150 The Philippine Journal of Science m? 



pie had been taken, usually within thirty minutes, and in no 

 case after more than three hours. The arrangement of the ap- 

 paratus is shown in Plate I, fig. 2. 



The procedure in an ordinary field determination was as 

 follows : The instrument was charged, and the natural leak was 

 determined in the usual manner. The shaking can, containing 

 a fresh-water sample, was then held vertically and open, until 

 the water had drained to the level of the lower stopcock. The 

 can was then closed, vigorously shaken for about one minute, 

 and placed in the circulatory system as shown in Plate I. 

 The air and the emanation in the system were circulated by 

 means of a small rubber bulb for two minutes to ensure equal 

 distribution of the emanation. The stopcocks on the ionization 

 chamber were then closed, and fifteen minutes later the leak 

 was determined, as previously described. 



Determination of radium content. — Samples of typical waters 

 were brought to the laboratory, sealed in proper vessels, allowed 

 to stand for a month, and tested for radium content. The 

 method of procedure was identical with that described with the 

 standard solution, except that 400 cubic centimeter Jena flasks, 

 equipped with aspirator tubes, were used to hold the water in- 

 stead of the tube used for the radium solution. About 250 

 cubic centimeters of water were used in a determination. In 

 some cases, when larger quantities of water were available, as 

 much as 15 liters were evaporated to 250 cubic centimeters, 

 acidified with ^hydrochloric acid, sealed in Jena flasks, and 

 tested. 



Calculation of results. — Radium-emanation content was cal- 

 culated in terms of the weight of radium that would produce 

 the leak noted when in radioactive equilibrium with its own 

 emanation, and is expressed as grams X 10- 12 per liter of water. 



The apparatus constant was calculated from the formula 9 



a== 1000 fr+fc+^ +ffi (1) 



in which 



w is the quantity of water, in cubic centimeters, under investiga- 

 tion; 



l lt l 2 , and l. A are the quantities of air (in cubic centimeters) 

 in the shaking vessel, in the respiration system, and in the 

 ionization chamber, respectively; and 



a is the fraction of the emanation remaining in the water after 

 shaking. 



' J Schmidt, H. W., op. cit., 565. 



