses are based on the 1995 evaluation of Audi and Wapstra (Reference 2). The number in parentheses following the mass value is
the uncertainty in the last digit(s) given.
Natural abundance values are also followed by uncertainties in the last digit(s) of the stated values. This uncertainty includes both the estimated
measurement uncertainty and the reported range of variation in different terrestrial sources of the element (see Reference 3 and 4 for more details).
The absence of an entry in the Abundance column indicates a radioactive nuclide not present in nature or an element whose isotopic composition varies
so widely that a meaningful natural abundance cannot be defined.
An electronic version of these data is available on the Web site of the NIST Physics Laboratory (Reference 5).

REFERENCES
1. Holden, N. E., “Table of the Isotopes”, in Lide, D. R., Ed., CRC Handbook of Chemistry and Physics, 82nd Ed., CRC Press, Boca Raton FL,
2001.
2. Audi, G., and Wapstra, A. H., Nucl. Phys., A595, 409, 1995.
3. Rosman, K. J. R., and Taylor, P. D. P., J. Phys. Chem. Ref. Data, 27, 1275, 1998.
4. R. D. Vocke (for IUPAC Commission on Atomic Weights and Isotopic Abundances), Pure Appl. Chem., 71, 1593, 1999.
5. Coursey, J. S., and Dragoset, R. A., Atomic Weights and Isotopic Compositions (version 2.1). Available: />National Institute of Standards and Technology, Gaithersburg, MD.
1
1
H 1.0078250321(4) 99.9850(70)
2
D 2.0141017780(4) 0.0115(70)
3
T 3.0160492675(11)
2
3
He 3.0160293097(9) 0.000137(3)
4
He 4.0026032497(10) 99.999863(3)
3
6
Li 6.0151223(5) 7.59(4)
7
Li 7.0160040(5) 92.41(4)
4
9
Be 9.0121821(4) 100
5
10
B 10.0129370(4) 19.9(7)

11
B 11.0093055(5) 80.1(7)
6
12
C 12.0000000(0) 98.93(8)
13
C 13.0033548378(10) 1.07(8)
7
14
N 14.0030740052(9) 99.632(7)
15
N 15.0001088984(9) 0.368(7)
8
16
O 15.9949146221(15) 99.757(16)
17
O 16.99913150(22) 0.038(1)
18
O 17.9991604(9) 0.205(14)
9
19
F 18.99840320(7) 100
10
20
Ne 19.9924401759(20) 90.48(3)
21
Ne 20.99384674(4) 0.27(1)
22
Ne 21.99138551(23) 9.25(3)
11

23
Na 22.98976967(23) 100
12
24
Mg 23.98504190(20) 78.99(4)
25
Mg 24.98583702(20) 10.00(1)
26
Mg 25.98259304(21) 11.01(3)
13
27
Al 26.98153844(14) 100
14
28
Si 27.9769265327(20) 92.2297(7)
29
Si 28.97649472(3) 4.6832(5)
30
Si 29.97377022(5) 3.0872(5)
15
31
P 30.97376151(20) 100
16
32
S 31.97207069(12) 94.93(31)
33
S 32.97145850(12) 0.76(2)
34
S 33.96786683(11) 4.29(28)
36

S 35.96708088(25) 0.02(1)
17
35
Cl 34.96885271(4) 75.78(4)
37
Cl 36.96590260(5) 24.22(4)
18
36
Ar 35.96754628(27) 0.3365(30)
38
Ar 37.9627322(5) 0.0632(5)
40
Ar 39.962383123(3) 99.6003(30)
19
39
K 38.9637069(3) 93.2581(44)
40
K 39.96399867(29) 0.0117(1)
41
K 40.96182597(28) 6.7302(44)
20
40
Ca 39.9625912(3) 96.941(156)
42
Ca 41.9586183(4) 0.647(23)
43
Ca 42.9587668(5) 0.135(10)
44
Ca 43.9554811(9) 2.086(110)
46

