Michael J. Clarke
and David L. Venezky Naval Research Laboratory Washington, D. C. 20390
Teflon Mixing Vial for Handling Solids for Infrared S ~ ~ C ~ ~ O S C O P Y
Potassium bromide pellets used in iufrared epectroscopy are commonly made by dispersing the sample through the potassium bromide by means of a small vial shaken rapidly in a Wig-L-Bug' apparatus. For school and industrial use where many samples are run, there are commercially available polystyrene vials which are both economical and convenient. We have found, however, in studies of the infrared region associated with the C-H stretching modes that small amounts of polystyrene from the vials were introduced A
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Figure 1. Infrared spectra of potassium bromide pelloh mode using: A, Teflon mixing vial; 8, Polystyrene mixing viol; C,Teflonmixing *id, 1.42 X 10-6m ethylenedinitrilotetramcctic acid; D, Polystyrene mixing viol. 1.42 X i O - 6 m ethylenedinitrilotetraocetic mid.
458
/
Journal of Chemical Educofion
F l/2"+
into the potassium bromide mixture. Consequently, when long mixing times (1-2 min) were required to adequately disperse the sample throughout the potassium bromide, absorption bands in the infrared spectrum attributed to the plastic vial tended to obscure the desired C-H stretching modes of the sample (Fig. 1). Substitution of stainless steel vials for the plastic vials, when long mixing times were needed, resulted in a powdered mixture which caked in the vial and, we feel, contributed to the formation of opaque pellets. A type of vial (Fig. 2) which surmounts these problems can be easily made from a '/rin. Teflon rod. We have found that a vial of this material used with a 7/82-in.Teflon ball-pestle will not introduce any detectable amounts of polymer into the sample and thus the vial material will not evidence itself in the infrared spectrum. The Teflon vial may be easily cleaned by wiping the inside with a cloth or large pipe cleaner. Since the Teflon vial is relatively soft, it may be necessary to powder hard crystalline materials in a steel vial before mixing with potassium bromide in a Teflon vial. A vial made with the specification indicated in Figure 2 will fit the usual Wig-L-Bug models (5A or 3A) found in most spectroscopy laboratories. However, the vial will hold better on the machine if the "plasticvial adapter" is used.
Figure 2. Dimenlions of mixing viol made from %-in. diameter Teflon md.
'Manufactured by Crescent Dental Mfg. Co., 7750 W. 47th St., Lyons, Ill. 60534.
3/16"
W
