Bimetallic Pd-Cu/Cu20 colloids are prepared by the thermal decomposition of their acetates dissolved in methyl isobutyl ketone and bromobenzene. In methyl isobutyl ketone, the average diameter of Pd-Cu20 colloids decreases from about 130 to 50 nm with an increase of molar fraction of palladium acetate, while in bromobenzene the size of Pd-Cu colloids increases from about 8 to 15 nm. The composition of Pd-Cu or Pd-Cu20 colloids is almost the same as that of the feed ratio of their acetates. The dispersion stability of these colloids is further addressed by measuring their f potentials.

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SummarySurface and micellar properties of a homologous series of Octaethylene glycol-n-alkyl ethers (C,~Es; n = 9 to 15) have been studied in aqueous solutions by the surface tension measurements. The effects of the alkyl chain length comprising even and carbon numbers have been examined in order to evaluate the surface free energy A G A_ w and the standard free energy AG~ for the micellization obtained from their surface tension data. The areas per molecule and the equilibrium surface tension values at the CMC decreased with an increasing carbon number and they showed zigzag curves by the difference in even and odd carbon numbers.These findings may be attributed to the differences in the molecular orientation between the molecules with even carbon number and ones with odd carbon number on the air-water interface at CMC. A GA_w values decreased linearly with an increasing alkyl chain length but did not show a zigzag line by the differences in even and odd carbon numbers. This suggests that the molecular orientation is not influenced by the difference between their even and odd carbon numbers in the alkyl chain on the surface of the very diluted solution, and their molecules form some stable adsorbed films with an increase of the alkyl chain length. A division of A GA_ w into the contribution made both by the hydrophilic group AG~_w (-W) and by the hydrophobic group A GA-w ( -CH2 -) was attempted as follows; A GA-w (-CH2-) = -0.80 kcal/mol and AGa_w(-W) = + 0A5 kcat/mol. The free energy changes AG m of micellization were discussed on the basis of the CMC data obtained from the surface tension measurements by treating the formation of micelles as analogous to phase separation, and the contribution from the each moieties in the molecule were calculated as follows; AG m (-CH2-) =-0.68 kcal/mol and AGm(-W) = + 1.54 kcal/mol. The difference between AG~_w and AG,~ is discussed using their data. Key wordsNonionic surfactants with even and odd carton atoms, contribution of two moieties.