Ca 45.9536928(25) 0.004(3)
48
Ca 47.952534(4) 0.187(21)
21
45
Sc 44.9559102(12) 100
22
46
Ti 45.9526295(12) 8.25(3)
47
Ti 46.9517638(10) 7.44(2)
48
Ti 47.9479471(10) 73.72(3)
49
Ti 48.9478708(10) 5.41(2)
50
Ti 49.9447921(11) 5.18(2)
23
50
V 49.9471628(14) 0.250(4)
51
V 50.9439637(14) 99.750(4)
24
50
Cr 49.9460496(14) 4.345(13)
52
Cr 51.9405119(15) 83.789(18)
53
Cr 52.9406538(15) 9.501(17)
54

Cr 53.9388849(15) 2.365(7)
25
55
Mn 54.9380496(14) 100
26
54
Fe 53.9396148(14) 5.845(35)
56
Fe 55.9349421(15) 91.754(36)
57
Fe 56.9353987(15) 2.119(10)
58
Fe 57.9332805(15) 0.282(4)
27
59
Co 58.9332002(15) 100
28
58
Ni 57.9353479(15) 68.0769(89)
60
Ni 59.9307906(15) 26.2231(77)
61
Ni 60.9310604(15) 1.1399(6)
62
Ni 61.9283488(15) 3.6345(17)
64
Ni 63.9279696(16) 0.9256(9)
29
63
Cu 62.9296011(15) 69.17(3)

65
Cu 64.9277937(19) 30.83(3)
30
64
Zn 63.9291466(18) 48.63(60)
66
Zn 65.9260368(16) 27.90(27)
67
Zn 66.9271309(17) 4.10(13)
Z Isotope Mass in u Abundance in % Z Isotope Mass in u Abundance in %
1-16
106
Pd 105.903483(5) 27.33(3)
108
Pd 107.903894(4) 26.46(9)
110
Pd 109.905152(12) 11.72(9)
47
107
Ag 106.905093(6) 51.839(8)
109
Ag 108.904756(3) 48.161(8)
48
106
Cd 105.906458(6) 1.25(6)
108
Cd 107.904183(6) 0.89(3)
110
Cd 109.903006(3) 12.49(18)
111

Cd 110.904182(3) 12.80(12)
112
Cd 111.9027572(30) 24.13(21)
113
Cd 112.9044009(30) 12.22(12)
114
Cd 113.9033581(30) 28.73(42)
116
Cd 115.904755(3) 7.49(18)
49
113
In 112.904061(4) 4.29(5)
115
In 114.903878(5) 95.71(5)
50
112
Sn 111.904821(5) 0.97(1)
114
Sn 113.902782(3) 0.66(1)
115
Sn 114.903346(3) 0.34(1)
116
Sn 115.901744(3) 14.54(9)
117
Sn 116.902954(3) 7.68(7)
118
Sn 117.901606(3) 24.22(9)
119
Sn 118.903309(3) 8.59(4)
120

Sn 119.9021966(27) 32.58(9)
122
Sn 121.9034401(29) 4.63(3)
124
Sn 123.9052746(15) 5.79(5)
51
121
Sb 120.9038180(24) 57.21(5)
123
Sb 122.9042157(22) 42.79(5)
52
120
Te 119.904020(11) 0.09(1)
122
Te 121.9030471(20) 2.55(12)
123
Te 122.9042730(19) 0.89(3)
124
Te 123.9028195(16) 4.74(14)
125
Te 124.9044247(20) 7.07(15)
126
Te 125.9033055(20) 18.84(25)
128
Te 127.9044614(19) 31.74(8)
130
Te 129.9062228(21) 34.08(62)
53
127
I 126.904468(4) 100

54
124
Xe 123.9058958(21) 0.09(1)
126
Xe 125.904269(7) 0.09(1)
128
Xe 127.9035304(15) 1.92(3)
129
Xe 128.9047795(9) 26.44(24)
130
Xe 129.9035079(10) 4.08(2)
131
Xe 130.9050819(10) 21.18(3)
132
Xe 131.9041545(12) 26.89(6)
134
Xe 133.9053945(9) 10.44(10)
136
Xe 135.907220(8) 8.87(16)
55
133
Cs 132.905447(3) 100
56
130
Ba 129.906310(7) 0.106(1)
132
Ba 131.905056(3) 0.101(1)
134
Ba 133.904503(3) 2.417(18)
135

