qesium-137 abundance by this method seems essentially independent of the calibration coefficient of the analyzer if n is sufficiently large, because N approaches thc same broad maximum value in each case. This broad maximum value corresponds approximately to the sum of all the counts in the total absorption peak. Table I11 summarizes measurenients made on pure cesium-137 samples of different activity levels. From the ?/N, ratios, it appears that the linearity of response in this region is within the limits of experimental error. Here also, there is good agreement between t h e experimental and expected errors. Table IV summarizes measurements m a d e with different mixture ratios, M , of cesium-137 and zinc-65. Plots of the mixture pulse height distributions arc shown in Figure 6. The disparities noted between the experimental and expected errors are probably due to the fact that Equation 7 is an approximation which becomes more in error as counting rate and dead time achieve large values, as was the case for the zinc-65 in making up the mixtures according to Table I. The relationships established by Covell et al. (5’) would give a more exact statement of the expected error. Although values of R are within the limits of experimental error in every case, the pattern of departure from unity seems to be consistent for each of the three mixtures studied, indicating a possible distortion in the distribution in the region of the
cesium-137 peak in the mixture, as compared to the pure distributions. CONCLUSIONS
A technique has been described which appears capable of providing rapid, accurate, and precise quantitative interpretation of pulse height distribution data, applicable in the determination of radionuclide abundances. The method is less subjecti1.r than some of the usual graphical methods of interpreting pulse height distribution data. The accuracy and precision attainable and the number of components which can be analyzed cannot be generalized, but rather depend upon the exnct conditions of observation. The prrcision attainable is predictable and can be optimized in terms of experimental conditions. There are obvious limitations in the use of the method and particular problems should be studied carefully to determine the applicabilitj. of the technique, as well as the selection of optimum values of A , n, and AT7 in accordance \\ith the requirements for speed, accuracy, and precision. It should be possible to routinize the technique for differcnt conditions so that an ini~stiyntorcan readily select nearl!. optiinimi wlues of A , n, and N yin terms of i;ie:isiirenient and computational facilit?,. The usefulness of the mcthod can lie extended by combining it with simple chemical procedures, such as group or species separations, \vhere t,hese result in more favorable conditions for intc~pretation.
ACKNOWLEDGMENT
Radionuclide standards used in this evaluation were provided by D. L. Love and are gratefully acknowledged. The author also expresses appreciation for the valuable assistance given by M. M. Sandomire in the statistical phase of this xork. LITERATURE CITED
( I ) Bell P. R., in “Beta and Gamma
Ray bpectroscopy,” K. Siegbahn, ed., Chap. V, Interscience, New York, 1955. (2) Covell, D. F., Sandomire, M. M., Eichen, M. S., Division of Analytical Chemistry, 133rd Meeting, ACS, San Francisco, Calif., Agril 1958. (3) Heath, R. L., Scintillation Spectrometry Gamma-Ray Spectrum Catalogue,” Idaho Operations Office, IDO16408 (1957). ( 4 ) Heath, R. L., Schroeder, F., “Quantitative Techniques of Scintillation Spectrometry as Applied to Calibration of Standard Sources,” Idaho Operations Office, DO-16149, 1st revision (1957). (5) Koch, H. W., Johnston, R. W., eds., “Multichannel Pulse Hei ht Analyzers,” Proc. of Informal Con?., Gatlinburg, Tenn., September 1956, Natl. Acad. of Sci., Natl. Research Council, Publ. No. 467, pp. 182-4, 1957. (6) Lee, W., ANAL.CHEM.31, 800 (1959). (7) McIsaac, L. D., U. S. Naval Radiological Defense Laboratory Tech. Rept. USNRDL-TR-72 (1956). (8) Schumann, R. W., McMahon, J. P., Rev. Sci. Znstr. 27, 675 (1956). RECEIVED for review February 6, 1959. Accepted July 28, 1959. Presented. in part before Symposium on Radiochemical Analysis, Division of .4nnlytical Chemistry, 133rd Meeting, .4CS, San Francisco, Calif., April 1958.
S pect ro photo met ric Dete r mination of Aldoses by an Iodometric Procedure GAIL LORENZ MILLER and ANNE L. BURTON Pioneering Research Division, Quartermaster Research and Engineering Center, Nafick, Mass.
b An iodometric procedure for determination of aldos?s is describcd in which the excess of iodine is measured spectrophotometrically and a glucose solution i s used C I S the refsrence standard. In the development of the procedure, consideration was given to pH, potassium iodide concentration, reaction time, and temperature. Tests were made with pentoses, hexoses, oligosaccharides, and enzymic digests of carboxymethylcellulose. Consideration was also given to complex formation of iodine with carbaxymethylcellulose.
T
usual iodornctric procrdurc for dt+rmination of a1dosi.s consists of treating test samples n t an alkaline pH HE
17%
ANALYTICAL CHEMISTRY
of stand:ird iodinrsolution, followed, d t e r a suitabli. ~ x ~ i oofd standing. by :icidification : l i l t 1 trirk-titration with sodium thiosulf:itt> solution. This proccdurc hns bcm rc.portcd to hc :ipplicahlc t o thc cl
