V O L U M E 2 4 , NO. 4, A P R I L 1 9 5 2 Theoretically, the initial buret levels should be adjusted so that t h e volume of hydrogen in each unit is the same. I n the authors’ apparatus, where the total volumes are approximately the same, the levels can be set a t zero without introducing any appreciable error. I n blank determinations in which catalyst and solvent iyere used in both sides, but no sample, unknown factors of manipulation caused the difference between the corrected init,ial or zrro reading and the corrected successive readings t o vary as much ns 0.6 Inl. on each side. However, for practical purposes the vxiation occurred in equal amounts on both sides a t any one time. One blank was xun during an 8-hour day with seven readings recorded for each side, in which the average difference in the change in volume between the two sides was 0.024 ml. This esperinient was repeated over a period of 6 days with 29 readings recorded and the average difference was 0.051 ml. (Figure 2). T h e blank determinations agree with the average error in analyses :itid shon- that the accuracy does decrease somewhat over an extended period of time, probably through diffusion of hydrogen, I n the aut,hors’ analyses the change in volume in the side used as ii blzink is a correction factor which is added or subtracted, as the c:iso niay be, from the volumeof hydrogen absorbed during reduction. co~cLusIos
Using this apparatus, it is possible to determine accurately the n t r of hydrogenation of a givrn compound as well as to determine coni1)lete hydrogenation. Samples niay he renioved after partial
717 hydrogenation, which is useful in the preparation of further derivatives. Once this apparatus is assembled and calibrated. the actual hydrogenation of organic compounds is simple and accurate. As it is permanently mounted and no hydrogen purification train is used, no time is lost in setting up complicated equipment fox anal) ses. The accuracy is 2% or better when the sample size is adjusted to absorb about 5 ml. of hydrogen. ACKNOW LEDG\IENT
The authors \yish t o acknoi\ ledge the suggestions and assistance of Rita Fox and Frances hIcCarron of Smith, Kline and French Laboratories, in obtaining the analytical data reported in thip paper. LITERATURE CITED
Doering and Knox, J . A m . C‘hem. Soc., 73, 834 (1951). Dunlop, E. C., presented before Sew I-ork -icademy of Sciences, March 25 and 26, 1949. Horning, E. C., et al., J . A m . C h e m . Soc.. 72, 4840 (1950). Johns, I. B., and Seiferle, E. J., ISD. Esc:. C“EM., .kN.%I.. ED., 13, 841-3 (1941). Prater, .A. S . ,and Haagen-Smit, A . J., Ibid., 12, 705-7 (1940). Weygand, C., and W-erner, A , J . prcikt. Chem., 149, 330-6 (1937). Zeisel, S., Monatsh., 9, 1 (1888). RECEITED for review July 10, 1951. Accepted .January 21. 19.52. P r e sented before the Division of Analytical Chemistry a t the 119th l l e e t i n g of the . i l r E R x c a s C H E J r I C a L SOCIETY, Boston, IIass.
Determination of Submicrogram Quantities of Arsenic by Radioactivation General Method and Application to Germanium Dioxide A. A . S \ l i L E S
AhD
R . D. PITE, Atomic Energy Research Establishment, Harwell, England
The limitations of existing con\-entional methods for the determination of very small quantities of arsenic make it desirable to consider any other method that offers the possibility of increased sensitivity. Using the IIarwell pile for irradiation, followed by chemical separation on carrier, as little as gram of arsenic may be determined in simple cases. In the special case of germanium dioxide, nuclear considerations prevent full realization of the potential sensitivitv; nevertheless 0.01 p.p.ni. of arsenic may be determined readily, and this level appears to cover, or at least approach, the industrial requirements for dioxide for use in diode and transistor manufacture. The radioactivation method offers specificity, freedom from “blank” difficulties, avoidance of chemical separations involving submicrogram quantities, and remarkable sensitivity.
M
.INY methods are available in xhich as little as 0.1 niicro-
gram of arsenic is determined-see Wilson (19) and Sandell ( I S ) , for summaries. The most sensitive quantitative methods so far described appear to be those of Satterlee and Blodgett (1.6) and How (‘i‘ who ),use a modified Gptzeit procedure, and I
0 3787 0 3434 0 4417 0 4168 0 4047 0 3929 0 6161 0 6127 0,3530 0 3398
< 6 X 10-0