Ba 134.905683(3) 6.592(12)
136
Ba 135.904570(3) 7.854(24)
137
Ba 136.905821(3) 11.232(24)
138
Ba 137.905241(3) 71.698(42)
57
138
La 137.907107(4) 0.090(1)
139
La 138.906348(3) 99.910(1)
58
136
Ce 135.907140(50) 0.185(2)
138
Ce 137.905986(11) 0.251(2)
140
Ce 139.905434(3) 88.450(51)
68
Zn 67.9248476(17) 18.75(51)
70
Zn 69.925325(4) 0.62(3)
31
69
Ga 68.925581(3) 60.108(9)
71
Ga 70.9247050(19) 39.892(9)
32
70

Ge 69.9242504(19) 20.84(87)
72
Ge 71.9220762(16) 27.54(34)
73
Ge 72.9234594(16) 7.73(5)
74
Ge 73.9211782(16) 36.28(73)
76
Ge 75.9214027(16) 7.61(38)
33
75
As 74.9215964(18) 100
34
74
Se 73.9224766(16) 0.89(4)
76
Se 75.9192141(16) 9.37(29)
77
Se 76.9199146(16) 7.63(16)
78
Se 77.9173095(16) 23.77(28)
80
Se 79.9165218(20) 49.61(41)
82
Se 81.9167000(22) 8.73(22)
35
79
Br 78.9183376(20) 50.69(7)
81
Br 80.916291(3) 49.31(7)

36
78
Kr 77.920386(7) 0.35(1)
80
Kr 79.916378(4) 2.28(6)
82
Kr 81.9134846(28) 11.58(14)
83
Kr 82.914136(3) 11.49(6)
84
Kr 83.911507(3) 57.00(4)
86
Kr 85.9106103(12) 17.30(22)
37
85
Rb 84.9117893(25) 72.17(2)
87
Rb 86.9091835(27) 27.83(2)
38
84
Sr 83.913425(4) 0.56(1)
86
Sr 85.9092624(24) 9.86(1)
87
Sr 86.9088793(24) 7.00(1)
88
Sr 87.9056143(24) 82.58(1)
39
89
Y 88.9058479(25) 100

40
90
Zr 89.9047037(23) 51.45(40)
91
Zr 90.9056450(23) 11.22(5)
92
Zr 91.9050401(23) 17.15(8)
94
Zr 93.9063158(25) 17.38(28)
96
Zr 95.908276(3) 2.80(9)
41
93
Nb 92.9063775(24) 100
42
92
Mo 91.906810(4) 14.84(35)
94
Mo 93.9050876(20) 9.25(12)
95
Mo 94.9058415(20) 15.92(13)
96
Mo 95.9046789(20) 16.68(2)
97
Mo 96.9060210(20) 9.55(8)
98
Mo 97.9054078(20) 24.13(31)
100
Mo 99.907477(6) 9.63(23)
43

97
Tc 96.906365(5)
98
Tc 97.907216(4)
99
Tc 98.9062546(21)
44
96
Ru 95.907598(8) 5.54(14)
98
Ru 97.905287(7) 1.87(3)
99
Ru 98.9059393(21) 12.76(14)
100
Ru 99.9042197(22) 12.60(7)
101
Ru 100.9055822(22) 17.06(2)
102
Ru 101.9043495(22) 31.55(14)
104
Ru 103.905430(4) 18.62(27)
45
103
Rh 102.905504(3) 100
46
102
Pd 101.905608(3) 1.02(1)
104
Pd 103.904035(5) 11.14(8)
105

