109 



Effect of Radium on Electrolytic Conductivity. 



By Ryland Ratliff. 



The material used was one-tentb of a gram of "Curie" radiimi 

 chloride of 10,000 strength phnced at the disposal of the writer through 

 the kindness of Dr. Foley and the other Indiana University authorities. 



A number of the usual experiments were tirst performed to test the 

 quality of the material. These included photographing the fluorescent 

 action of the radium upon small diamonds and Wilhemite. In these 

 and kindred experiments good results were obtained. 



Two attempts were made to obtain a photograph of the spectrum by 

 means of the Rowland concave and Bra shear mounting. In the first 

 exposure of 90 hours the radium chloride was placed directly in front of 

 the slit which Avas made unusually wide (probably too wide). A second 

 exposure of 1G2 hoiu's was made by placing the radium .slightly to one 

 side of the slit and the fluorescing Wilhemite directly in front of it. In 

 this trial the slit was made narrower but was considerably wider than in 

 ordinary spectrum work. Neither exposure yielded any effect other than 

 a slight fogging of the plate. The remainder of the work was devoted 

 to the problem, as above stated, of determining the effect upon elec- 

 trolytic conductivity. 



The apparatus employed is represented diagrammatically in Fig. 1. 



Glass tubes I and II filled with the electrolytic solution are intro- 

 duced into the two arms of the AVheatstone bridge BD and CD. The 

 copper disks di and d., are placed as nearly as possible the same distance 

 apart as dj and d^. Then when resistances R and Ki are made the same 

 the bridge Avill of course be balanced approximately. R and Rj were 

 usually made of from 800 to 1,200 ohms each. With the bridge balanced 

 the radium is placed as near as practicable to I or II and the direction 

 and amount of deflection in each case is noted. 



Theoretically the back E. M. F. should be the same in each tube, 

 but it was found to be impossible to get it so in practice for any con- 

 siderable time. Hence the greatest difficulty in the way of definite posi- 

 tive conclusive results is due to the drift of the needle. A Rowland D'Ar- 

 sonval galvanometer with a sensitiveness of one megohm was em- 

 ployed in the major part of the work. 



