V O L U M E 2 6 , NO. 6, J U N E 1 9 5 4
971 determined, are shown in Table I. The spectrometer is adjusted to the angle of the element t o be determined, and the times required for several successive counts are recorded. The times required for the several counts taken are averaged and calculated as counts per second. The factor for instrument sensitivity is applied, if necessary, and the concentration of the rlement k i n g determined is found from the calibration curve.
0
z
RESULTS
P
The results for a series of calcium, zinc, and barium samples arc shown in Table I. The accuracy of the s-ray data for these and other determinations was found to be at least equal t,o chemical methods. The method is capable, if sufficient counts are taken, of yielding accuracies within 2 or 3% of the barium and calcium, when present in concentrations greater than 0.05%, and within 1 to 2% of zinc in concentrations greater than 0.005%.
d
!
ACKN0WLEDC)I ENT
The authors are indebted to Fred Behr of S o r t h American Phillips Co. for assistance and advice, to several members of the staff of Sinclair Research Laboratories for assistance, and to S . J. Gothard and George Entwistle of Sinc.lair Refining Co. for inaugurating this etudy. LITERATURE C I T E D
% CALCIUM Figure 7 . Calibration Curve for Calcium Using a \1o1> bdenum Tube at 50 Kv. and 40 3Ia. w-ith Helium t o approximately GOO ml. per minute a f e n minutes before counting determinations are to be made. The sample dish is carefully filled to a fixed level and inserted in position under the s-ray tube. The scaler is set for fixed count operation, the number of count? i n keeping with the accuracy desired. The statistics of counting a r e discussed by Birks et al. ( 2 ) . Spectrometer angles, using a rork salt crystal for a d spacing of 2.810 -2. for the elements t o be
(1) B a r r e t t , C. S., "Structure of l l e t a l s . " 2nd ed., S e w Torli, l I c Gran--Hill Book Co., 1952. ( 2 ) Birks. L. S..Brooks, E. J., Friedman. H., and Roe, I
