A Readily Constructed Long Path-Length Cell for Infrared Spectroscopy The high cost of commercial long path-length ir cells may deter small schools from their purchase, particularly since opportunities to use them
method therefore has some advantage over the more obvious way of producing a cheap long path-length cell by permanently cementing a pair of NaCl or KBr plates to a suitable spacer.' Nor is any cement used, thus avoiding one source of contamination. A circular groove, semi-circular in cross section, is machined into one O-RING C~LLAR face of a barrel, to accommodate a 3/32in. neoprene O-ring 3/d-in. O D . Other materials andlor minor differences in dimensions might be employed. A 'Is-in. MODIFIED BARREL diameter fillinglemptying hole is then drilled through the barrel 1's in. from this face. Here again the dimensions were determined by the availability of suitable Teflon stoppers. Next, a KBr window is formed in the barrel in the usual way. A second window is formed within a second, similarly modified EXPLODED PLAN VIEW OF CELL COMPONENTS barrel, and the cell obtained by elamdng . .the two barrels together in a holder. The holder consists of a base plate, two collars and two bolts. The 1Y-in. diameter collars have 1-in. diameter openings drilled oartlv, throueh them to accommodate the barrels. The two 2-in. 8-32 bolts oass throueh one collar and screw into hole4 tapped into rhs ircond rollnr. In ourcnse this second rollnr wns mode an incegrnl part 18f the :I X 2 X '72-in. base plate. t ~ i t rw d d hen slmplrr mnrhin~ng101, to h a w t w o arparnte cdlari, holtinl: the second to the basr plate. Cells produced in this way have a path length of approximately 15mm and have proved suitable for demonstrating the existence of monomeric and hydrogen bonded dimerie farms of alcohols, acids and hydroxy acids in dilute s ~ l u t i o n . ~
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'Davies, M. M., and Sutherland, G. B. B. M., J. Chem. Phys. 6,755, (1938).
2Ceorge, W. O., Green, J. H. S., and Pailthorpe, D., J. Mol. S t r u t . , 10,297, (1971).
Mount Allison University Saekville, N.B., Canada EOA 3 C 0
Douglas H. G r a n t
Volume 57, Number 5, May 1980 1 389
