The Atomic Weight of the Radium Emanation

Text from page 1: In the disintegration of the radioactive elements, since each a-transformation involves the loss of an atom of helium and nothing else which in weighable, the atomic weight of the product should be just 3.99 less than that of the origianl substance, since 3.99 is the atomic weight of the helium evolved during the a-transformation. Thus if radium has an atomic weight of 225.97, radium emanation, the result of the loss of one a-particle, should have an atomic weight of 221.98; radium D, involving the loss of three more a-particles, should be 210.01; and radium G, yet another a-transformation, hsould be 206.02.

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Atomic Weight of Radium Emanation

Journal of the Röntgen Society ◽

10.1259/jrs.1910.0028 ◽

1910 ◽

Vol 6 (23) ◽

pp. 56-56

Author(s):

F. Soddy

Keyword(s):

Atomic Weight ◽

Radium Emanation

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THE ATOMIC WEIGHT OF RADIUM EMANATION (NITON)

Science ◽

10.1126/science.43.1109.464 ◽

1916 ◽

Vol 43 (1109) ◽

pp. 464-465 ◽

Cited By ~ 2

Author(s):

S. C. Lind

Keyword(s):

Atomic Weight ◽

Radium Emanation

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The density of niton (“radium emanation”) and the disintegration theory

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1911.0006 ◽

1911 ◽

Vol 84 (573) ◽

pp. 536-550 ◽

Cited By ~ 14

Keyword(s):

Solid State ◽

Helium Atom ◽

Critical Velocity ◽

Electric Charge ◽

Small Volume ◽

Direct Evidence ◽

Atomic Weight ◽

The Other ◽

Radium Emanation ◽

Successive Change

According to the disintegration theory of radioactive change, a definite number of atoms of radium break up per second, each evolving an α -particle which ultimately becomes a helium atom, leaving behind lighter molecules which form the gas known as “radium emanation,” or niton. The identity of the α -particle after it has lost its electric charge with the helium atom has been convincingly proved by Rutherford and Geiger; and measurements of the volume of helium evolved from niton by Ramsay and Soddy, and from radium in equilibrium with its disintegration-products by Dewar, render it exceedingly probable that in each successive change from radium to radium D only one α -particle is expelled per atom. If, then, the view is held that the radium atom on disintegration to niton splits up into two parts only, one of which is the α -particle, then the atomic weight of the resulting niton is 226·4—4 = 222·4. On the other hand, it may be supposed that the disintegrating radium atom splits up into three or more parts; helium, and two other bodies of higher atomic weight, if three parts. On account of its greater mass, the heavier particle might be expelled below the critical velocity necessary for the formation of ions in the air, and might itself be non-radioactive; if this were the case, its presence in a solid state would almost certainly escape detection. There is no direct evidence against such a supposition, for the atomic weights of none of the products of the disintegration of radium have been determined. Experiment alone can settle this question of the true atomic weight of niton; but on account of the exceedingly small volume of this gas obtainable from a relatively large weight of radium, the experiment is by no means easy.

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Elemental Analysis of Phloem Tissue in Lemna Minor Root Tips

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600003470 ◽

1980 ◽

Vol 38 ◽

pp. 798-799

Author(s):

Patrick Echlin ◽

Thomas Hayes ◽

Clifford Lai ◽

Greg Hook

Keyword(s):

Vascular Tissue ◽

Lemna Minor ◽

Atomic Weight ◽

Companion Cell ◽

Root Tips ◽

Phloem Tissue ◽

Cell Stage ◽

Phloem Parenchyma ◽

Parenchyma Cells ◽

Xylem Element

Studies (1—4) have shown that it is possible to distinguish different stages of phloem tissue differentiation in the developing roots of Lemna minor by examination in the transmission, scanning, and optical microscopes. A disorganized meristem, immediately behind the root-cap, gives rise to the vascular tissue, which consists of single central xylem element surrounded by a ring of phloem parenchyma cells. This ring of cells is first seen at the 4-5 cell stage, but increases to as many as 11 cells by repeated radial anticlinal divisions. At some point, usually at or shortly after the 8 cell stage, two phloem parenchyma cells located opposite each other on the ring of cells, undergo an unsynchronized, periclinal division to give rise to the sieve element and companion cell. Because of the limited number of cells involved, this developmental sequence offers a relatively simple system in which some of the factors underlying cell division and differentiation may be investigated, including the distribution of diffusible low atomic weight elements within individual cells of the phloem tissue.

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