644 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table V Esters of Isostearic Acid CHa CHaCH-(CH2)•4COOH = 73%• isoCi6 7%• Cørmnercial n-C•6/C•a 20%]Isostearic Acid (Mol Wt 280) Approx Carbons on Viscosity Mol Wt Alcohol (Lotion)(cps) Branching Isopropyl isostearate 327 3 5800 9.4 Glyceryl monoisostearate 336 3 2348 4.5 Isodecyl isostearate 420 10 2544 7.1 n-Decyl isostearate 420 10 2360 3.5 PEG 600 monoisostearate 862 26-4- 118 1.8 Initial Slip (Scale 1-5) End Feel (Scale 4-20) PEG 600 3.5 Glyceryl 11.1 n-Decyl 3.5 PEG 600 13.5 Glyceryl 4.3 n-Decyl 16.5 Isopropyl 4.5 Isopropyl 16.8 Isodecyl 5.0 Isodecyl 17.8 Table VI Esters of Linoleic Acid CHa(CH,,)4CH:CHCH2CH:CH(CH•)7COOH C•a Acid (Mol Wt 261) Approx Carbons on Mol Wt Alcohol Viscosity (Lotion)(cps) Branching Isopropyl linoleate Propylene glycol linoleate Decyl linoleate Hexadecyl linoleate PEG 400 linoleate PEG 4000 linoleate Initial Slip (Scale 1-5) Isopropyl 3.0 Decyl 3.0 Propylene glycol 3.5 PEG 4000 3.5 Hexadecyl 3.5 PEG 400 4.5 303 3 319 3 401 10 485 16 643 174- 4243 1804- 1144 4.9 5450 ... 7900 ... 9900 17.6 277 207 End Feel (Scale 4-20) PEG 4000 8.0 Propylene glycol 11.0 PEG 400 12.0 Hexadecyl 12.5 Isopropyl 13.0 Decyl 14.5 to reduce End Feel scores, and therefore usefulness as cosmetic emollients. On the other hand, since oleic acid esters performed better than stearic esters, a little unsaturation is apparently good.

EMOLLIENCY AND CHEMICAl. STRUCTURE 645 Table VII Hexadecyl Alcohol and Esters o Cs/•CHCH20--CR Approx Carbons on Viscosity % Mol Wt Fatty Acid (Lotion)(cps) Branching Hexadecyl alcohol 242 0 790 35.1 Hexadecyl laurate 424 12 7100 20.1 Hexadecyl myristate 437 14 7150 19.5 Hexadecyl linoleate 485 18 5130 17.6 Hexadecyl oleate 500 18 5300 17.0 Hexadecyl stearate 508 18 2322 16.7 Initial Slip (Scale 1-5) End Feel (Scale 4-20) Laurate 3.0 Laurate 10.0 Alcohol 3.3 Linoleate 12.5 Linoleate 3.5 Oleate 13.0 Oleate 4.0 Alcohol 17.0 Stearate 4.0 Stearate 17.0 Myristate 4.3 Myristate 17.3 HEXADECYL ALCOHOL itself gives excellent End Feel, even though it produced a relatively low viscosity lotion (Table VII). Esteri- lying with oleic or linoleic acids substantially decreases performance. Esterifying with stearic or myristic acids does not affect End Feel at all, but does increase Initial Slip slightly. Esterifying with lauric acid de- creases performance. Unsaturation tended to decrease performance in this series. Three liquid (isoalcohol) ESTERS OF MYRISTIC ACID were avail- able for test, as well as one waxy one, myristyl myristate (Table VIII). On the whole, they all performed well. As expected, the three liquid isoesters gave somewhat better results than the solid normal ester. LAURIC ACID ESTERS seem to be poor emollients (Table IX). ESTERS OF ADIPIC ACID show extraordinarily good skin feel (Ta- ble X). All of these are diesters, since adipic acid is a dicarboxy acid the percentage of fatty alcohol or polyol in the molecule is therefore substan- tially higher than in monoesters. Results were so uniform in this series that it was difficult to draw any conclusions on the effect of systematically varying the structure of adipates. ESTERS OF LACTIC ACID also show uniformly excellent results, except for stearyl lactate, which performed poorly (Table XI). Isostearyl lactate shows an End Feel score of 17.5, 50% higher than that of the