As the temperature increased from 140" C to 2 5 P C, the cis, transand trans, cisNMID stayed fairly constant (Table 14) while the cis, cis NMID decreased and the mixture of trans, trans NMID and cis, trans, trans, cis MID increased from 26.4 O/o to 34.9 010. These results are in good agreement with those described in Table 6.
An increase of catalyst concentration from 0.4 O/o to 0.6 O/o (Table 15) did not result in any sigdkant change in the geometrical isomer composition of the Go dienoic fatty acids.
As the rate of agitation increased from 600 to 1180 rpm (Table 16), the cis, transand trans, cis NMID stayed fairly constant while the &, cis NMID increased and the mixture of trans, transNMID and cis, trans, trans, &MID decreased from 35.8 to 20.6 %.This accumulation of ck, cisdienoic fatty acid at high stirring intensity is ingood agreement with theresults of Table 5.
The results of the effect of the hydrogen pressure (Table 17) on the formation of transacids did not agree with the com-Table 17 I n j l m e oj-the h dro en pressure on thegeometricui and positional komr composition (wt &) ofthe Czz0 diemu at9 a d ofpartially hydrogenated m d m oils H, Pressure (Wa) 138 413 Fatty acid type &, &-NMID" 20.7k1.1 16.4k 1 .O + &, &-MID 53.3f 1.5 52.3k1.6 &, tram-+trans, clsMID 26.Ort1.0 31.3f1.3 &, trans-+trans, cir-NMID trans, tranr-NMID+ mean of 10 analyses with standard deviation mon effect generally observed, for example, for the monoethylenic fatty acids (Table 5). Increasing the hydrogenpressure from 138 to 413 kPa had only a minor effect but decreased the amount of ck, cis NMLD and favoured the formation of trans fatty acid. Due to the high iodine value of the starting oils, the fatty acid compositions of the partially hydrogenated menhaden oils are usually complex and require a sophisticated series of analytical methods. Many reactions are taking placesimultaneously ; hydrogenation of the polyunsaturated acids, geometrical isomerization, and migration of ethylenic bonds. From the hydrogenations effected under different conditions,it also seems that the ethylenic bonds close to the carboxyl group, especially in the cis A5, trans A 5 and trans A6 positions, are the hardest to hydrogenate.
Our studies suggest that it would be very hard to drastically modify the fatty acid composition of partially hydrogenated menhaden oils by changing the reaction parameters. Only the S , I selectivity seems to be affected by the temperature, nickel concentration, or rate of agitation. A c k n o w l e d g m e n t s This work was funded in part by a joint research grant from the US. Department of Commerce and the Zapata Haynie Corporation, Reedville, Virginia, and in part by a grant from the Natural Sciences Research and Engineering Council of Canada. We thank B. Teasdab and G. Helmel from Canada Packers who provided the facilities for the hydrogenation reactions and G. Finke from Technical University of Nova Scotia for the computer analyses.