FILLING

,r.I~.i"THERMOCOUPt-E WIRES

A

- - ---~THERMOCOUPLE WIRES GOING IN BETWEEN THE TWO IRTRAN WINDOWS.

FIG. 2. Teflon adapter of Fig. 1. The threaded par t (A) screws into one of the filling ports of the cell.

compartment. This equilibrium is not affected by the energy of the ir beam. No difficulty was experienced in filling the cell through the side hole of the Teflon adaptor so that this method of temperature measure- ment could be used with nonaqueous solutions by passing one thermocouple wire through a Teflon adap- ter in each of the two filling ports thus eliminating the need for insulating varnish on the wires.

The financial support of the Defence Research Board (J. L. T.) and of the College militaire royal de Saint-Jean (M. C.) is gratefully acknowledged as is the technical assistance of Mrs. Joan Thompson.

1. W. J. Ports Jr., Chemical Infrared Spectroscopy (Wiley, New York 1963), Vol. I, p. 248.

2. M. S. Smith and P. A. D. de Maine, Can. J. Chem. 41, 812 (1963), and references cited.

3. D. J. Aseino and J. F. Schneider (Engelhard Industr ies Inc.), paper presented at the Four th Symposium on Temperature, Columbus, Ohio, March 1961.

several commercially available cells which partially meet these requirements but all of these have some undesirable features, such as ground glass stopcocks which require silicone or hydrocarbon grease. There- fore, we have devised and wish to describe a fairly inexpensive cell which meets the above specifications.

The construction of the gas cell is shown in Fig. 1. The barrel is a product of the Cajon Corporation and was machined from a hexagonal brass rod 3~--~ in. long to form an extra long bodied 1½ in. i.d. Caion Ultra- Torr (Cajon Corp., Solon, Ohio, Catalog No. 24UT-6) union. The first cell body required a support sleeve which was made so that the windows would not be withdrawn into the cell upon evacuation. However, the cell body can be easily fabricated such that the normal depth of the tube receiver will be reduced from ½ to ~ in., obviating the need for the support sleeve. The cell barrel is equipped to accept a Cajon O-ring connector (Catalog No. 6UT-1-9/16-18-OR) which pro- vides a very convenient fitting for a valve or tube. We use Kontes Teflon or Kel-F greaseless valves which easily connect to this fitting. To increase its inertness, the cell barrel was coated with Teflon in a routine manner. The body was first cleaned by sandblast and then sprayed with a thin (~0.001 in.) film of duPont No. 851-204 industrial finish Teflon. I t was then air dried for approximately 24 h and followed by baking at 725°F for 15 min. The cell is rapidly cooled from this temperature by quenching in water.

The most distinguishing feature of this cell is the manner in which the optical window is mated to the cell barrel. The seal is essentially the Ultra-Torr fitting and is accomplished by extruding an O-ring down on a beveled surface and against the edge of the optical disk. Because the force is applied equally about

A Novel Infrared Gas Cell

Albert B. Harvey, Fred E. Saalfeld, and Charles W. Sink* Naval Research Laboratory, Washington, D. C. 20390

(Received 30 January 1970; revision received 6 March 1970)

INDEX HEADINGS: Infrared ins t rumentat ion; Gas cell.

In the course of a vibrational study of methanetel- lurol (CH3TeH) a need arose for a short path (ap- proximately 10 cm) ir gas cell which uses no stopcock grease, no wax to seal the windows, presents a rela- tively inert inner surface, and can be rapidly assembled and disassembled. These requirements arise from the fact that methanetellurol and many similar com- pounds are unstable, decompose, and/or absorb readily in the presence of active surfaces, stopcock grease, and sealing wax. These materials are generally used in the construction of conventional cells, partic- ularly the homemade variety, and their presence often accounts for experimental difficulties. There are

* N R C - N R L Postdoctoral Research Associate.

