APPENDIX I STANDARDS CALIBRATION Calibrated standard sources were supplied to this group by Analytical and Standards Branch of Chemical Technology Division to allow checks to be made of the relationship between area of total absorption peaks and their eeft associated photon intensities, and to provide standards of known energy for record by record energy calibration. The calibrated standards used were 75.6 (+4 percent) microcuries of Na’ 22 ana 145 (£5 percent) microcuries of Hg“03, The standards were calibrated on May 18, 1956. In order to use these standards to check the correct- ness of the I/A versus E curves, corrections had to be made in the source strengths listed. In the case of Na®@ the standards were calibrated in terms of positron emission alone, so that to arrive at the 1.28 Mev photon intensity, account had to be taken of the 6to1l percent electron cap- 15,16 ture wl? When this correction is applied, the original 1.28 Mev photon source strength becomes 80.4to 84.9 "microcuries” or 2.97 X 10° to 3.14 x 10° photons per second. To compare this number to that obtained by multiplying the area of the total absorption peak by I/A for 1.28 Mev, the area must first be found by extrapolating the decay curve pack through the calibration date. 350 This area is 1.54 (+2