Radium fluorescence

Other uses are to produce phosphorescence and fluorescence in organic compounds and for scintillation screens on instruments used to detect radiation. Radium salts were used in the past to paint the dials of luminous clock faces that glow in the dark. 

Perrin R, Mouvement Brownien d un ellipsoide. II. Rotation libre et depolarisation des fluorescences. Translation et diffusion de molecule ellipsoidales, J. Phys. Radium, 7, 1, 1936. 

According to Ebler (Ref 5) Ba azide is not decompd by exposure to radium. Gyunter et al (Ref 15) also found that, unlike other azides, Ba azide is not decompd by X-rays of radium. X-rays of less than 0.7 A° also have no effect while soft X-rays produce a weak blue fluorescence. By using a Hadding tube,... 

Fluorescence.—The majority of platinocyanides fluoresce under the stimulus of ultra-violet light1 or of radium radiations, although some salts show no sign of this property. Magnesium, erbium, yttrium, thallium and uranyl salts are cases in point. 

It is certainly very remarkable that uranyl platinocyanide should fail to respond to the stimulus of ultra-violet light or to radium radiations. Both the uranyl and the platinocyanide groups can confer the property of fluorescence upon salts containing them, yet when they both occur in the same complex, there is no sign of fluorescence. 

By electrolysis of a solution of barium cyanide between platinum electrodes, using an alternating current, a solution of barium platino-cyanide has been obtained 1 which, upon concentration, crystallised out in yellow, slightly dichroic crystals, exhibiting a slight fluorescence under radium. 

Barium platinocyanide, after prolonged exposure to radiation from radium compounds, becomes brown or red and loses its fluorescent properties. The only way to completely restqje the red crystals to their fluorescent state is by solution and recrystallisation,1 although gentle heating will partially restore them. This is well illustrated by the following table ... 

Radium Barium Platinocyanide.—-Since the majority of platino-cyanides fluoresce under the influence of radiations from radioactive substances, the radium salt should be self-luminous. The radium barium salt was prepared1 by dissolving radioactive barium chloride in water and boiling the solution with excess of silver platinocyanide. After filtering off insoluble silver salts the solution was allowed to crystallise in a desiccator. 

The crystals deposited last were reddish in colour, and brightly luminous at first, but the intensity of their luminosity gradually diminished, and the reddish tint deepened in colour. No doubt this is attributable to alteration of the barium platinocyanide in the complex, since the free salt upon exposure to radium radiations undergoes some change, resulting in a weakening of the fluorescence as has already been pointed out (see p. 321). 

The radium barium salt recovers its fluorescent properties upon recrystallisation, and the effect is enhanced by contact with its own saturated aqueous solution, probably because the water prevents the alteration referred to. 

Cyanogen derivatives arc numerous and capable of great complexity. Platinous cyanide Pt(CN)3, is obtained as a yellow precipitate when mercuric cyanide is added to a solution of alkali chlorplatinite. Double cyanides of the general formula M 2Pt(CN)4 are formed by such reactions as 6 KCN + PtCL = K2Pt(CN) + 4 KC1 + (CN),. These platino-cyanides do not respond to the ordinary tests for platinum. These compounds yield beautifully colored hydrates, and the barium and calcium hydrates have optical isomeric modifications.2 Certain of these hydrates become remarkably fluorescent under excitation from ultraviolet light or radium. 

Write a balanced nuclear equation for the reaction in which oxygen-15 undergoes positron emission. 7. Thorium-229 is used to increase the lifetime of fluorescent bulbs. What type of decay occurs when thorium-229 decays to form radium-225 8. Challenge The figure at right shows one way that bismuth-212 can decay, producing isotopes A and B. a. Write a balanced nuclear equation for this decay. b. Identify the isotopes A and B that are produced. V Beta particle Bismuth-212 Alpha particle J... 

Jean-Baptiste Perrin (1870-1942). .. was a French physicist who worked on various subjects, for instance, on cathode rays, fluorescence, sound propagation, and the decay of radium. A major part of his scientiflc life was dedicated to colloids. His investigations on the Brownian motion of colloids by means of the previously developed ultramicroscope verified Einstein s statistic explanation of this phenomenon and thereby confirmed the atomic nature of matter. Moreover, Perrin was able to closely limit the possible range of Avogadro s number and he discovered the sedimentation-diffusion equilibrium. For his work on the discontinuous structure of matter and especially for his discovery of sedimentation equilibrium he received 1926 the Nobel Prize in Physics. 

Perrin, F., Brownian movement of an ellipsoid. 11. Free rotation and depolarization of fluorescence. Translation and diffusion of ellipsoidal molecules, /. Phys. Radium, 7,1,1936. 

The isotope Pm is commercially available and has found some use. Its emission of low-energy 3-particles is used industrially to measure the thickness of strip steel and paper. To some extent it is also used in miniature batteries with a useful hfe of about five years. These have been tested for such diverse purposes as pacemakers and guided missiles. A paint containing Pm and a material that fluoresces with a bluish-green color after being hit by the P-particles may be used for hour hands and dials in watches. Promethium has replaced radium for reasons of health. 

X-rays fascinated the scientific community and the general public alike. Scientists investigated further and soon found related phenomena. Chief among these was a discovery made by Antoine-Henri Becquerel, a professor of physics in Paris. While studying the characteristics of fluorescent materials in March 1896, he discovered that uranium exposed a photographic plate when placed next to it. He had found another form of radiation, one that was emitted spontaneously from a natural substance. To investigate further, Becquerel collaborated with a husband-and-wife scientific team, Pierre Curie and Maria Sklodowska-Curie. Sklodowska-Curie devised an electrometer that could measure this radioactivity, as she called it, and studied a number of materials. In 1898 the trio managed to separate from uranium ore two radioactive elements polonium and radium. 

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