Gustation

Gustation refers simply to the sense of taste. Recent work by our group addresses, in particular, the sense of taste of saltiness. Our emphasis in studying the senses is on the relationship between the intensity of our sensation and the property of uncertainty (please refer, for example, to Auditory Research above). In chemistry, the property of uncertainty is measured by the entropy or disorder of the molecules under study. So our study of saltiness concerned the relationship between the intensity of saltiness and the entropy of the salty solution.

Fundamental considerations of the problem led us to understand that the saltiness of the strong salts of chlorides such as sodium chloride, lithium chloride, potassium and ammonium chloride, were related to the standard molar entropy of the salts (a value that can be found easily in a book of physical tables) by means of a simple, straight-line relationship, as shown in the figure below.

The slope of the line of saltiness should, in theory, permit us to calculate the gas constant, one of the constants of physics. The value of the gas constant, obtained by this sensory method, was found to be equal to 9.79 (joule.mole^-1.deg^-1). The accepted value for this constant is 8.31 (joule.mole^-1.deg^-1), which suggests that we are on the right track. It is actually quite exciting that we can estimate a constant of nature from a study of the human senses.

The important part of this study is, however, the relationship between sensation and uncertainty. An earlier study of this relationship can be found at the Biopsychology link, http://www.biopsychology.org/norwich/n1984/norwich1984.htm, courtesy of Dr. Esteban Barrull of the University of Barcelona.