For many years scientists have tried to correlate the viscosity of pure liquids with their other physical and chemical properties. A relation between viscosity and chemical composition was observed first by Pribřam and Handl. Thorpe and Rodger attempted to assign a value to each atom in 1893. It was shown by Bingham and Harrison that fluidities rather than viscosities are additive, and they devised atomic temperature constants of fluidity for the single fluidity of 200 rhes. The effect of association on fluidity had not been noted heretofore, but Thorpe and Rodger assigned values to the iso‐grouping, the double bond linkage, the ring grouping, the hydroxyl oxygen, etc., which denoted the supposed effects of “constitution.” These constitutive effects were at least partly due to association. Bingham and Harrison gave a method for calculating the association and compared the values obtained with the values obtained in other ways. They found that the values to be assigned to a double bond, a ring grouping or an iso‐grouping are very small. Bingham and Darrall in a study of the isomeric octyl alcohols went so far as to assume that the constitution of chemical compounds does not affect the fluidity except in so far as it affects the association. It is a very simplifying assumption that the slight difference between the temperature required to give an unsaturated compound a certain fluidity and that required to give the corresponding saturated compound the same fluidity is due to association. The absence of two hydrogen atoms is made up for by the “condition of unsaturation.” Bingham and Fornwalt substantiated the conclusions of Bingham and Darrall and they were able to formulate the trend of association with changes in chemical composition and constitution for a number of types of compounds.