Aston 1922
ISOTOPES[1]
F. W. ASTON, M.A., D.Sc, A.I.C., F.R.S.
Fellow of Trinity College, Cambridge
LONDON
EDWARD. ARNOLD & CO.
1922
[All rights reserved]
Printed in Great Britain
PREFACE
I have undertaken the preparation of this book on isotopes in response to many requests made to me by teachers of physics and chemistry and others working in these subjects that I should publish the results obtained by means of the mass spectrograph in a form more convenient to the public than that in which they first appeared. This is one of the reasons why the space allotted to the inactive isotopes may appear, in the light of the general title of the book, somewhat disproportion- ately large. Another is that the subject of radioactive isotopes really requires a book to itself, and I am in the hope that the inadequacy of my account may stimulate the production of such a volume by hands more competent than mine to deal with this very special and remarkable field of modern science. The logical order of exposition of a scientific subject is to start with the simple and from that build up the more complex. Unfortunately the sequence of events in experimental research is the exact opposite of this so that a compromise must be effected, unless one is content to sacrifice historical treatment altogether. The latter seems very undesirable in a new subject. I have endeavoured in Chapters I, II and IV, and elsewhere when possible, to adhere strictly to the historical order of events even at the cost of some reiteration.
I wish to take this opportunity of expressing my indebted- ness to Mr. C. G. Darwin for his timely criticism and unfailing assistance throughout the work, and also to Mr. R. H. Fowler for help with the proofs. My thanks are also due to Professor Soddy for his diagram of the radioactive isotopes, to Mr. A. J. Dempster for kindly sending me the illustrations of his work, to the proprietors of the Philosophical Magazine and to the Council of the Chemical Society for permission to use the plates and figures of my original papers, and to Messrs. Macmillan & Co., for the diagram of the radioactive trans- formations.
- F. W. Aston
- Cambridge,
- January, 1922.
CONTENTS
CHAPTER I - INTRODUCTION
CHAPTER II - THE RADIOACTIVE ISOTOPES
CHAPTER III - POSITIVE RAYS
CHAPTER IV - NEON
CHAPTER V - THE MASS-SPECTROGRAPH
CHAPTER VI - ANALYSIS OF THE ELEMENTS
CHAPTER VII - ANALYSIS OF THE ELEMENTS (Continued)
CHAPTER VIII - THE ELECTRICAL THEORY OF MATTER
CHAPTER IX - ISOTOPES AND ATOMIC NUMBERS
CHAPTER X - THE SPECTRA OF ISOTOPES
CHAPTER XI - THE SEPARATION OF ISOTOPES
APPENDIX I
APPENDIX II
The Periodic Table of the Elements. The atomic numbers ar= e given in bold type, the atomic weights in italics and the isotopes, where = known, in ordinary numerals. The roman ntmierals indicate the chemical groups and the most important associated valencies are given below them. Elem= ents are placed to the left or to the right of the columns according= to their chemical properties, those in the same vertical line as each other have s= trong chemical similarities. The Rare Earth group is surrounded by a thick line.= Elements 59-72 have no properties pronounced enough to give them definite = places in the table. The properties of the missing elements can be p= redicted with
PERIODIC TABLE OF
IH
1-008
Valency
0
I
+ 1
II
+ 2
III
+ 3
IV
+ 4
2 He
4-00 4
3 Li
6-94 6, 7
4 Be
9-1
9
5B 10-9 10, 11
60
12-00 12
10 Ne
20-2 20, 22
11 Na
23-00 23
12 Mg
24-32
24, 25, 26
13 AI
26-96
14 Si 28-3 28,29
18 A
39-9 36, 40
19 K
39-1 39, 41
29 Cu
63-57
20 Ca
40-07
30 Zn
65-37
21 Sc 45-1
31 G
70-1
22 Ti 48-1
32 Ge
72-5
36 Kr
82-92
78, 80, 82, 83, 84, 86
37 Rb
85-45
85, 87
47 Ag 107-88
38 Sr
87-83
48 Cd 112-40
39 Y
89-33
49 In
114-8
40 Zr
90-6
50 Sn
118-7
54 Xe
130-2
129, 131, 132, 134, 136
55 Cs
132-81
133
56 Ba
137-37
57 La 58 Ce 139-0 140-25
59 Pr eONd 61 62 Sm 63 Eu =
64 Gd 65 Tb
140-6 144-3 150-4 152-0 =
157-3 159-2
66 Ds 67 Ho 68 Ev 69 Tu 70 Yb 7= 1 Lu 72 (Kt) 162-5 163-5 1677 168-5 173-5 =
175
79 Au
197-2
80 Hg
200-6 197-204
81 Tl
204-0
82 Pb
207-2
86 Em
222-0
87-
88 Ra
226-0
89 Ac
90 Th
232-15
144
considerable certainty from the positions of their atomic numbers. From the point of view of the construction of the atom the inert gas= es should mark the end of the periods as they are shown to do ua the hst of = atomic weights in Appendix I, on the other hand it is more usual in chemistry = to start with valency 0. From principles of general convenience of arrangement t= he latter plan is adopted in this table, which is intended to give = the maximum amount of chemical information. Hydrogen, which belongs equally wel= l to group I or group VII, is best omitted from the. table altoget= her.