Pd 104.905084(5) 22.33(8)
ATOMIC MASSES AND ABUNDANCES (continued)
Z Isotope Mass in u Abundance in % Z Isotope Mass in u Abundance in %
1-17
142
Ce 141.909240(4) 11.114(51)
59
141
Pr 140.907648(3) 100
60
142
Nd 141.907719(3) 27.2(5)
143
Nd 142.909810(3) 12.2(2)
144
Nd 143.910083(3) 23.8(3)
145
Nd 144.912569(3) 8.3(1)
146
Nd 145.913112(3) 17.2(3)
148
Nd 147.916889(3) 5.7(1)
150
Nd 149.920887(4) 5.6(2)
61
145
Pm 144.912744(4)
147
Pm 146.915134(3)
62

144
Sm 143.911995(4) 3.07(7)
147
Sm 146.914893(3) 14.99(18)
148
Sm 147.914818(3) 11.24(10)
149
Sm 148.917180(3) 13.82(7)
150
Sm 149.917271(3) 7.38(1)
152
Sm 151.919728(3) 26.75(16)
154
Sm 153.922205(3) 22.75(29)
63
151
Eu 150.919846(3) 47.81(3)
153
Eu 152.921226(3) 52.19(3)
64
152
Gd 151.919788(3) 0.20(1)
154
Gd 153.920862(3) 2.18(3)
155
Gd 154.922619(3) 14.80(12)
156
Gd 155.922120(3) 20.47(9)
157
Gd 156.923957(3) 15.65(2)

158
Gd 157.924101(3) 24.84(7)
160
Gd 159.927051(3) 21.86(19)
65
159
Tb 158.925343(3) 100
66
156
Dy 155.924278(7) 0.06(1)
158
Dy 157.924405(4) 0.10(1)
160
Dy 159.925194(3) 2.34(8)
161
Dy 160.926930(3) 18.91(24)
162
Dy 161.926795(3) 25.51(26)
163
Dy 162.928728(3) 24.90(16)
164
Dy 163.929171(3) 28.18(37)
67
165
Ho 164.930319(3) 100
68
162
Er 161.928775(4) 0.14(1)
164
Er 163.929197(4) 1.61(3)

166
Er 165.930290(3) 33.61(35)
167
Er 166.932045(3) 22.93(17)
168
Er 167.932368(3) 26.78(26)
170
Er 169.935460(3) 14.93(27)
69
169
Tm 168.934211(3) 100
70
168
Yb 167.933894(5) 0.13(1)
170
Yb 169.934759(3) 3.04(15)
171
Yb 170.936322(3) 14.28(57)
172
Yb 171.9363777(30) 21.83(67)
173
Yb 172.9382068(30) 16.13(27)
174
Yb 173.9388581(30) 31.83(92)
176
Yb 175.942568(3) 12.76(41)
71
175
Lu 174.9407679(28) 97.41(2)
176

Lu 175.9426824(28) 2.59(2)
72
174
Hf 173.940040(3) 0.16(1)
176
Hf 175.9414018(29) 5.26(7)
177
Hf 176.9432200(27) 18.60(9)
178
Hf 177.9436977(27) 27.28(7)
179
Hf 178.9458151(27) 13.62(2)
180
Hf 179.9465488(27) 35.08(16)
73
180
Ta 179.947466(3) 0.012(2)
181
Ta 180.947996(3) 99.988(2)
74
180
W 179.946706(5) 0.12(1)
182
W 181.948206(3) 26.50(16)
183
W 182.9502245(29) 14.31(4)
184
W 183.9509326(29) 30.64(2)
186
W 185.954362(3) 28.43(19)

75
185
Re 184.9529557(30) 37.40(2)
187
Re 186.9557508(30) 62.60(2)
76
184
Os 183.952491(3) 0.02(1)
186
Os 185.953838(3) 1.59(3)
187
Os 186.9557479(30) 1.96(2)
188
Os 187.9558360(30) 13.24(8)
189
Os 188.9581449(30) 16.15(5)
190
Os 189.958445(3) 26.26(2)
192
Os 191.961479(4) 40.78(19)
77
191
Ir 190.960591(3) 37.3(2)
193
Ir 192.962924(3) 62.7(2)
78
190
Pt 189.959930(7) 0.014(1)
192
Pt 191.961035(4) 0.782(7)

