IX, A, 1 



Wright and Smith: Radium Emanation 



73 



exposures of forty hours. The tubular electric furnace, used 

 in our former determinations, was replaced by an air-blast 

 charcoal furnace which enabled us to heat the charcoal tubes 

 to a bright red heat or, as near as the eye could tell, to the 

 same temperature as formerly used. During all our work the 

 charcoal tubes have always been heated until practically all 

 the gas possible was driven off. The volume of gas given off 

 by a definite weight of charcoal for any given distribution seems 

 to be practically constant. 



Since it was desirable that the results of observations on 

 Mount Pauai should be directly comparable with those taken in 

 Manila, the method of taking observations previously described 

 was rigidly adhered to throughout the entire series of deter- 

 minations, the results of which are given in Table IX. The 

 rate of flow of air through each set of charcoal tubes was kept 

 constant for all the exposures at 0.5 liter per minute. The 

 same portion of the standard solution, containing 6.28x10"^*' 

 gram of radium, was used throughout the entire series. 



Table IX. — Radiutn-emanation content of the atmosphere of Mount Pauai. 



Date. 



Apr. 



23 



Apr. 



25 



Apr. 



28 



May 



1 



May 



3 



May 



4 



May 



6 



May 



7 



May 



8 



1913. 



Duration 

 of expo- 

 sure. 



ElectroBcope reading 



in divisions per 



minute due to emanation 



from — 



Given vol- 

 itune of air. 



May 10. 



Mean . 



Hours. 

 20 

 20 

 20 

 20 

 20 

 40 

 10 

 10 

 20 

 20 



Given vol- 

 ume of air 

 and stand- 

 ard solu- 

 tion. 



Electroscope reading 



due to emanation 



from — 



Solution 

 alone. 



I 



0.042 

 0.044 

 0.087 

 0.070 

 0.087 

 0.045 

 0.035 

 0.051 

 0.028 

 0.073 



0.455 

 0.313 

 0.462 

 0.444 

 0.407 

 0.522 

 0.354 

 0.354 

 0.475 

 0.563 



0.413 

 0.269 

 0.375 

 0.374 

 0.320 

 0.477 

 0.319 

 0.319 

 0.447 

 0.493 



I 



Solution 

 for an ex- 

 posure of 20 

 hours times 

 decay f ae 

 tor. 



0.480 

 0.311 

 0.455 

 0.434 

 0.372 

 0.321 

 0.686 

 0.686 

 0.518 

 a 0.572 



Emanation 



per cubic 



meter 



of air 



expressed 



in its 



radium 



equivalent. 



Grams X 



1012. 



15.97 

 25.68 

 36.42 

 29.39 

 42.68 

 14.81 

 17.22 

 24.96 

 9.83 

 24.34 



24.13 



» The last observation was taken with 2 tubes in series on the solution side, although only 

 the first tube is taken into consideration in the calculation. The presence of the second tube 

 may have had an influence on the absorption in the first tube, by changing the air current 

 streams. 



Expressed in terms of the radium equivalent, the mean value 

 of the 10 determinations of the radium emanation per cubic 