FIG. 1. High vacuum infrared gas cell. Pe r t inen t dimensions, in inches, as follows: over-all length 4½; pa th length 3] ; i.d. 1]; window diameter 1½; Vi ton O-ring i.d. 1 !2, o.d. 1]; valve s tem

o.d. (with 4 m m bore).

4 6 6 Volume 24, Number 4, 1970

the circumference of the disk, window distortion, which seriously impairs window polishing, is markedly reduced.

The advantages of this cell are (1) reproducible high vacuum seals, (2) rapid removal and remounting of windows, (3) relatively inert barrel surface, (4) no grease, wax, or other absorbing and/or decomposition promoting materials, (5) unbreakable cell body, and (6) relatively low cost. Some disadvantages include (1) much heavier than conventional glass cell (how- ever, the cell may be constructed of nylon which would reduce the weight considerably; the cell body may also be constructed of stainless steel or Teflon but at a substantially higher cost) ; (2) the edges of optical windows should be relatively smooth, although most standard factory disks meet this requirement; (3) the

window material should be at least 5-6 mm thick, especially for the more brittle KBr and NaC1 disks; and (4) the cell should not be used at pressures greater than 1 arm unless it is modified to protect against the possibility of discharging the windows.

We feel this cell has wide industrial and academic applications where a cell capable of high vacuum, chemical inertness, and ease of assembly and mainten- ance is desirable.

We should like to thank Cajon Corporation of Cleveland, Ohio for construction of the cell. We are also indebted to Ray McGarvey of Potomac Valve and Fitting, Inc. for valuable suggestions about design and construction of this cell as well as for making arrangements for construction by the Cajon Corporation.

Author Index

Name Page No.

Albarino, R .V. 418

Avni, R. 406

Baldwin, J . M . 429

Barylski, J. R. (with G. J. Thomas, Jr.) 463

Blackburn, W. H. (with T. B. Griswold) 460

Boukobza, A. (with R. Avni) 406

Brown, F. W. (with A. F. Dorrzapf, Jr.) 415

Burnham, C .D. 411

Burns, G. L. (with W. W. Moore, Jr.) 457

Cormier, M. 465

Daniel, B. (with R. Avni) 406

Dennen, W. H. (with T. B. Griswold) 460

Dorrzapf, A. F., Jr. 415

Fabbi, B . P . 426

Ferraro, J. R. (with G. V. Subba Rao) 436

Griswold, T .B . 460

Harvey, A.B. 466

Haynes, L.V. 452

Horrocks, D .L . 397

Hyman, H . H . 464

Koehler, R .A . 455

Kowalski, T. (with C. D. Burnham) 411

Krasniewski, J. (with C. D. Burnham) 411

Name Page No.

Lauterbur, P .C . 450

Moore, C. E. (with C. D. Burnham) 411

Moore, W. J. (with B. P. Fabbi) 426

Moore, W. W., Jr. 457

Morgan, F. J. (with R. A. Koehler) 455

Popov, A. I. (with H. H. Hyman) 464

Quarterman, L. A. (with H. H. Hyman) 464

Rai, D. K. (with V. N. Verma) 445

Rao, C. N. R. (with G. O. Subba Rao) 436

Reid, L. R. (with J. P. Smith) 420

SaMfeld, F. E. (with A. B. Harvey) 466

Salovey, R. (with R. V. Albarino) 418

Sazavsky, C. D. (with L. V. Haynes) 452

Schneider, B. (with J. Stokr) 461

Sink, C. W. (with A. B. Harvey) 466

Smith, J . P . 420

Stokr, J. 461

Subba Rao, G.V. 436

Surles, T. (with H. H. Hyman) 464

Tashbar, P. W. (with W. W. Moore, Jr.) 457

Thomas, G. J., Jr. 463

Thompson, J. L. (with M. Cormier) 465

Verma, V.N. 445

APPLIED SPECTROSCOPY 467