194
Pt 193.962664(3) 32.967(99)
195
Pt 194.964774(3) 33.832(10)
196
Pt 195.964935(3) 25.242(41)
198
Pt 197.967876(4) 7.163(55)
79
197
Au 196.966552(3) 100
80
196
Hg 195.965815(4) 0.15(1)
198
Hg 197.966752(3) 9.97(20)
199
Hg 198.968262(3) 16.87(22)
200
Hg 199.968309(3) 23.10(19)
201
Hg 200.970285(3) 13.18(9)
202
Hg 201.970626(3) 29.86(26)
204
Hg 203.973476(3) 6.87(15)
81
203
Tl 202.972329(3) 29.524(14)
205

Tl 204.974412(3) 70.476(14)
82
204
Pb 203.973029(3) 1.4(1)
206
Pb 205.974449(3) 24.1(1)
207
Pb 206.975881(3) 22.1(1)
208
Pb 207.976636(3) 52.4(1)
83
209
Bi 208.980383(3) 100
84
209
Po 208.982416(3)
210
Po 209.982857(3)
85
210
At 209.987131(9)
211
At 210.987481(4)
86
211
Rn 210.990585(8)
220
Rn 220.0113841(29)
222
Rn 222.0175705(27)

87
223
Fr 223.0197307(29)
88
223
Ra 223.018497(3)
224
Ra 224.0202020(29)
226
Ra 226.0254026(27)
228
Ra 228.0310641(27)
89
227
Ac 227.0277470(29)
90
230
Th 230.0331266(22)
232
Th 232.0380504(22) 100
91
231
Pa 231.0358789(28) 100
92
233
U 233.039628(3)
234
U 234.0409456(21) 0.0055(2)
235
U 235.0439231(21) 0.7200(51)

ATOMIC MASSES AND ABUNDANCES (continued)
Z Isotope Mass in u Abundance in % Z Isotope Mass in u Abundance in %
1-18
236
U 236.0455619(21)
238
U 238.0507826(21) 99.2745(106)
93
237
Np 237.0481673(21)
239
Np 239.0529314(23)
94
238
Pu 238.0495534(21)
239
Pu 239.0521565(21)
240
Pu 240.0538075(21)
241
Pu 241.0568453(21)
242
Pu 242.0587368(21)
244
Pu 244.064198(5)
95
241
Am 241.0568229(21)
243
Am 243.0613727(23)

96
243
Cm 243.0613822(24)
244
Cm 244.0627463(21)
245
Cm 245.0654856(29)
246
Cm 246.0672176(24)
247
Cm 247.070347(5)
248
Cm 248.072342(5)
97
247
Bk 247.070299(6)
ATOMIC MASSES AND ABUNDANCES (continued)
Z Isotope Mass in u Abundance in % Z Isotope Mass in u Abundance in %
249
Bk 249.074980(3)
98
249
Cf 249.074847(3)
250
Cf 250.0764000(24)
251
Cf 251.079580(5)
252
Cf 252.081620(5)
99

252
Es 252.082970(50)
100
257
Fm 257.095099(7)
101
256
Md 256.094050(60)
258
Md 258.098425(5)
102
259
No 259.101020(110)*
103
262
Lr 262.109690(320)*
104
261
Rf 261.108750(110)*
105
262
Db 262.114150(200)*
106
263
Sg 263.118310(130)*
107
264
Bh 264.124730(300)*
108
265

Hs 265.130000(320)*
109
268
Mt 268.138820(340)*
110
269
Uun 269.145140(310)*
111
272
Uuu 272.153480(360)*
*Mass values derived not purely from experimental data, but at least partly from systematic trends.
1-13
ELECTRON CONFIGURATION OF NEUTRAL ATOMS IN THE GROUND STATE
KL M N O P Q
Atomic n =1 2 3 4 5 6 7
no. Element s s p s p d s p d f s p d f s p d s
1H 1
2He 2
3Li 21
4Be 22
5B 221
6C 222
7N 223
8O 224
9F 225
10 Ne 2 2 6
11 Na 2 2 6 1
12 Mg 2 2 6 2
13 Al 2 2 6 2 1
14 Si 2 2 6 2 2

