Henning’s taste tetrahedron
an arrangement to represent four putative primary tastes: sweet, salty, sour, and bitter. These basic tastes are at the apices of the tetrahedron; a combination of two qualities, such as salty–bitter (e.g., the taste of potassium chloride), are along the edges,;and tastes combining three qualities, such as salty–sweet–bitter (e.g., the taste of sodium saccharin), are on the faces. The tetrahedron is hollow because Henning believed no chemical could generate all four basic tastes. [proposed in 1927 by Hans Henning]