proved a t adsorbent-saniplc ratios of 10,000 and 20,000 to 1 by using more n-heptane as a n eluent. In the Shell analyses, the perccntage of alkanes in the n-heptane eluates dccrcases continuously as the alurniii;t-sample ratios increase, and a t Iiigher ratios the aluinnia separations approach the wparation accomplished by urea adduction. I n addition to the separations of paraffins and naphthenes, molecular weight separations of n-paraffins also occur. The percentage of the individual nparaffins in the n-heptane and carbon tetrachloride eluates at various aluminasample ratios are given in Table 11. The contribution of ions produced from polycyclic naphthenes, particular11 a t loii er carbon numbers, introduces some error in the values shown. I n Table 11, the paraffins of higher molecular n eight are concentrated in the cai bon tetrachloride eluate a t all adsorbcntsample ratios, and as the alumina-sample ratios increase, the concentrations of the n-paraffins of lower molecular n eight in the carbon tetrachloride fiactions increase. The niolpcular n eight eeparation of n-paraffins is shonn by the z = f 2 plots in Figure 3. The silica gel fraction is the original sample t h a t was separated on alumina. The nheptane eluate from aluiiiina contains the n-paraffins of lou-er-molecular weight as shown by the maxinia a t lair-er carbon numbers in the z = f 2 plot ( B ) . The maxinia a t higher carbon numbers in plot C show that the carbon tetrachloride fraction contains the n-paraffins of higher niolecular n-eight CONCLUSIONS
The n-paraffins in recent marine sediment extracts haye higher concentrations of odd- than of even-carbon-number molecules. The mass spectra of the saturated hydrocarbon fractions containing these n-paraffins provide a n excrllent means of studying the separations of thr n-paraffin. and cvcloalkanes in t h r v fraction
