Peak number plot odors

Peak frequencies of far infrared absorption spectra are plotted as dots along a linear scale. If the compounds have an odor in common or are specific attractants for a particular species of insect, the dots cluster at some places and avoid others. The number of dots in each 7-cm interval are counted and plotted to give the peak number plot. Lines drawn to standard deviations from the expected mean enable statistically significant favorable and adverse frequencies to be identified. 

Peak Number Plots for groups of compounds judged by expert human observers to have a fair degree of odorous similarity are shown in Figures 3, 4, and 5. Figure 5 includes the Plot for fifteen compounds whose odors are not related. These were compounds selected in 1966 by a Committee headed by Dr. L. M. Beidler as standard odor stimuli recommended for use in olfactory research (10). Their names and descriptions are shown in Table III. It is noticeable that in the absence of a common odor there is very little tendency to deviate from the expected mean frequency. 

Figure 4. Peak number plots for the green, rose, and orange blossom odors...

Figure 5. Peak number plots for the musty and sweaty odors, and for 15 standard odorants which represent a variety of unrelated odors, thereby showing at most only one marginally significant deviation from the number of peaks to be expected in any randomly selected group of unrelated...

The many qualifications made by expert "noses" were referred to above as constituting an obstacle to finding Peak Number Plots for particular odors. However, once a few such Plots have been developed it then becomes possible to take a fresh look at the comments and qualifications and begin to trace their origins in the respective molecular species. 

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