varied between 0.1 and 3 minutes per determination. Instrumentation n-as basically similar to conTentional aqueous thermometric titrations which have recently been discussed in a review article ( 1 ) . Adaptation to fused salt media and to elevated temperatures \vas achieved by using a n automatic vertical syringe-microburet, which was positioned in toto within the top portion of an argon-filled gas space in an adiabatic titration cell. The melt titrated [called "the titrate" ( 7 ) ] was a t the bottom of the cell. The entire titration cell rested on a turntable, enclosed in an isothermal electric oven. The oven cavity (30 liters in volume) was thermostated to =kO.l" C. Random temperature fluctuations in the titrant and titrate melts were minimized to 10.0005" C. The titrant
was delivered a t a constant rate of (4.02 0.02) microliter per second with the aid of precision-machined motor driven worm-gear assembly operated by remote control. The typical temperature change in a titration was in a range between 0.01' and 0.5" C. It was monitored via a thermistor bridge (sensitivity threshold 0.00003" C.) and recorded automatically by a suitable instrument, the time scale of which was synchronously coupled with the microburet. Titration curves of chloride nith silver in fused salt solvents were similar in shape to those normally obtaincd in aqueous solutions for exothermic processes ( I , 3, 6 ) . Addition of titrant gave a rectilinear ascending trace, which leveled off in the vicinity of the equivalence point to yield a horizontal "excess reagent line." The ex-
*
Determination of Potassium Chloride by Argentimelric Precipitation Titration in Fused lithium-Potassium Nitrate" a t 158 ' C.
Initial Chloride Molality 8.615 x 10-4 2 112 x 10-3 5 205 x 10-3 1.170 x 10-2 1.985 x 10-2
a
*
Experimental E-nd Point Stoichiometry, Moles Ag+/llole C11.04 0,962 1 003
Relative Chloride, Millimoles Titration Found Error,b 70 Taken 0 0939 0,0979 +4 0.2133 0.2053 -3.8 0.5231 0.5248 +0.3 1.100 1.050 0.955 -4.5 1.985 1.980 0.997 -0.3 Mean values 0.991 -0.8 Std. dev. of mean f o . 016 lt1.5 Eutectic melt, 347, ( w . / K . ) LiXO,. Referred to theoretical equivalence point stoichiometry corresponding to AgC1.
perimental end point mas determined by linear extrapolation from the two discrete branches of the titration curve. A detailed description of the instrumentation is being prepared and will be published a t a later date. Theoretical implications of reaction enthalpies in molten salts will be discussed in a separate paper. LITERATURE CITED
(1) Jordan, J., Record Chem. Progr. 19, No. 4 193 (1958). ( 2 ) Jordan, J., Billingham, E. J., Jr., un-
published results, 1959.
(3) Jordan, J., Dumbaugh, W. M., Jr., ANAL.CHEII.30, 210 (1959). (4) Jordan, J., Meier, J., Billingham, E. J., Jr., Pendergrast, J., unpublished rpwl _ _ .t
(5) .Jordan, J., Pendergrast, J.. unpublished results, 1959. (6) Lixide, H. IT., Rogers, L. B., Hume, D. N.. ASAI,. C m x . 2 5 . 404 (1953). (7) Linghne, J. J., "El&troanalytical Chemistry," 2nd ed., p. 488, Interscience, Kew York, 1958. JOSEPH JORDAN JURG MEIER E. J. BILLINGHAM, JR. JAMES PENDERGRAST Department of Chemistry The Pennsylvania State University University Park, Pa. RECEIVEDfor review ..ipril 16, 1959. Accepted May 21, 1959. Division of -4nalytical Chemistry, Beckman dxard Symposium of Chemical Instrumentation, 135th Meeting, ACS, Boston, Mass., April 1959. Supported by the United States Atomic Energy Commission under contract AT( 30-1)2133 n ith The Pennsylvania State University.
Gas- Liq uid Pa rtition Chroma tog ra phy for Meta Is Se pa rations SIR: It has been found possible to separate metals in the form of their volatile halides by a gas-liquid partition chromatographic technique. The samples were introduced with a hypodermic syringe. The metal chlorides were protected from atmospheric moisture during the transfer by enclosing part of the apparatus in a dry box kept under a slight positive pressure of dry air. Both tin(1V) chloride (boiling point 114' C.) and titanium(1V) chloride (boiling point 136' C.) gave well defined, symmetrical bands when passed through a 5-foot, coiled, copper tube inch in outside diameter, packed with 19 grams of a mixture of 31% by weight of n-hexxdecane on Chromosorb (Johns-Manrille) . Using
1440
ANALYTICAL CHEMISTRY
helium as carrier at a flow rate of 46.0 ml. per minute and a column temperature of 102' C., the retention times of the SnC14 and TiC14 were found to be 8.30 and 19.25 minutes, respectively. Retention times were reproducible to within 10 p.p.t. The values obtained in a mixture were the same as the values obtained when each component was put through the column separately. The vapor pressures of the SnC14 and TiC14 a t 102" C. have been calculated t o be 537 and 282 mm. of mercury, respectively (1). The ratio of vapor pressures of these two compounds, 1.91, is about the same as the inverse ratio of their retention times, 2.32. This is not surprising, as no
specific chemical interaction of thesehalides with the hydrocarbon is expected. The applicability of this method of separating metals to other metals, derivatives, immobile phases, and column conditions is under active investigation. LITERATURE CITED
(1) "Handbook of Chemistry and Physics," 40th ed., pp. 2347-9, Chemical
Rubber Publishing Co., 1958.
Cleveland,
HENRY FREISER University of Arizona Tuscon, Ariz. RECEIVEDfor review May 21, 1959.. Accepted June 17, 1959.
