DIELECTRIC CONSTANT OF GERMANIUM TETRACHLORIDE BY MARY E. LEAR
The germanium tetrachloride used for measuring its dielectric constant was prepared from germanium dioxide. About eight grams of the oxide was reduced to the black powder form of germanium by a stream of hydrogen gas, washed and dried. A silica tube and silica boats were used to withstand the temperature necessary for reduction. During the reduction, a slight black mirror formed in the cool portion of the tube. The metallic germanium left in the boats was treated with chlorine gas from a cylinder of liquid chlorine, after purified nitrogen gas had been passed through to remove all air from the apparatus. The reaction was quite evident from the light appearing over the boats and a mild glow of the metal. The germanium tetrachloride condensed in the first of a series of U-tubes immersed in an ice-salt mixture. Nitr6gen gas was passed through the apparatus at the end of the experiment to sweep out the excess chlorine. A yield of about ten cubic centimeters was obtained from five grams of ge‘rmanium. The method followed was in general that of Dennis and Hancel. The product was then distilled and its boiling point measured. Using a thermometer, graduated in tenths of degrees, the boiling point read 84.40 degrees a t a pressure of 735 mm. When corrected for pressure by Young’s modulus2 and for emergent stem by the method of Rimbach3 using the table of Austin and Thwing4, the above reading becomes 86.30 degrees. For measuring the dielectric constant of the liquid, the apparatus of Drude as modified by Schmidts was set up. Three condenser bulbs of varying capacities contained the liquids used in measurement. They were standardized with benzene, thiophene free, and acetone distilled over calcium chloride. The readings for the bulbs filled with air and with benzene gave two values of dielectric constants below that of germanium chloride and mixture of benzene and acetone, according to Drudee, gave three values above that)of the chloride. Not less than five scale readings were made for each liquid. On plotting the scale readings against the dielectric constants, curves were obtained, from which the dielectric constant of germanium tetrachloride was determined directly. Results Cell I. Dielectric constant a t 30 degrees . . . 2.60 >, ” ” 30 ” . . . 2.60 Cell 2. 9, Cell 3. ” ” 30 ” . * . 2.75 J. Am. Chem. SOC.44, 3c4 (1922). Young: “Fract,ional Distillation,” 12, I 4 (1903). a Z.Instrumentenk. 10, 153 (1890). .. Austin and Thwing: ‘lPhysical hieasurements,” I 56 (1895). Schmidt: Ann. Physik. 9,919 ( ~ g c z ) Drude: .4nn. Physik. 8 , 336 (19cz). 2
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MARY E. LEAR
The average value for the dielectric constant of germanium tetrachloride is 2.65 a t 30 degrees Centigrade. Thus the dielectric constant for this compound lies between the values found for the tetrachlorides of silicon and tin, as predicted by Dr. Schlundt in his determinations of dielectric constants of inorganic so1vents.l Silicon tetrachloride D. C. at 17 degrees . . . . 2.18 Germanium tetrachloride D.C. at 30 degrees . . 2.65 Stannic chloride D.C. at 2 2 degrees . . . . . . 3 . 2 Germanium tetrachloride, having a low dielectric constant, would be expected to follow the Nernst-Thomson rule and possess no ionizing power.2 I wish to express my appreciation for the direction and assistance of Dr. Schlundt, under whose supervision the measurement was made. 2
J. Phys. Chem. 8, 130 (1904). Z. physik. Chem. 13, 531 (1894).
Chemical Laboratories Universitv of Mifisoitri and Lindenwood College.
