521 



Tables 630-632 



TABLE 630. — Miscellaneous Radioactivity Constants 



(Recommended by International Radium Standards Commission, 1930, 

 Rev. Mod. Phys., 1931.) 



vioc 2 = 5-9303 X io" 3 , a particles. m n , a particle = 6.598 X io" 24 g. 



moC 2 /2c = 6.2162 X io 6 , a particles. 



j;r c 2 = 8.1207 X io -7 , j8 particles. m , electron = 9.040 X io -2S g. 



for e/vin — 5.2763 X io 17 e.s.u./g. for /3 particle. 

 vioC 2 /e = 1.7034 X io 3 , for ditto. 



Kinetic energy = E = m<,C 2 (r) — 1 ) = 5.9303 X io~ 3 (77 — 1 ) erg. for a particles 



/3 = velocity particle/velocity light; t? = (1— /3 2 )~£, m = tnoV- 

 E = 8.1252 X io~ 7 (t? — 1) erg, /3 particles. 

 E= 5.9303 X io" 3 (t; — 1) erg, a particles. 



Velocity in equivalent volts, p = 299.8o£/2e = 3.1426 X io"£, a particles. 



— 2gg.8oE/c = 6.2851 X io n £, /3 particles. 



Product of magnetic field strength X radius of curvature of the path : 



log R = (m c 2 /2c)r)P = 6.2162 X io 6 77/3, a particles. 

 = (m c 2 /e )7?j8= 1.7034 X io 3 t)/3, j8 particles. 

 X = he IE — 1.9628 X io w /£ for h = 6.547 X io" 27 erg.sec. 

 1.9637 X io 16 /E for h = 6.S5 X io" 27 erg.sec. 

 Z== no. a particles emitted per sec. from one g Radium = 3.7 X io 10 . 



(The chief source of error lies in the Ra equivalent of the preparation (e.g., RaC). This 

 arises from the decay-curve of RaB-RaC. Moreover in washing with alcohol to remove 

 residual radon, RaB is dissolved in excess of RaC. The error causes a minimal value of Z.) 



Ratio Ra/U in old unaltered minerals =3.4 X io" 7 ; U/Ra = 2.94 X io 6 . 



Basic values for calculation of number of ion pairs produced by one a particle : 



k =z koRj and velocity from v 3 = aoRo (all data o° C, 760 mm). 

 As basis for ko = Zk = 8.18 X io 15 (Meyer-Schweidler, 1927) 



and Z = 3.7X10" 



For RaC /?o=6.58cm 



k = 8.18 X io 16 /37 X io 10 = k X 6.58!, £ = 6.296 X io 4 . 

 Recommended value: £0 = 6.3 X io 4 . 



For Go, different values are obtained according to the choice of RaC, ThC or Po as 

 reference. This may mean that v 3 = aR is not exact and that the definition of the range 

 as the intercept of the descending line of the Bragg curve with the abscissa has no 

 theoretical basis. 



TABLE 631. — Relative Phosphorescence Excited by Radium 

 (Becquerel, C. R. 129, 912, 1899.) 



Without screen, Hexagonal zinc blende . 



" Pt. cyanide of barium . 



" Diamond 



" Double sulphate Ur and K 



" " Calcium fluoride . . 



The screen of black paper absorbed most of the a rays to which the phosphorescence was greatly due. For the last 

 column the intensity without screen was taken as unity. The y rays have very little effect. 



TABLE 632. — Vapor Pressure of the Radium Emanation in cm of Mercury 



(Rutherford and Ramsay, Philos. Mag. 17, 723, 1909, Gray and Ramsay, Trans. 



Chem. Soc. 95, 1073, 1909.) 



Temperature C° — 127 — 101 — 65 — 56 — io° -f-17 +49° +73° +100 +104 (crit.) 



Vapor Pressure 

 Smithsonian Tables 



0.9 



76 100 500 1000 2000 3000 4500 4745 



