The linearity of the log plot of adjusted retention times versus carbon number

The linearity of the log (adjusted retention time of normal alkanes) vs. C no. is of interest because of the possibility of calcg. retention indexes by logarithmic interpolation over a wider range of C atoms than as defined by Kovats who considered the adjusted retention times of 2 neighboring (even) normal alkanes. Although by some authors this log plot is considered to have a certain curvature, at least in a part of the plot, it appears that no curvature exists at all. One of the reasons that curvature has been found is due to the general assumption in gas chromatog. that the adjusted retention time of CH4 equals zero. This induces an error which is responsible for the observed curvature in the initial region of the log plot. There is a way to get around this error, viz. by calcg. the column dead vol. point from three \"standard\" normal alkane retention times. On this basis, retention indexes of other normal alkanes were calcd. and appeared to be multiples of 100 within a small nonsystematic exptl. error. An Algol 60 program as used for the calcn. of the retention indexes is added. The use of a standard program is almost imperative in this sort of calcns. and will add to a more accurate standardization of retention index detns. as carried out in different laboratories. [on SciFinder (R)]