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MINOGREENAND PAULH. ROBINSON
VOl. 57
THE REFRACTIVE INDEX OF GERMANE1 BY MINOGREEN^ AND PAUL H. Lincoln Laboratory, Massachusetts Institute of Technology, Cambridge, Mass., and Department of Chemistry of the Polytechnic Institute of Brooklyn, Brooklyn, N . Y. Received April 16, 1863
The refzactive index of germane has been determined. The values obtained are 1.0009095 at 5484 1.and 1.0008940 in the 5893 A. region, The atomic refraction of germanium is given as 8.95 cm.8
The difference in refractive index between hydrogen and germane has been used as the basis of a method for assaying GeH4-H2 ratios. The calibration of the apparatus entailed the preparation of a quantity of pure GeH4 for making up known GeH4-H2 mixtures. In the course of this work it became a relatively simple matter to determine the refractive index of GeH4, no measured value for which has been reported in the literature. The GeHr obtained4 mas purified by trap-to-trap distillation under high vacuum until it gave vapor pressures agreeing with Paneth’s values6 at two different temperatures. Measurements of refractive index were made using a Rayleigh-Zeiss interferometer the detailed construction and use of which is described e1sewhere.B~~The body of the instrument mas carefully insulated in order to avoid any effect due to rapid room temperature changes. A double cell 500 mm. in length was used; one chamber of the double cell was evacuated and the other chamber was filled with GeH4 a t a known temperature and pressure. A mercury filled U-tube absolute manometer, with 20 mm. diameter limbs, was used for measuring pressure. The meniscuses were illuminated according to the method of Beattie and co-workers*in order to (1) The research in thie dooument was supported jointly by the Army, Navy and Air Foroe under contract with the Massachusetts Institute of Technology. (2) Staff member, Lincoln Laboratory, Massachusetts Institute of Technology. (3) Thia work has been done as part of a thesis submitted in partial fulfillment for the requirements for the degree of Master of Science. (4) Metal Hydrides, Beverly, Massachusetts. (5) F. A. Paneth and E. Rabinowitsch, Ber., 58B. 1138 (1924) ( 6 ) C. Candler, “Modern Interferometers,” Hilger and Watts, London, 1951. (7) L. H. Adama, J . Wash. Acad. Sci.. 5 , 265 (1915). A m . Acad. Arts and Sci., 74,327 (1941). (8) J. A. Beattie, et al., PTOC.
avoid errors due to parallax. The distance between the mercury levels was measured using a precision cathetometer. Light of two different wave lengths was employed. One source was a sodium arc lamp with most of the light intensity in the 5893 A. region (lines ~1 and DZ), and the other was a mercury arc used in conjunction with a multilayer narrow band filter which isolated the 5484 4.line.
The refractive index of GeH4, a t two different wave lengths, was measured over the pressure range 2 to 10 cm. of mercury and no perceptible deviation from linearity between pressure and refractive index was observed. The data in Table I are in each case the average of ten determinations, corrected to 0” C. and 1 atm., the deviation quoted being the standard deviation. TABLE I REFRACTIVE INDEXOF GeHd AT 0’ C. AND 1 ATM. Wave length,
5484 5893
A.
Refraotive index
1.0009095 f 2.3 X 10-6 1.0008940 f 1.6 X 10-6
The mole refraction of GeH4 for the D-lie is 13.35 0.04 C M . ~ . Taking 1.100 as the atomic refraction of H, the atomic refraction of Ge is found to be 8.95 f 0.04 cm.*. Calculations from refractive index datag for tetraethylgermanium gives 8.97 crns3,and for germanium tetrachloride 7.60 cm.*.l0 f
(9) D. L. Tabern, W. R. Orndora and L. M. Dennie, J . Am. Cham. Xoo., 47, 2039 (1926). (10) A . W . Laubengayer and D. L. Tabern, THIBJ O ~ N A L 30,1047 , (1926).
