SMELL PRISM

A three-dimensional diagram representing six “primary” odors and their mixture.Scientists have not yet been able to pin down the physical and chemical makeup of substances that cause them to smell different from each other, but they have devised classification schemes based on the direct experience of odors and their mixtures. The most important is the system proposed by Hans Henning, a German research scientist. It is based on the assumption that all odors can be analyzed into six primary qualities: flowery (violet), fruity (lemon), spicy (cloves), resinous (pine), foul (bad fish), and burnt (tar). Henning (1924) held that if these basics are mixed in proper proportions they will produce any odor we can experience. To show this diagrammatically, he drew a prism and placed one of the sue primary qualities at each comer. The prism was conceived as hollow, to indicate that odors can be made up of as many as four elementary constituents, but never more. Theoretically, any given odor can be pinpointed on this prism according to its analysis—for example, if it is close to both fruity and spicy it will be largely a combination of these odors.Henning’s system works only moderately well. The odors of many substances that would be placed in the same portion of the prism actually do not resemble each other. Other aspects of odor perception are not in eluded in the classification. It does not take into account the fact that some substances are simultaneously tasted as well as smelled; nor does it recognize the cutaneous component in smell, the fact that substances often sting, feel warm or cool, or have an astringent effect. But the greatest objection to the prism lies in the absence of conclusive evidence that there are only six primary odors