THE ELEMENTS
V
VI
VII
VIII
3
2
-
-1
7N
80
9F
14-01
16-00
1900
14
16
19
15 P
16 S
17 CI
31-04
32-06
35-46
31
32
35, 37
23 V
24 Cr
25 Mn
26 Fe
27 Co
28 Ni
Sl-O
33 As
74-96 75
52-0
34 Se
79-2
54-93
35 Br
79-92 79, 81
55-85
58-97
58-68 58.60
41 Nb
42 Mo
43
44 Ru
45 Rh
46 Pd
93-5
51 Sb 120-2
96-0
52 Te 127-5
531
126-92 127
101-7
102-9
106-7
73 Ta
74 W
7&-
76 0a
77 Ir
78 Pt
181-5
83 Bi
209-0
184-0
84 Po
85
190-9
1931
195-2
91 UX
ii
92 U
238-2
145
Recent results obtained by Dempster. Thanks to a private=
communication the writer is able to include some further results=
obtained by Dempster and a diagram of his apparatus for obtaining=
Fig. 19. Diagram of Anode in Dempster's latest apparatus.=
positive rays from metals. A full account is to appear in the
Physical Review. Fig. 19 shows the new arrangement of
vaporising furnace A and ionising filament C. The analysing
apparatus has already been described on p, 31 and the results wi=
th
.4F
5-9
f
'
1
k
Lithium.
\
1
\
1
\
)
J
[
<=3D/
v..
^^
/
K
9
30
ZO
10
60
6-1
6-9
Atomic Weight.
7-0
7-1
Fig. 20. Curve for Lithium.
146
APPENDIX III
147
magnesium on p. 81. Fig. 20 shows one of the curves obtained
with lithium. It will be seen that the relative intensities of t=
he
isotopes is entirely different from that found by the writer (p. =
86)
and also disagrees very definitely with the chemical atomic weight= . Dempster describes these relative intensities as varying very considerably. This is a most remarkable phenomenon and further information upon it is very desirable. There seems just a possibi= lity that the 6 line is enhanced by doubly charged carbon but it is =
not
easy to see where such particles could be produced.
l/oltS 943 928 913-5 899-5 886 873 860 847-5=
J
\
Zinc.
1
t
\
1
\
1
\
f
\
r
\
\
1
1
\
\i
1
1
\
/
\
I
/
1
=C2=AE
l/
\
1
i^
\
^^
62 63 64 65 66 67 Atomic Weight.
Fig. 21. Curve for Zinc.
68 69
70
Fig. 21 gives a remarkable curve obtained from zinc. This
indicates three strong isotopes and a faint fourth. The absolute=
scale of atomic weight is not known with certainty, and the valu= es 63, 65, 67, 69 are given by Dempster as those in best agreement=
with the atomic weight 65-37. Considering that the error in th= e
148 APPENDIX III
mean atomic weight of lithium, when calculated on these lines, is about 5 per cent, it would appear possible that these might = be a unit too high or too low. The probability of this is strengthene= d very much by the rule given on p. 110 connecting even atomic number with even atomic weight.
