GAS-PARTITION CHROMATOGRAPHY 319 Figure 7.--Gas chromatography of octyl Figure &--Gas chromatography of methyl, (Cs) aldehyde plus 1% heptyl (C0 aide- ethyl and isopropyl benzoates 190øC. hyde. TABLE I--QuANTITATIVE ANALYSIS or MIXTURE or STRAIGHT-CHAIN ALDEHYDES, C7: , C8, C9 AND C10 X Found, % Calculated, % C7 23.3 4- 0.45 25 Cs 28.2 4- 0.4 25 Co 24.4 4- 0.25 25 C•0 24.1 4- 0.15 25 half its height. Using this method, results (Table I) accurate to within a few per cent for each aldehyde were obtained. However, the reproduci- bility of the method is better than this it should be possible to get at least 1 per cent accuracy on this kind of a mixture by use of calibration chroma- tograms. Figure 8.--Gas chromatography of 1:1:1 mixture Figure 9.--Gas chromatography of of C7, Cs, Co and C•0 aldehydes. heptyl (C7) aidehyde.

320 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 10.--Gas chromatography of nonyl Figure 11.--Gas chromatography of decy! (Co) aidehyde. (C,0) aidehyde. TABLE II--QuANTITATIVE ANALYSIS OF MIXTURES OF •IETHYL, ETHYL AND ISOPROPYL BENZOATES Calculated, Calculated, Calculated, Found, % % Found, % % Found, % Methyl 32.6 q- 0.5 33.3 49.7 4- 0.7 50 25.1 4- 0.4 25 Ethyl 34.0 4- 0.9 33.3 25.7 q- 0.3 25 26.1 4- 0.4 25 Isopropyl 33.44-0.4 33.3 24.7 q- 0.45 25 48.7 q- C.1 50 The fact that the results in Table I were not as accurate as expected was suspicious. It was not reasonable to expect the analysis for the Cs to be so much higher than those for C7, Co and C•0 aldehydes when all four com- pounds were presumably present in the same amounts. It was suspected that the Cs was the purest of the aldehydes used in the mixture, and, there- fore, that the actual Cs content should be slightly higher than any of the others. Figure 9 shows a purity determination of the C7 aidehyde. The im- purity indicated is not, as one might suspect, the Cs octyl aldehyde since the retention time is not quite right. The point is that the C7 aldehyde was impure and, therefore, the low analytical figure for this aldehyde is reasonable. The same thing applied to the Co aldehyde (Fig. 10), which has sonhe Cs impurity. This would decrease the analysis for Co and increase it for Cs. Finally, in Fig. 11, the C•o aldehyde can be seen to be a complex Figure 12.--Gas chromatography 2:1:1 mixture of methyl, ethyl and isopropyl benzoates. Figure 13.--Gas chromatography of 1:1:2 mix- ture of methyl, ethyl and isopropyl benzoates.