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RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



Table 5-3. Data for Preparation of Ca'*^ Self- absorption Curve" 



" Standard amount of Ca""^ incorporated into calcium oxalate; precipitate collected 

 in metal cups of 4.75-cm^ area. 



^ N = observed activity with indicated mass. 



No = observed activity with essentially weightless source. 



10 20 30 40 



7^mq/cm2 CaC204 (constant activity) 



Fig. 5-8. Self-absorption curves for Ca" in calcium oxalate as measured with end- 

 window and windowless counters. [From Waller L. Graf, C. L. Comar, and Ira B. 

 Whitney, Relative Sensitivities of Windowless and End-window Counters, Nucleonics, 9 : 

 22-27 (1951).] 