15 P 2 2 6 2 3
16 S 2 2 6 2 4
17 Cl 2 2 6 2 5
18 Ar 2 2 6 2 6
19 K 2 2 6 2 6 1
20 Ca 2 2 6 2 6 2
21 Sc 2 2 6 2 6 1 2
22 Ti 2 2 6 2 6 2 2
23 V 2 2 6 2 6 3 2
24 Cr 2 2 6 2 6 5* 1
25 Mn 2 2 6 2 6 5 2
26 Fe 2 2 6 2 6 6 2
27 Co 2 2 6 2 6 7 2
28 Ni 2 2 6 2 6 8 2
29 Cu 2 2 6 2 6 10* 1
30 Zn 2 2 6 2 6 10 2
31 Ga 2 2 6 2 6 10 2 1
32 Ge 2 2 6 2 6 10 2 2
33 As 2 2 6 2 6 10 2 3
34 Se 2 2 6 2 6 10 2 4
35 Br 2 2 6 2 6 10 2 5
36 Kr 2 2 6 2 6 10 2 6
37 Rb 2 2 6 2 6 10 2 6 1
38 Sr 2 2 6 2 6 10 2 6 2
39 Y 2 2 6 2 6 10 2 6 1 2
40 Zr 2 2 6 2 6 10 2 6 2 2
41 Nb 2 2 6 2 6 10 2 6 4* 1
42 Mo 2 2 6 2 6 10 2 6 5 1
43 Tc 2 2 6 2 6 10 2 6 5 2
44 Ru 2 2 6 2 6 10 2 6 7 1

45 Rh 2 2 6 2 6 10 2 6 8 1
46 Pd 2 2 6 2 6 10 2 6 10*
47 Ag 2 2 6 2 6 10 2 6 10 1
48 Cd 2 2 6 2 6 10 2 6 10 2
49 In 2 2 6 2 6 10 2 6 10 2 1
50 Sn 2 2 6 2 6 10 2 6 10 2 2
51 Sb 2 2 6 2 6 10 2 6 10 2 3
52 Te 2 2 6 2 6 10 2 6 10 2 4
53 I 2 2 6 2 6 10 2 6 10 2 5
54 Xe 2 2 6 2 6 10 2 6 10 2 6
55 Cs 2 2 6 2 6 10 2 6 10 2 6 1
56 Ba 2 2 6 2 6 10 2 6 10 2 6 2
1-14
ELECTRON CONFIGURATION OF NEUTRAL ATOMS IN THE GROUND STATE (continued)
KL M N O P Q
Atomic n =1 2 3 4 5 6 7
no. Element s s p s p d s p d f s p d f s p d s
REFERENCE
57 La 2 2 6 2 6 10 2 6 10 2 6 1 2
58 Ce 2 2 6 2 6 10 2 6 10 1* 2 6 1 2
59 Pr 2 2 6 2 610 2 610 3 26 2
60 Nd 2 2 6 2 610 2 610 4 26 2
61 Pm 2 2 6 2 610 2 610 5 26 2
62 Sm 2 2 6 2 610 2 610 6 26 2
63 Eu 2 2 6 2 610 2 610 7 26 2
64 Gd 2 2 6 2 610 2 610 7 26 1 2
65 Tb 2 2 6 2 6 10 2 6 10 9* 2 6 2
66 Dy 2 2 6 2 6 10 2 6 10 10 2 6 2
67 Ho 2 2 6 2 6 10 2 6 10 11 2 6 2
68 Er 2 2 6 2 6 10 2 6 10 12 2 6 2

