Aston 1922/Contents
CONTENTS
CHAPTER I Introduction
1. Introduction .....
2. Hypothesis of Dalton and Prout
3. Crookes' Meta-elements .
4. The discovery of Isotopes
PAGE
1 2 4, 6
CHAPTER II
The Radioactive Isotopes
5. Chemical identities among the radioactive elements
6. Spectroscopic identity of isotopes .
7. The chemical law of Radioactive change
8. Isobares ......
9. The Radioactive Transformations .
10. The Atomic weight of Lead .
11. Atomic weights of Thorium and Ionium
12. Use of radioactive isotopes as indicators
13. Classification of the radioactive isotopes .
7
9
11
12
13
16
18
19
21
CHAPTER III
Positive Rays
14. Nature of Positive Rays ...... 22
15. Mechanism of the electric discharge in gases at low pressure =
. 23
16. The Crookes Dark Space 24
17. Methods of detecting positive rays ..... 25
18. Sir J. J. Thomson's " Parabola " method of analysis . =
25
19. Secondary rays ........ 29
20. Negatively charged rays ...... 29
21. Rays with multiple charges ...... 30
22. Dempster's method of positive ray analysis ... 31
CHAPTER IV
Neon
23. Positive ray analysis of neon .
24. Apparatus for the determination of density
25. Method of using the density balance
26. Experiments on separation by distillation
27. Experiments on separation by diffusion .
28. Second attempt at separation by diffusion
29. The analysis of neon by the Mass-spectrograph
33
35 36 37 39 41 41
VI
CONTENTS
PAGE
CHAPTER V
The Mass-Spectbograph
30. Limitations of the parabola method
31. Methods of increasing the intensity of the spot
32. Possibilities of " focussing " .
33. Principle of the Mass-spectrograph
34. Optical analogue .
35. The discharge tube
36. The slit system
37. The electric field
38. The magnetic field
39. The camera .
40. Experimental procedure
41. Form of the Spectrum Lines
42. The distribution of the mass
graphic plate .
43. Practical method of deducing the effective mass of a parti
from the position of its line on the photograph
44. Comparison of masses by the method of coincidence
45. The measurement of the lines ....
46. Resolving power and acciiracy of mass determination
47. Order of results and nomenclature
48. Lines of the first, second and higher orders .
49. Negative mass-spectra ......
-spectrum over the photo
cle
CHAPTER VI
Analysis of the Elements
50. Arrangement of results ....
51. Oxygen and carbon ....
52. Neon
53. Possibility of a third isotope of neon 64. Chlorine ......
55. Argon .......
56. Nitrogen ......
57. Hydrogen and helium ....
58. The determination of the masses of atoms of hydrogen and
heliiim by the method of " Bracketing "
59. Triatomic hydrogen
60. Krypton and Xenon
61. Mercury
62. Boron, Fluorine, Silicon
63. Molecular lines of the second order
64. Bromine
65. Svdphur
66. Phosphorus. Arsenic
67. Selenium. Tellurium
68. Iodine .
69. Antimony
70. Tin .
71. Nickel .
CONTENTS
vu
CHAPTER VII
Analysis of the Elements (Continued)
72. Positive rays of metallic elements
73. Dempster's analysis of Magnesium
74. The Mass-spectra of the alkali metals
75. Experiments with the parabola method of analysis
76. Lithium
77. Sodium
78. Potassium
79. Rubidium
80. Caesium
81. Thomson's work on Beryllium
82. Calciiom and Strontitmi .
83. Table of Elements and Isotopes
PAGE
80 80 83 84 86 86 87 87 87 88 88 88
CHAPTER VIII
The Electbical Theory or Matter
84. The whole number rule ......
85. The unitary theory of the constitution of matter .
86. The atom of negative electricity, or electron .
87. The atom of positive electricity, or proton
88. The nucleus atom .......
89. Moseley's atomic numbers .....
90. The Bolir atom
91. The Lewis Langmuir atom .....
92. Diagrammatical representation of atoms of Isotopes and
Isobares .......
93. The relation between Isotopes and Elements in the same
Group ........
94. Abnormal compounds formed by charged atoms
95. The failure of the additive law in respect to mass
96. The explanation of the fractional mass of the hydrogen
atom by the hypothesis of "packing"
97. The structure of the nucleus .....
98. Cosmical effects due to change of mass .
99. The stable systems of protons and electrons known to=
occur .........
90
90
91
92
92
93
95
95
96
98 98 99
100 101 103
105
CHAPTER IX
Isotopes and Atomic Numbers
100. The relation between chemical atomic weight and atomic
number ......... 108
101. Statistical relations exhibited by elements and their isotopes=
. 109
102. The preponderance of elements of even atomic number . Il= l
103. The constancy of chemical atomic weights . . .112
104. The agreement between the chemical atomic weight and
the mean atomic weight deduced from the mass- spectrum . . . . . . . .113
105. The meaning of the word "element" . . . .115
106. Disintegration theory of the evolution of the elements .
116
107. Crookes' theory of the evolution of the elements . .117
viii CONTENTS
PAGE
CHAPTER X
The Spectra or Isotopes
108. The spectra of isotopes . . . . . . .121
109. The magnitude of the gravitational effect . . .121
110. Deviation of the Bolir orbits due to change in the position=
of
the centre of gravity of the rotating system . . 122
111. Later experiments of Aronberg and Merton . . .123
112. " Isotope " effect on the infra-red spectrum of molecules = . 126
CHAPTER XI
The Separation of Isotopes
113. The separation of isotopes .....
114. Separation by diffusion .....
115. The separation of the isotopes of chlorine by the difiusion=
of HCI
116. Separation by thermal diffusion ....
117. Separation by gravitation or "pressure diffusion" .
118. Separation by chemical action or ordinary fraction= al
distillation .......
119. Separation by evaporation at very low pressure
120. Separation of the isotopes of chlorine by free evaporation
121. Separation by positive rays .....
122. Separation by photochemical methods
123. Other methods of separation and general conclusions
127
127
129 129 131
133 134 136 136 137 138
Appendix I. Table of Atomic Weights and Isotopes of
THE Elements . . . . .141
II. The Periodic Table of the Elements . 14=
4
III. Recent Results obtained by Dempster . = 146
LIST OF PLATES
Plate I. Positive Ray Parabolas . . . T= o face page 28
- II. Original Mass-Spectrograph . . .=
,,46
- III. Mass Spectra . . . =
. 66
- IV. Mass Spectra 72
