empirically, was Following 1.16. analysis by gamma spectroscopy, the ashed samples were dissolved in a known volume of 1N HNO3. Stron- tium-90 was determined on an aliquot by the method of Kawabata and Held (1958), in which a combination of nitric acid precipi- tation and ion exchange procedures is used. Calcium was determined by the permanganate titration of oxalic acid and was confirmed by flame spectrophotometry, with the internal standard technique of Chow and Thompson (1955). Potassium was determined by flame spectrophotometry at 766 mu wave length and independently confirmed with estimation of potassium by titration of the cobaltinitrite with potassium permanganate (Hibbard and Stout, at 589 mit wave length. In 1933). Sodium was determined making these determinations, slit width was kept at a minimum to blue-sensitive filter was used eliminate the interference; and the sensitivity set as high as possible consistent with the reproducibility. The flame spectrophotometer was a Beckman DU equipped with a vacuum tube power supply and an oxy-hydrogen flame. The standardization procedure and general function of the system has been described by Chakravarti and Joyner (1960). In determining magnesium, was dissolved in 0.1N HCl and an aliquot of the ashed sample the solution passed through a