A SIMPLE EVACUABLE DIE FOR THE PREPARATION OF POTASSIUM BROMIDE DISCS EMIL H. WHITE Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut
SINCE
the initial report by Stimson (1)concerning the infrared spectra of compounds in potassium bromide, a number of dies for the preparation of potassium bromide discs under vacuum have been described (2-8); these, however, have been rather complicated. The following is a description of a simple and reliable evacuable die which can give crystal-clear windows of potassium bromide. The die itself is a modification of the nonevacuable die described by Jensen (8). The diameters of the die pistons (C and D) and the collar (E) in our particular die are matched to within 0.003 mm. The vacuum seal (G) is a No. 10 rubber stopper bearing a 27-mm. hole and a copper tube as illustrated. The ends of the stopper are sanded to the proper thickness, so that the upper piston (C) just enters the top of the collar (E) in the assembled die. I n operation, the collar (E) is placed around the bottom die piece and an mixture of 0.5 mg. of compound and ca. 200 mg. of dry potassium hromide is placed in the upper part of the collar. The vacuum seal (G) is placed around the collar and the top die piece (C) is carefully lowered into place. The assembly is evacuated through H (a vacuum of 0.05 mm. may be readily attained) for two minutes; the die is then subjected to a total pressure of ca. 23,000 lb. for one minute. The die is disassembled, using the wrench ( I ) On the if necessary. The disc need not be removed from the collar since the collar is grooved to fit the microcell holder of the Perkin-Elmer Infrared Spectrophotometer. If the discs are to be stored or if a number of them are to be prepared at once, they are forced out of the collar with the piston (J). The latter is threaded a t one end so that. it may be at-
VOLUME 34, NO. 1, JANUARY, 1957
tached to the ram of an irbor press (in our case, a press used for the preparation of sodium ribbon). The die is occasionally washed with water to remove traces of potassium bromide (which cause sticking) and then dried thoroughly; it is stored in a desiccator when not in use.
A and 6. Circula. Steel plates; C and D, Steel Rod. (AISI.52.100, nilrdonsd to 60 R O C ~ W ~ T.I. II pree. it into A and 6. A + c canw e Made ae s Single U n i t ( 8 ) . F. End Vi- of E (29 mm. 0.d.); G. Rubber V-uum Seal; H. CWP- Tub.: I. Wrench for Colla. E: 3. Piston
(1) STIMSON, M. M., A N D M. J. O'T>ONNELL, J . Am. Chem. h e . , 74, 1805 (1952). (2) ANDERSON, D. H., A N D R. G . SMITH,~ n a l Chem., . 26, 1674 (1954). (3) FRENCH, R. O., el al., J . Phys. Chem., 58,805 (1954). (4) INGEBRIGTSON, D. N., A N D A. L. SMITH,Anal. Chem., 26, 1765 (1954). ( 5 ) KIRKLAND, J: J., Anal. Chem., 27, 1537 (1955). (6) PERKIN-ELMER CORP.,Instrument News, 4, No. 3, 1 (1953). (7) SCAIEDT, V., AND H. REINWEIN, Z. Natu$omh., 7b, 270 (1952); SCHIEDT, V., Z. N a t u r f m h . , 8b, 66 (1953). (8) JENSEN, J. B.,Aeta Chem. Scand., 8,393, 1088 (1954).