Results with calcium show only one line. This makes it extremely=
probable that this is a simple element of atomic weight 40 and=
therefore an isobare of argon. ^
Note. In a still later communication Dempster states that =
he
has been successful in using an anode of calcium to which a sma= U quantity of zinc had been added. By this means he is able to compare the masses of the zinc isotopes with the strong calcium=
maximum, assumed as 40. This gives the atomic weights as 64, 66, 68 and 70. The intensities are quite different to those in = the curve given above for zinc. 64 is now the strongest, 66 and 68=
fainter, while 70 is very faint indeed. No explanation is yet advanced for these remarkable irregularities in relative intensity.=
He has also observed a small maximum at 44 invariably accom-
panying the strong calcium maximum 40. This he considers to be
probably due to an isotope of that element present in smaU quant=
ity
as suggested by the atomic weight 40 07.
The above values are included provisionally in the tables on pages 89 and 142.
" V. p. 88.
INDEX
Abnormal hydrides, 98
Abundance of the elements, 111
Accuracy of mass-spectrograph, 60
Actinivim chain, 14, 15
Additive law of mass, 99
Alkali metals, mass-spectra of, 83
Alpha ray changes, 13
Analysis of the elements, 63
Andrade and Rutherford, 11
Anode, composite, 80, 86
hot, 80, 83, 84
Anticathode, silica, 48
Antimony, 78
Argon, 66
Aronbeeg, 123
,, and Harkins, 124
Atmolysis, separation by, 127
Atomic number, 13, 93
theory, 2
,, volume of isotopes, 18
weights, tables of, 89, 141
weights of radio -elements, 13,
141
Atoms, structure of, 90
Balke, Owens and Kremers, 142 Barkla, 93
Batuecas and Moles, 141 Baxter and Hodges, 142 and Parsons, 113 and Starkweather, 141 and Wilson, 142 Tani and Chapin, 142 Weatherell and Holmes, 73, 142 Beryllium, 88 Beta ray change, 13 Bohr, 94, 95, 121, 122, 123
,, atom, 95 BOLTWOOD, 1, 7 Boron, 72
anomalous atomic weight of,
114
trifluoride, 73
Bracketing, method of, 59, 69 Brauner and Krepelka, 141 Broek, Van den, 93, 94, 116 Bromine, 76
Bronsted and Hevesy, 135, 136, 139
Brosslera, 102, 104
Bruylants and Michielson, 142
Caesium, 87
,, anomalous atomic weight of, 114 Calcium, 88, 148 Calibration curve, 55 Camera of mass-spectrograph, 51
positive ray, 26
Canalstrahlen, 22 Carbon, 63
Carnotite, lead from, 124 Cathode rays, 22, 24 Chadwick, 94
and Rutherford, 103
Chapin, Baxter and Tani, 142 Chapman, 130
and DooTSON, 130
Chemical action, separation by, 133
law of radioactive change,
11 Chlorine, 65, 113
separation of the isotopes
of, 136 Classen, 31
and Wey, 142 Claude, 35 Cleveite, lead from, 17 Coincidence, method of, 57 Composite anode, 80, 86 Constancy of chemical atomic weights,
22 Cosmical effect of change of mass, 103 Crookes, 3, 4, 24, 115, 117 ,, dark space, 24, 35
theory of the evolution of
elements, 117 Curie, Mlle. I., 113
M., 18
Dalton's hypothesis, 2 Darwin, 15
Davies and Horton, 68 Deflection of positive rays, 27 Dempster, 31, 80, 81, 86, 114, 146
149
150
INDEX
Dempster's method of analysis, 31,146
Density balance, 35
