the DK-2. A 1.5-volt battery was connected across the ends of the absorbance slide-wire of the DK-2 pen, and the potential between one end of the absorbance slide-wire and the wiper was used to drive an auxiliary strip chart recorder. The fastest time constant of the DK-2 was used. The n al-elength interval between 1650 and 2200 A. was scanned in a period of 20 seconds. At the end of 20 seconds, the direction of wavelength scan \\as reversed. The bqinning of each scan was indicated on the simultaneously recordcd t h c r n d conductance record (bottom curve of Figure 9). Only one component of the gasoline was unambiguously determined in this n a y . Coniponcnt 45 (Figure 8) \vas readily identified in scan 44 of Figure 9 as naphthalene.. By repeating the chromatograph and turning the bypass valve (Figure 1) a t the time the thermal
conductance record reached the interval labeled 44 on Figure 9, the fraction was trapped in the absorption cell, and its spectrum could be recorded easily. The spectrum was almost identical to Figure 5. Other components of the gasoline could undoubtedly be identified if a longer column of greater resolution were used. A “library” of far-ultraviolet reference spectra would be needed. While many of the compounds found in gasoline do not possess spectra exhibiting sharp absorption bands, the exact wavelength of the absorption varies considerably and could assist identification. LITERATURE CITED
(1) “Handbook of Chemistry and Physics,” C. D. Hodgman, ed., 41st Ed., Chemical Rubber Pub. Co., Cleveland, 1959.
(2) Helm, R. V., Latham, D. R., Ferrin, C. R., Ball, J. S., ANAL. CHEM. 32,
1765-7 (1960).
( 3 ) Johnstone, R. A. W.,Douglas, A. G., Chein. & Ind. (London) 1959, 154.
(4) Jones, L. c.,Jr., Taylor, L. CHEM.27.228-37 (1955).
w., ANAL.
Kaye, W. I., Proceedings, Fifth International Instruments and Measurements Conf., 1960. ( 7 ) Kaye, W. I., A p p l . Spectroscopy 15, 89-95 f 1961’1. (8) Ibid.,‘p. 130-44. (9) Lichtenfels, D . H., Fleck, S. A., Burrow, F. H., Coggshall, N. D., ANAL. CHEM.28, 1376-9 (1956). (10) Potts, \T7. J.. Jr., J . Chem. Phys. 20, 809-10 (1952). (11) Swan, T. H., Mack, E., Jr., J . Am. Chem. Soc. 47, 2112-16 (1925). RECEIVEDfor review May 8, 1961. Accepted December 11, 1961. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, March 1961.
Correlation of Microwave Absorption and Moisture in Polymers SIR: Some microwave transmission mensuremepts nere made at 3 cm. to determine the correlation with moisture in rubber bales (28 X 14 X 7 inches) consisting of a copolymer of butadiene and styrene (specifically GRS-1500 and GRS-1712-type rubber). The absorption of radio frequency power as a function of moisture concentration is a n order of magnitude stronger than can be accounted for on the assumption that the moisture exists in the form of small, roughly spherical pockets of water dispersed in the voids of the rubber bale. The strong absorption can be reconciled with a moisture distribution consisting of thin surfaces or filaments. The direct current conductivity of the bales was very low, showing t h a t the moisture paths were discontinuous. Typical data are s h o m in Figure 1. The slope varied with bale temperature and rubber type. Such variations are to be expected because the relaxation absorption spectrum for liquid water shifts not only with temperature changes but also with changes in the concentra-
Figure 1 . Plot of In transmission vs. per cent moisture a t room temperature for
GRS-1712
t
-b 0 -7
0.2
tion and type of polar and ionic compounds which were undoubtedly dissolved in the moisture. The microwave system included transmission and receiving horns plus a collimating device Of nonreflective material which directed the radio frequency
0.4
0.6
0.8
1.0
1.2
1.4
1.6
power through the %-inch dimension of the rubber bale. JACK MERRITT Shell Development Co. Emeryville, Calif. RECEIVED for review xovember 20, 1961. Accepted December 5, 1961. VOL. 34, NO. 2, FEBRUARY 1962
0
293
