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The effect of X-rays upon thermoluminescence
CURRENT
814
TOPICS.
[J. F. I.
Effect of X-rays upon Thermoluminescence. FRANCES (J. Opt. Sot. Am., Jan., I927.)-Fluorite and other materials exhibit the phenomenon of thermoluminescence, that is, they emit light when heated to a moderate temperature. Miss Wick has found that this effect is modified by subjecting the source of light to a preliminary treatment with X-rays. A specimen of fluorite from Franklin County, N. J., when heated emitted strong green light. When this specimen was subjected to X-rays and then heated there appeared first a yellow luminescence lasting a short time and then the green light. The intensity of the thermoluminescent light, in all cases orange in color, emitted by calcite was increased by letting X-rays fall upon the mineral. By such treatment one piece of calcite was caused to display a green luminescence before the orange appeared. G. F. S. The
G. WICK.
Cell as a Calorimeter.-STANLEY P. REIMANN, Hospital, Philadelphia (Proc. Sot. Exp. Biology and Medicine, 1926, 23, 52o-523), uses a photo-electric cell as a calorimeter. Light from a source of illumination is passed through a calorimeter cup containing the colored solution, and the transmitted light is caused to fall upon a photo-electric cell. The current generated in the cell is then measured. The standard solution and the unknown solution may be matched by changing the height of the column of liquid in the calorimeter cup until the two solutions give the same current; or the distance of the source of light from the photo-eledric cell may be varied so as to obtain the same current with both solutions, keeping the height of the liquid in the cup The concentration of the solute in the unknown is then constant. calculated. J. S. H. Photo-electric of the Lankenau
V. SHANNON (Proc. U. S. 21, 1-15) has investigated the oxidation of meteoric iron and reached the following conclusions. Magnetite is formed only in relatively small amounts as a transitory The magnetite and the iron and unstable stage in the oxidation. itself are rapidly converted into limonite or ferric hydroxide without the intermediate formation of ferromagnetic ferric oxide in appreciable amounts. However, meteoric iron contains nickel, cobalt, and During the oxidation, persistent ferrites of these metals, copper. They e.g., trevorite or nickelous ferrite NiO.Fe,O,, are formed. are strongly ferromagnetic, and their presence accounts for the magNo evidence exists of the netic properties of the resulting mass. formation of any ferromagnetic oxide other than the ferrites of the The sole function of chlorides in these changes bivalent metals. apparently is to promote the formation of the amorphous ferric hydroxide from the metal. Terrestrial occurrences of ferromagnetic ferric oxide have a different composition and origin, and present no J. S. H. analogies to the oxidation of meteorites. Oxidation
of Meteoric
Iron.-EARL
_vational Museuwz, 1927, 72, Article
814
TOPICS.
[J. F. I.
Effect of X-rays upon Thermoluminescence. FRANCES (J. Opt. Sot. Am., Jan., I927.)-Fluorite and other materials exhibit the phenomenon of thermoluminescence, that is, they emit light when heated to a moderate temperature. Miss Wick has found that this effect is modified by subjecting the source of light to a preliminary treatment with X-rays. A specimen of fluorite from Franklin County, N. J., when heated emitted strong green light. When this specimen was subjected to X-rays and then heated there appeared first a yellow luminescence lasting a short time and then the green light. The intensity of the thermoluminescent light, in all cases orange in color, emitted by calcite was increased by letting X-rays fall upon the mineral. By such treatment one piece of calcite was caused to display a green luminescence before the orange appeared. G. F. S. The
G. WICK.
Cell as a Calorimeter.-STANLEY P. REIMANN, Hospital, Philadelphia (Proc. Sot. Exp. Biology and Medicine, 1926, 23, 52o-523), uses a photo-electric cell as a calorimeter. Light from a source of illumination is passed through a calorimeter cup containing the colored solution, and the transmitted light is caused to fall upon a photo-electric cell. The current generated in the cell is then measured. The standard solution and the unknown solution may be matched by changing the height of the column of liquid in the calorimeter cup until the two solutions give the same current; or the distance of the source of light from the photo-eledric cell may be varied so as to obtain the same current with both solutions, keeping the height of the liquid in the cup The concentration of the solute in the unknown is then constant. calculated. J. S. H. Photo-electric of the Lankenau
V. SHANNON (Proc. U. S. 21, 1-15) has investigated the oxidation of meteoric iron and reached the following conclusions. Magnetite is formed only in relatively small amounts as a transitory The magnetite and the iron and unstable stage in the oxidation. itself are rapidly converted into limonite or ferric hydroxide without the intermediate formation of ferromagnetic ferric oxide in appreciable amounts. However, meteoric iron contains nickel, cobalt, and During the oxidation, persistent ferrites of these metals, copper. They e.g., trevorite or nickelous ferrite NiO.Fe,O,, are formed. are strongly ferromagnetic, and their presence accounts for the magNo evidence exists of the netic properties of the resulting mass. formation of any ferromagnetic oxide other than the ferrites of the The sole function of chlorides in these changes bivalent metals. apparently is to promote the formation of the amorphous ferric hydroxide from the metal. Terrestrial occurrences of ferromagnetic ferric oxide have a different composition and origin, and present no J. S. H. analogies to the oxidation of meteorites. Oxidation
of Meteoric
Iron.-EARL
_vational Museuwz, 1927, 72, Article