Removing the "Art" from KBr Wafer Preparation: An Improved Procedure, *9,,6
Use of the Wilks Mini-Press1for prepamtion of KBr wafers for infrared analysis
,ICY
socm
WYMW
?UTE
of solid samples has facilitated this operation in the organic laboratory. Improvements of the manufacturer's suggested procedure and equipment have been utilized for our organic laboratory program. The primary problem previously encountered is that it was extremely difficult for students to learn how much torque to apply when tightening the press bolts With excessive torque some bolt heads were twisted off; when insufficient torque was applied the result was an opaque wafer or none at all. Some students do not have the physical strength to apply the proper amount of torque. I/OLIJnlnJ IIrn "OLE D l l i l l D l Y I O F L ~ T E W E OCOPPER T U ~ C . The "bench-top wrench" which the manufacturer provides as a hexagonal socket to be fastened on a work surface for holding the lower bolt of the press fixed during tightening does not stand abuse. I t is a shallow socket, and unless moderate care is used when torque is applied to the top bolt, the lower bolt slips from the socket, generally burring it in the process. As the socket hecomes worn, the bolt beads gradually also become rounded bexagons. As with any method for preparing KBI wafers, the weighing of KBr and sample requires time. Loss of material and millnee 7 ~ occur ~ ~ during ~ n ~e weiehine ~ .. and the oraeess makes balances unavailable for other oumoses. In an attempt 11, inrwore the productivity ofvtudents m the organic laboratmy and to decrease student frustratims. to reduce thr numher ofweighing operations, to conserve KBr and to increase the lifetimp of press parts. a modified method thr labnratmy c l a ~ r in a which it is u s 4 are lame, a prwedure requiring for use of the Mm-Press has h e n developer. B-use less than five minutes per wafer preparation was considered necessary. These objectives are accomplished by eliminating the weighing of KBr, making easy the application of know and proper amount of torque in the pressing process and by improvement of the socket mounted on the work table. (*4%) bv use of a small Anhvdraus KBr can be ranidlv and reoroduciblvdisoensed in 100to 300 milligram - auantities . ladle. ~n;nenoensive.~.~~ non-hreikable ladlewas oreoaredbv flattenine one inch at each end of a &in. oiece bfli,-in. comer tubing, then s k v i n g n used z!;: cal~herahurtrifleranridge inma hole&illed stoneof rheends raer f i k r e ~~i1li.y . une-ihird of the cartridge with silver wldrr l ~ f Rt volumr that would deliver 20c mg of KHr. The amount of d d r r dead-volume in the cartridge must be adjusted to allow for the grain size of the KBr used. Inasmuch as one 500-g bottle of KBr should provide approximately 2500 wafers,frequent modification of solder volume should not be necessary. Reproducible application of torque to the top bolt of the Mini-Press is obtained by use of a torque wrench (cost of ~ Y proper tightening. Ad422.00). The leverape orovided bv this wrench allowed even the frailest of students to ~ D D the monitin& the instr;c