69 Tm 2 2 6 2 6 10 2 6 10 13 2 6 2
70 Yb 2 2 6 2 6 10 2 6 10 14 2 6 2
71 Lu 2 2 6 2 6 10 2 6 10 14 2 6 1 2
72 Hf 2 2 6 2 6 10 2 6 10 14 2 6 2 2
73 Ta 2 2 6 2 6 10 2 6 10 14 2 6 3 2
74 W 2 2 6 2 6 10 2 6 10 14 2 6 4 2
75 Re 2 2 6 2 6 10 2 6 10 14 2 6 5 2
76 Os 2 2 6 2 6 10 2 6 10 14 2 6 6 2
77 Ir 2 2 6 2 6 10 2 6 10 14 2 6 7 2
78 Pt 2 2 6 2 6 10 2 6 10 14 2 6 9 1
79 Au 2 2 6 2 6 10 2 6 10 14 2 6 10 1
80 Hg 2 2 6 2 6 10 2 6 10 14 2 6 10 2
81 Tl 2 2 6 2 6 10 2 6 10 14 2 6 10 2 1
82 Pb 2 2 6 2 6 10 2 6 10 14 2 6 10 2 2
83 Bi 2 2 6 2 6 10 2 6 10 14 2 6 10 2 3
84 Po 2 2 6 2 6 10 2 6 10 14 2 6 10 2 4
85 At 2 2 6 2 6 10 2 6 10 14 2 6 10 2 5
86 Rn 2 2 6 2 6 10 2 6 10 14 2 6 10 2 6
87 Fr 2 2 6 2 6 10 2 6 10 14 2 6 10 2 6 1
88 Ra 2 2 6 2 6 10 2 6 10 14 2 6 10 2 6 2
89 Ac 2 2 6 2 610 2 610 14 26 10 2612
90 Th 2 2 6 2 610 2 610 14 26 10 2622
91 Pa 2 2 6 2 610 2 610 14 26 10 2* 2612
92 U 2 2 6 2 610 2 610 14 26 10 3 2612
93 Np 2 2 6 2 610 2 610 14 26 10 4 2612
94 Pu 2 2 6 2 6 10 2 6 10 14 2 6 10 6* 2 6 2
95 Am 2 2 6 2 6 10 2 6 10 14 2 6 10 7 2 6 2
96 Cm 2 2 6 2 610 2 610 14 26 10 7* 2612
97 Bk 2 2 6 2 6 10 2 6 10 14 2 6 10 9 2 6 2
98 Cf 2 2 6 2 6 10 2 6 10 14 2 6 10 10 2 6 2

99 Es 2 2 6 2 6 10 2 6 10 14 2 6 10 11 2 6 2
100 Fm 226 261026101426101226 2
101 Md 226 261026101426101326 2
102 No 226 261026101426101426 2
103 Lr 2 2 6 2 610 2 610 14 26 1014 2612
104 Rf 2 2 6 2 610 2 610 14 26 1014 2622
* Note irregularity.
W. L. Wiese and G. A. Martin, in A Physicist’s Desk Reference, American Institute of Physics, New York, 1989, 94.
1-15
INTERNATIONAL TEMPERATURE SCALE OF 1990 (ITS-90)
B. W. Mangum
A new temperature scale, the International Temperature Scale of 1990 (ITS-90), was officially adopted by the Comité International des
Poids et Mesures (CIPM), meeting 26—28 September 1989 at the Bureau International des Poids et Mesures (BIPM). The ITS-90 was recommended
to the CIPM for its adoption following the completion of the final details of the new scale by the Comité Consultatif de Thermométrie (CCT), meeting
12—14 September 1989 at the BIPM in its 17th Session. The ITS-90 became the official international temperature scale on 1 January 1990. The ITS-
90 supersedes the present scales, the International Practical Temperature Scale of 1968 (IPTS-68) and the 1976 Provisional 0.5 to 30 K Temperature
Scale (EPT-76).
The ITS-90 extends upward from 0.65 K, and temperatures on this scale are in much better agreement with thermodynamic values that are
those on the IPTS-68 and the EPT-76. The new scale has subranges and alternative definitions in certain ranges that greatly facilitate its use.
Furthermore, its continuity, precision, and reproducibility throughout its ranges are much improved over that of the present scales. The replacement
of the thermocouple with the platinum resistance thermometer at temperatures below 961.78°C resulted in the biggest improvement in reproducibility.
The ITS-90 is divided into four primary ranges:
1. Between 0.65 and 3.2 K, the ITS-90 is defined by the vapor pressure-temperature relation of
3
He, and between 1.25 and 2.1768 K (the λ point)
and between 2.1768 and 5.0 K by the vapor pressure-temperature relations of
4
He. T
90
is defined by the vapor pressure equations of the form:

