Viscosities have been measured of thirty-seven organic liquids, with molecular weights ranging from 120 to 807, and the viscosity-temperature curves obtained are compared with those of n-paraffins. The influence of ring structures and polar groups on viscosity is discussed. Β§ 1. {ntroduction. Viscosity data of pure organic liquids with molecules of medium size are increasingly recorded in the literature. E v a n s 1), in 1938, collected the data of a n u m b e r of hydrocarbons, including 74 with 20 or more C-atoms. Since then K 1 o s, N e y m a n-P i 1 a t and P i i a t ~) have reported on hydrocarbons containing 22 C-atoms and consisting of short chains and aromatic or naphthenic ring structures. C o s b y and S u t h e r 1 a n d and later S c h i e s s 1 e r and coworkers 3) published viscosity data of a large v a r i e t y of cyclic and non-cyclic hydrocarbons, having for the greater part between 20 and 40 C-atoms.
Viscosities are also known, through the work of B i n g h a m and S t e p h e n s ~) , of J o g l e k a r and W a t s o n 5) a n d o f B r i e d et al. "), of m a n y esters with a n u m b e r of atoms comparable to that of the above mentioned hydrocarbons. A few alcohols and acids with a carbon chain of some length have a!so been investigated b y B i n g h a m e t a l . ~) 7 ) . When two medium-sized hydrocarbons or esters have the same viscosity at one temperature, t h e y m a y have quite different viscosities at another temperature. For example, large differences in slope of the viscosity-temperature curve do exist between long flexible molecules t h a t can move in parts and more compact, more rigid