,, of isotopic leads, 17, 18 Diffusion of neon, 39
separation by, 127 velocity, determination of, 20 Disintegration theory of the evolu- tion of elements, 116 Distillation of neon, 37 Distribution of lines on mass-
spectrum, 64 DooTSON and Chapman, 130 Du Bois magnet, 61
Eddington, 104
Einstein's theory of relativity, 103 Electrical theory of matter, 90 Electric discharge in gases, 23
,, field of mass-spectrograph, 50 Electricity as an element, 115 Electrochemical properties of isotopes,
10 Electron, the, 91
Element, meaning of the word, 115 Enskog, 130 Epstein, 95 ExNER and Haschek, 121
Fa JANS, 11
First order lines, 61
Fleck, 12
Fluorine, 72, 97
Focussing positive rays, 44
FOWLEB, 123
and Aston, 45
Fractional distillation, separation by,
133 Fbanck and Knipping, 68
Gehrcke, 102
,, and Reichenheim, 80, 83, 88 Geigek and Nuttall, 10, 13 Goldstein, 22 Gravitation effect on spectra, 121
separation by, 131
Groh and Hevesy, 20, 135
Hahn, 8
and Meitner, 8
Halation effect, 60 Half-tone plates, 25 Hall and Harkins, 116 Harkins, 102, 111, 116, 129
and Aronberg, 124
and Hall, 116
,, and Wilson, 116 Haschek and Exner, 121 Helium, 67, 69, 106
Hevesy, 10, 12, 19
and Bronsted, 136, 136,
139
and Groh, 20, 135
and Paneth, 11
and Zechmeisteb, 20
Hodges and Baxter, 142 Holmes, Baxteb and Weathebell,
73, 141 Honigschmid, 17, 18, 141, 142
and Horovitz, 18,
121 Horovitz and Honigschmid, 18, 121 HoBTON and Davies, 68 Hot anode, 80, 83, 84 Hydrochloric acid, diffusion of, 129 Hydrogen, 67, 69, 106 Hyman and Soddy, 17, 121
Ibbs, 130
Imes, 125, 126
Indicators, radioactive, 19
Infra-red spectrum of isotopes, 125
Intensity of positive rays, 44
Iodine, 78
Ionic dissociation theory, proof of, 20
lonisation in discharge tube, 24
Ionium, 1, 7, 9, 18
,, atomic weight of, 18 Isobares, 12, 13, 97, 110 Isotopes, definition of, 12
diagrams of, 97
discovery of, 5
melting point of, 18
refractive index of, 18
separation of, 127
solubility of, 18
table of, 89, 141
James and Stewabt, 142 JoLY and Poole, 133
Keetman, 7
Kernel of atom, 98
Kibchoff, 116
Knipping and Franck, 68
kohlweiler, 116
Kratzer, 126
Kremers, Owens and Balke, 142
Krepelka and Bbaun, 141
,, and RiCHABDS, 141
Krypton, 70
,, anomalous atomic weight of, 114
Landaueb and Wendt, 70 Langmuib, 95, 96, 99 Lead, atomic weight of, 16
,, from carnotite, 124
,, from thorite, 17
isotopes of, 14, 15
INDEX
15)
Lembert and Richards, 17, 121
Lewis-Langmuir atom, 95
LmDEMANN, 102, 124, 134, 139
,, and Aston, 131
Lines of first and second order, 61, 76
of reference, 55, 64
Lithium, 86, 97, 146 LooMis, 125, 126
LUDLAM, 129
McAxpiNE and Willard, 142
Magnesimn, 80
Magnetic field of mass-spectrograph,
51 Marckwald, 7, 8 Mass, change of, 100
deduced from parabolas, 28
deduced from mass -spectrum,
55 Mass-spectrograph, 43 Mass-spectrum, 47, 54 Measurement of lines on mass-
spectrum, 59 Meitner, 21
,, and Hahn, 8 Melting point of isotopes, 18 Mercury, 72, 80
parabolas of, 30
separation of the isotopes
of, 134 Merton, 121, 123, 124, 125 Mesothorium, 8, 10 Meta-elements, 4
