CHAPTER VI 



RADIUM PREPARATIONS AND METHODS OF EXPOSURE 



The radium preparations used in physical and ph3'siological 

 experiments are sahs of that element. The one most commonly em- 

 ployed is radium bromide, though the more expensive chloride is 

 sometimes used. The salt may be obtained in at least three different 

 kinds of containers, (i) Thin glass tubes, usually about 30 mm. 

 long, and, in the newer preparations, protected by being placed in 

 metallic holders with openings extending nearly the length of the 

 tube. (2) Aluminium tubes, devised by Mr. Hugo Lieber. (3) Hard 

 rubber cells with brass caps having a mica window. By all of the 

 above containers the o. rays are practically cut off, as they cannot 

 penetrate the walls. 



In addition to these preparations, a radium coating has been 

 invented by Lieber, ^"^ by the use of which, not only the a rays, but 

 also the radium emanation becomes available for experimentation. 

 The process of preparing this coating is thus described by Lieber : 



"Radium coatings are made in the following manner: Radium 

 is dissolved in a suitable solvent and into this solution a suitable ma- 

 terial is dipped. This material is then withdrawn, with radium solu- 

 tion adhering to it. The solvent quickly evaporates, leaving the ma- 

 terial covered with an exceedingly thin film of radium. The kind 

 of solvent to be used is determined by the nature of the material to 

 be coated. Such solvents are employed as have a tendency to soften 

 the material which is to be coated. Thus, if celluloid rods, discs, or 

 similar instruments are to receive a radium coating, in order to be 

 used for therapeutic purposes, solvents such as alcohol, amyl acetate, 

 etc., may be employed. These solvents have a tendency to soften 

 the celluloid temporarily. When the solvent evaporates, the radium 

 has been uniformly distributed over the celluloid, and has also been 

 incorporated in its surface. In order to prevent accidental removal 

 of the radium in such coatings, the celluloid instruments produced in 

 this way are dipped for a short time in a collodion solution. By this 

 process the whole radium coating is covered by a very thin film of 

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