In a search for radio-activity in different minerals, M. and Mme Curie found a greater effect in pitch-blende than its contents of uranium warranted, and, led by the radio-active property alone, they succeeded, by a long series of chemical separations, in isolating compounds of a new and intensely radio-active substance which they named radium.英文原著 · 《Darwin and Modern Science》
The transmutation theory of radio-activity was formulated by Rutherford (Rutherford, "Radio-activity" (2nd edition), Cambridge, 1905, page 307.) and Soddy in 1903. By its light, all recent work on the subject has been guided; it has stood the supreme test of a hypothesis, and shown power to suggest new investigations and to co-ordinate and explain them, when carried out. We have summarised the evidence which led to the conception of the theory; we have now to consider the progress which has been made in tracing the successive disintegration of radio-active atoms.英文原著 · 《Darwin and Modern Science》
It is a remarkable fact that the intensity of the radiation from a radio- active body is independent of the external conditions of temperature, pressure, etc. which modify so profoundly almost all other physical and chemical processes. Exposure to the extreme cold of liquid air, or to the great heat of a furnace, leaves the radio-activity of a substance unchanged, apparent exceptions to this statement having been traced to secondary causes.英文原著 · 《Darwin and Modern Science》
We shall return to this point, and trace farther the history of the radio- active matter. At present we wish to emphasise the fact that, as in other cases, the radio-activity of the emanation is accompanied by the appearance of a new kind of substance with distinct chemical properties.英文原著 · 《Darwin and Modern Science》
But the most thorough investigation of a radio-active pedigree is found in Rutherford's classical researches on the successive disintegration products of radium, in order to follow the evidence on which his results are founded, we must describe more fully the process of decay of the activity of a simple radio-active substance. The decay of activity of the body known as uranium-X is shown in a falling curve (Fig. It will be seen that, in each successive 22 days, the activity falls to half the value it possessed at the beginning.英文原著 · 《Darwin and Modern Science》
One such product has been indicated above. The alpha-ray particles appear to possess the mass of helium atoms, and the growth of helium has been detected by its spectrum in a tube of radium emanation. Moreover, helium is found occluded in most if not all radio-active minerals in amount which approaches, but never exceeds, the quantity suggested by theory. We may safely regard such helium as formed by the accumulation of alpha-ray particles given out by successive radio-active changes.英文原著 · 《Darwin and Modern Science》
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We'll be long gone by the time they realize it's half cake-half styrofoam from the Radio Shack garbage.美剧 · 《2 Broke Girls》