Metallic elements, mass-spectra of, 80 Meteoric nickel, 113 MiCHiELSON and Bruylants, 142 Microbalance for density, 35 MiLLIKAN, 22, 91
Molecular lines of second order, 75 Moles and Batuecas, 141 MOSELEY, 11, 93, 115 Mtjller, 142 Multiply charged rays, 30
Natural numbers and atomic weights,
111 Negatively charged rays, 29, 62 Negative mass-spectra, 62, 66 Neon, 1, 33, 64, 97 Neuberger, 21 Nickel, 79
meteoric, 113
Nitrogen, 67, 110 Nomenclature of isotopes, 61 Nucleus atom, 10, 92, 97, 125
structure of, 101
Ntjttall and Geiger, 10, 13
Order, lines of first and second, 61 Owens, Balke and Kremers, 142 Oxygen, 63
Packing effect, 100
Paneth and Hevesy, 11
Parabola method of analysis, 25
Parsons and Baxter, 113
Perforated electrodes, 22, 24
Periodic law, 11, 12, 34
table of the elements, 144,
145 Period of radio-elements, 13 Perrin, 104 Phosphonas, 77
Photochemical separation, 137 Photographic plates for positive rays,
25 Planck's quantum, 95 Planetary electrons, 92 Poole, 133
and JoLY, 133
Positive ray paraljolas, 28
rays, 22
separation by, 136
Potassium, 87 Pressure diffusion, 131 Proton, the, 92 Protyle, 90, 118 Prout's hypothesis, 2, 90, 100
Radioactive isotopes, 7, 14
classification of,
21
transformations, 13, 14,
15 Radium B and lead, 11
D and lead, 11
Ramsay, 115
and Collie, 39
and Travers, 33
Ratner, 24 Rayleigh, 127 Reference lines, 55, 64 Refractive index of isotopes, 18 Reichenheim and Gehrcke, 80, 83,
88 Renz, 139
Resolving power of mass-spectro- graph, 60 Richards 17
and Krepelka, 141
and Lembert, 17, 121
and Wads WORTH, 17
Richardson, 85 Rossi and Russell, 9, 120 Rubidium, 87 Russell, U
and Rossi, 9, 120
Rutherford, Sir E., 7, 9, 13, 92, 93, 102
and Chadwick, 103
and Andrade, 11
Rydberg, 141
162
INDEX
SCHUTZENBERGER, 3
Screens, willemite, 25
Secondary rays, 29
Second order, lines of the, 61
Selenium, 77
Separation of isotopes, 127
Silicon, 72
fluoride, 74
Skaupy, 139
Slit system of mass-spectrograph, 49 Smith and Van Haagen, 72 SoDDY, 6, 8, 10, 11, 12, 13, 14, 16, 17, 35
and Hyman, 17, 121
Sodium, 86 Solubility of isotopes, 18
SOMMERFEIiD, 95
Spectra of isotopes, 9, 121,
Spectrum lines, form of, 53
Spencer, 91
Starkweather and Baxter, 141
Stas, 91
Statistical relation of isotopes, 109
Stewart, 11, 12
and James, 142
Sulphur, 76
Tani, Baxter and Chapin, 142 Tellurium, 77 Thermal diffusion, 129 Third order line of argon, 67
lines of, 61
Thomson, G. P., 86, 88
Sir J. J., 1, 22, 29, 33, 62, 70, 72, 75, 84, 91, 129 Thorite, 17, 18 Thorium, 7, 9, 14, 15, 18, 120
Thorium, chain, 17, 18, 116
,, atomic weight of, 18
Tin, 78 Travers, 39
and Ramsay, 33
Triatomic hydrogen, 70
Unitary theory of matter, 90 Uranium, 10, 120 ,, chain, 15
Valency electrons, 98
Van Haagen and Smith, 72
Wadsworth and Richards, 17 Watson, 33
and Aston, 24, 35
Weatherell, Baxter and Holmes,
73, 141 Welsbach, 8
Wendt and Landaueb, 70 Wey and Classen, 142 Whole number rule, 90 WiEN, 22
WiLLARD and McAlpine, 142 Willemite screens, 25 Wilson and Baxter, 142
and Harkins, 116
Xenon, 70
- anomalous atomic weight of, 114
X-ray spectra of isotopes, 1 1
Zechmeister and Hevesy, 20 Zinc, 147
