Carl 0. Thomas'
and Hilton A. Smith Universitv of Tennessee Knoxville
II
A Simple Katharometer Design
W i t h the rapid growth of the gas-chromatographic technique in recent years, there has been a parallel emphasis on the design of thermal conductivity cells (katharometers) for use as detectors. The design theory for hot-wire katharometers has been discussed thoroughly (1,8, S),and information on the characteristics of thermistors also is readily available (4). However, the actual construction of a satisfactory katharometer often requires skillful use of glass blowing or machine shop practice. In order to circumvent these construction difficulties, the simple katharometer shown in the accompanying figure was designed. No glass work is required and the only necessary tools are a drill, hacksaw, file, tap, and soldering facilities. The katharometer block is cut from a piece of brass rod stock. Axial holes, 1/8-in. in diameter, are drilled to provide gas paths. At one end of the block the holes are reamed for a short distance with a larger drill and then tapped to accept standard brass fittings. The gas paths for the reference and the sensing sides are identical and are as indicated by the arrows, W. The up and down paths for each half of the cell are joined by flat brass caps, soldered to the katharometer block a t 2. The horizontal path in each cap is prepared by chemical etching after masking the piece with paraffin. The additional time of gas residence within the block provided by the U form of the path allows the sample to come to temperature equilibrium with the katharometer. Holes are drilled from the side of the block to accept premounted matched filament (5) or thermistor (6) detectors. For our work, thermistors were used. The volume of each thermistor cavity was approximately 0.6 ml. The thermistor flanges were hacked at X with plugs of Sauereisen cement. For operations at room temperature or below, a copper cooling coil can be soldered directly to the katharometer block. For high temperature operation an electric-cartridge heater (7) and a regulating device (8)may be inserted into two holes drilled directly into the block. This katht~rometerwas designed in connection with worlt s u p parted hy the U. S. Atomic Energy Commission. ' Present sddress. Bell Telephone Laboratories, Murray Hill,
N. J.
The katharometer was constructed originally for studies on the chromatographic separation of hydrogen isotopes (9). However, the design should be applicable for a variety of problems.
W = DIRECTION OF GAS FLOW X =APPROXIMATE
POSITION
OF THERMISTOR B E A D
SCALE
Kdharorneter for gar chromatography.
Literature Cited (1) KEULE~~ANS, A. I. M., "Gas Chromatography," Reinhold Publishing Co., New York, 1957. (2) DESTY,D. H., Tapour Phase Chromatography," Butterworths Scientific Publications, London, 1957. (3) SHAKESPEARE. G. A,. PIOC.P ~ I I SOC. S . (London).A33. 163 (4) (5)
(6) (7) (8) (9)
"T'hermistor Data Book," Victory Engineering Corporation, Union, N. J. Gaw-Mac Instrument Co., Madison, N. J. Victory Engineering Corp., Union, N. J. Chromalox heater, Edwin L. Wiegrtnd Co., Pittsburgh, Pa. Fenwal thermoswitch, Fenwal, Inc., Ashlend, Mass. . 63, X27 THOMAS, C. O., AND SMITH, H. A., J . P h ~ s Chem., (1959).
Volume 36, Number 10, October 1959 / 527
