number of (Ag+-excess) and ( X - excess) analyses would be nearly the same and any error due to the adsorption effect indicated above would most likely cancel out. How ever, in the exceptional case of a series of analyses in which the dis tribution of analyses between the two types is one-sided or in which the analyses are all of one type, the possibility of a small error exists. A good illustration of this is to be found in the determination of the atomic weight of Cd by Baxter, Hines, and Frevert. This deter mination comprised eight analyses of CdBr2, of which seven were of the (Ag + -cxcess) type and one of the (X"-excess) type. The S/Ag ratio of the latter was 6.1 parts in 105 lower than the mean value of the other seven analyses. Regarding this result Baxter, Hines, and Fre vert state that it differed "so markedly from the others that, al though no reason for the difference is known, it is rejected in comput ing the final average." In terms of atomic weight units the rejected analysis was 0.02 unit lower than the others. From the standpoint of the present discussion the atomic weight of Cd which Baxter et al. ac cepted is possibly too high by 0.01 unit because it is derived from only (Ag+-excess) analyses.
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ACKNOWLEDGMENT The author acknowledges with gratitude a grant from the National Science Foundation, part of which was in support of the present study.
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LITERATURE CITED (1) Johnson, C. R , J. Phys. Chem. 35, 830 (1931). (2) Nier, A. O., Science 121, 737 (1955). (3) Scott, A. F., Bettman, Max, Chem. Reus. 50, 363 (1952). (4) Scott, A. F., Hurley, F. H , Jr., / . Am. Chem. Sac. 59, 1297 (1937). Λ more detailed form of this paper has been deposited as Document Num ber 6813 with the ADI Auxiliary Pub lications Project, Photoduplication Service, Library of Congress, Washing ton 25, D. C. A copy may be secured by citing the document number and by remitting $ 10.00 for photoprints, or $3.50 for 35 m m . microfilm. Advance payment is required. Make checks o r money orders payable to: Chief, Photoduplication Service, Library of Con gress, Washington 25, D. C.
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VOL. 33, NO. 9, AUGUST 1961 · 3 1 A
