Preparation of Compounds for Infrared Spectrometry MICHAEL HACSKAYLO Crystal Laboratory, The Harshaw Chemical Co., Cleveland, O h i o
For the identification of impurities in synthetic cr?stals, the rapid heating of inorganic compounds o n a sodium chloride plate was conceived. This method proved successful for t h e identification of the compounds. Later, this niethod was extended to the organic compounds. The sample so prepared exhibited well-resolved absorption spectra. The spectra were free of excessive scattering a t the shorter wave lengths, a n d extraneous mulling agent or solvent bands. The compounds for infrared spectrometry can he prepared for qualitathe analysis in a short time with relatite ease. While the sample is brought to the proper state for absorption measurement, i t is also s i m u l t a n e o u 4 ~ mounted on the plate, thus providing a holder for the compound. This method can be applied to insoliihle as Me11 as soluble compounds.
S
ISCE the modern infrared spectrophotometer can autoni:ili-
cally record infrared spectra of chemical compound8 in allout tv enty minutes. i t is desirable to obtain a method of 1irep:irin.g a large number of compounds n.itli the same rapidity.
EXPERIMENTAL PROCEDb R E
Equipment. The sodium chloride plates synthetic Harshan- crJ-stds whicli cotitniiird
from :il,-oi,ption band
17-e~ prepnrei:l 110
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SODIUM O H L O R I D E P L A T E
-eo-
Man>.investigators 1i:ivc u s d the1 rorivc~ntioualNujol mixture (2, 5 ) and dried powder ( 1 ) mi.thoils for thp statiy of absorption spectra. Difficulties arise, howerer! in bringing thc conipounde into a satisfactory state for absorption spectra me:tsurcments. The particle eize of the compounds must be either 1:wge enough or small enough to prevent excessive scattering and still transmit sufficiently for absorption measurements. Henry ( 1), Pfund (6, 7 ) and others have shown that to olitain a satisfactory spect r u m from the s m d l particles, t,he diamcter of the particle must he less than the wave length at v-hich the absorption hand is being measured. llethods, n-hich have 1 J w n used to reduce the compounds to the required particle eize, arc’ rather tcldious If not complicated to perform. This paper describes a method of preparing compounds iii such a manner t h a t n-ell-resolved spectra can be obtained n-it11 considerable ease. T h e compounds are deposited as :t solution or suspension on a heated sodium chloride plate.
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POTASSIUM T H I O C Y A h A l E
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Figure 1. Infrared Spectruni of Kater-Soluble Potassium Thiocyanate Deposited on a IIeated Sodium Chloride Plate I h r upper curvc
shows
the background of the sodium rhlnride plate
V O L U M E 26, N O . 9, S E P T E M B E R 1 9 5 4
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1411
W l r L r l r,*
IN
,ared SpectrumL of Water-Solub,le Glyoiile Deposited on a Heated So
