In this paper it is shown that the viscosity of the liquid normal paraffins can be accurately defined as a simple function of relative free-space except for values in the neighborhood of the freezing points of each compound. A novel method of extrapolating the specific volumes of this family of compounds to absolute zero is described which permits the calculation of reliable values of the relative free-space from density data. An expression of the same form as the author's function, but in which temperature rather than free-space is the primary variable (the so-called Andrade equation), fails to reproduce the viscosity of n-heptadecane over the same range of temperatures within the limits of the known accuracy of the measurements.

Values of the limiting specific volume v0 calculated by a trial-and-error procedure from n-alkane viscosity data using the author's free-space viscosity equation, lnη=B(v0/vf)+lnA,agree substantially with previously published values obtained by extrapolation of density data. Values of v0 for mercury, sodium, benzene, carbon tetrachloride, dichlorodifluoromethane, and water were calculated by the same trial-and-error procedure. In all cases the free-space equation gave a much better fit than the corresponding Andrade temperature equation, lnη=B/T+lnA.

It is shown that the Walther and Andrade equations, while very satisfactory for moderate ranges of temperature, are not adequate to define the dependence of the viscosity of liquid normal paraffins on temperature over extended ranges. One method of developing a viscosity-temperature relationship is presented that gives equations defining this dependence with satisfactory validity. The purpose of this paper is to show that the precise dependence of the viscosity of liquids on temperature is complicated. This is in contrast to the relatively simple relation for the precise dependence of the viscosity of liquids on free-space which will be presented in subsequent papers.

The free-space concept, previously applied to variation resulting from a change in temperature only, is here adapted to a case where both temperature and molecular weight vary. The molecular weight range of the n-paraffins illustrative of this case is limited to m=100 through m=240. Over this range of molecular weights the family of lines represented by lnη=B(ν0/νf)+lnA intersects the vertical axis at very nearly a common point. By assuming a common intercept and representing the slopes of this family of lines in terms of molecular weight, an expression defining viscosity as a function of molecular weight and free space is deduced. This expression reproduces the ``selected data'' satisfactorily over the molecular weight range mentioned. Its greater significance as a step in the development of a far more useful function will become apparent in the succeeding paper.

for six alkyltellurium compounds. These averages exclude three single occurrences: one tertiary mercaptan, one double branched alkyl selenide and one double branched alkyl diselenide.