The values of the coefficients A
i
, and of the constants A
o
, B, and C of the equations are given below.
2. Between 3.0 and 24.5561 K, the ITS-90 is defined in terms of a
3
He or
4
He constant volume gas thermometer (CVGT). The thermometer is
calibrated at three temperatures — at the triple point of neon (24.5561 K), at the triple point of equilibrium hydrogen (13.8033 K), and at a
temperature between 3.0 and 5.0 K, the value of which is determined by using either
3
He or
4
He vapor pressure thermometry.
3. Between 13.8033 K (–259.3467°C) and 1234.93 K (961.78°C), the ITS-90 is defined in terms of the specified fixed points given below, by
resistance ratios of platinum resistance thermometers obtained by calibration at specified sets of the fixed points, and by reference functions
and deviation functions of resistance ratios which relate to T
90
between the fixed points.
4. Above 1234.93 K, the ITS-90 is defined in terms of Planck’s radiation law, using the freezing-point temperature of either silver, gold, or copper
as the reference temperature.
Full details of the calibration procedures and reference functions for various subranges are given in:
The International Temperature Scale of 1990, Metrologia, 27, 3, 1990; errata in Metrologia, 27, 107, 1990.
Defining Fixed Points of the ITS-90
Material
a
Equilibrium state
b

Temperature
T
90
(K) t
90
(°C)
He VP 3 to 5 –270.15 to –268.15
e-H
2
TP 13.8033 –259.3467
e-H
2
(or He) VP (or CVGT) ≈17 ≈ –256.15
e-H
2
(or He) VP (or CVGT) ≈20.3 ≈ –252.85
Ne
c
TP 24.5561 –248.5939
O
2
TP 54.3584 –218.7916
Ar TP 83.8058 –189.3442
Hg
c
TP 234.3156 –38.8344
H
2
O TP 273.16 0.01
Ga

c
MP 302.9146 29.7646
In
c
FP 429.7485 156.5985
Sn FP 505.078 231.928
Zn FP 692.677 419.527
Al
c
FP 933.473 660.323
Ag FP 1234.93 961.78
Au FP 1337.33 1064.18
Cu
c
FP 1357.77 1084.62
T/ A A p/ –B/C
i
90 0
1
9
KPa
i
i
=+
()
()
[]
=
∑
ln

1-16
INTERNATIONAL TEMPERATURE SCALE OF 1990 (ITS-90) (continued)
Defining Fixed Points of the ITS-90 (continued)
a
e-H
2
indicates equilibrium hydrogen, that is, hydrogen with the equilibrium distribution of its ortho and para states. Normal
hydrogen at room temperature contains 25% para hydrogen and 75% ortho hydrogen.
b
VP indicates vapor pressure point; CVGT indicates constant volume gas thermometer point; TP indicates triple point
(equilibrium temperature at which the solid, liquid, and vapor phases coexist); FP indicates freezing point, and MP indicates
melting point (the equilibrium temperatures at which the solid and liquid phases coexist under a pressure of 101 325 Pa, one
standard atmosphere). The isotopic composition is that naturally occurring.
c
Previously, these were secondary fixed points.
Values of Coefficients in the Vapor Pressure Equations for Helium
Coef.or
3
He
4
He
4
He
constant 0.65—3.2 K 1.25—2.1768 K 2.1768—5.0 K
A
0
1.053 447 1.392 408 3.146 631
A
1
0.980 106 0.527 153 1.357 655

A
2
0.676 380 0.166 756 0.413 923
A
3
0.372 692 0.050 988 0.091 159
A
4
0.151 656 0.026 514 0.016 349
A
5
–0.002 263 0.001 975 0.001 826
A
6
0.006 596 –0.017 976 –0.004 325
A
7
0.088 966 0.005 409 –0.004 973
A
8
–0.004 770 0.013 259 0
A
9
–0.054 943 0 0
B 7.3 5.6 10.3
C 4.3 2.9 1.9