76 ■ '^^^ Philippine Journal of Science 1914 



SUMMAEY 



1. Preliminary tests. 



(a) As a result of a long- series of observations, it has been found 



that the assumption made by Eve and Satterly, that bubbling 

 air through the cold solution of radium bromide will remove 

 the emanation as rapidly as it is formed, is not justified. By 

 bubbling air through the solution at room temperature, about 

 27°, only about 80 per cent of the total amount of emanation 

 formed is removed. 



(b) For quantities of emanation of the order of magnitude dealt with 



in the determinations, the charcoal does not become saturated. 

 A phenomenon analogous to saturation manifests itself when 

 the charcoal is packed in a short column. The best distribution 

 of a given weight of charcoal is that obtained in a long tube 

 of small bore. 



(c) The coconut charcoal used gave no evidence of containing a trace 



of radium. 



2. The radium-emanation content of the atmosphere of Manila has been 



determined by the charcoal-absorption method. During a period of 

 eight months, we made twenty-one determinations of the amount of 

 radium emanation per cubic meter of air, the average value, expressed 

 in its radium equivalent, being 82.5 X IO-12 gram. The radium-emana- 

 tion content is subject to considerable variation, the ratio of the maxi- 

 mum to the minimum being approximately 4 to 1. 



3. In order to determine the variation of the radium-emanation content of 



the atmosphere with altitude, observations by the charcoal-absorption 

 method were taken on Mount Pauai, elevation 2,460 meters. The 

 average value obtained for ten observations was 19.1 x IO-12 gram per 

 cubic meter, as compared with 82.5 X lO-i^ gram for Manila. It seems 

 to be fairly conclusive, therefore, that the amount of radium emanation 

 in the atmosphere decreases with altitude. The range of variation of 

 the emanation content was found to be practically the same for Mount 

 Pauai as that given for Manila. 



4. For both Manila and Mount Pauai the variation of the amount of radium 



emanation in the atmosphere has been found to be fairly closely 

 correlated to the changes in the weather. Determinations made during 

 fair weather almost invariably give comparatively high values, while 

 observations taken after or during a period of heavy rains show a 

 decided decrease. 



No definite relation has been observed between the variation 

 of the emanation content and a rising or falling barometer. 

 Changes in the humidity, likewise, seem to have no effect on 

 the radioactivity of the atmosphere. The total wind movement 

 is evidently an important factor in determining the variation. 



For Manila a decided variation between day and night expo- 

 sures has been found. The ratio of the average for night 

 exposures to that for day exposures is approximately 2 to 1. 



It is our intention to continue observations on this interesting 

 phase of the problem. 



