LANOLIN DERIVATIVES IN SHAMPOOS 791 fluenee of the ratio of ethylene oxide to lipophilie moiety on the orienta- tion of the additive in the bubble structure. The comparative per- formances of the shampoos containing derivatives Nos. 25 and C-24 provide an indication of the importance of the size and structure of the lipophilic portion of the molecule to surface orientation. These two lanolin derivatives contain approximately the same per cent ethylene oxide on different fractions of lanolin sterols and alcohols. In deionized water at 23 øC, derivative No. 25 is a better additive than No. C-24. If the foams are generated in moderately hard water instead of de- ionized water, the shampoos containing the soluble lanolin derivatives generally form richer, wetter foams with larger bubble size as evidenced by the increase in specific foam volume and per cent drainage. The shampoo containing derivative No. 16 again produces a more desirable foam than the one containing No. 25. However, derivative No. C-24 is a better additive than No. 25 in moderately hard water. Derivative No. 75, which contains the highest per cent ethylene oxide content, is not as desirable an additive in moderately hard water as it is in deionized water. Its extremely long ethylene oxide chain or its high molecular weight may account for its inability to complex the Ca ++ adequately. It is interesting to note that the shampoos containing the acetylated soluble lanolin derivatives Nos. 97 and 98 produce better foams in moder- ately hard water than in deionized water. This improved performance as additives in the presence of Ca + + may be attributed to their compara- tively low ethylene oxide content or to the very complex structure of their lipophilic moieties. The data suggest that the total molecular structure determines the capability of an additive to function well in moderately hard water. When the temperature is raised to 45 øC, there is a general increase in the per cent drainage. Foams generated at the elevated temperature are richer and wetter than those generated at 23 øC. Acceptable foams are produced by all the shampoos except those containing 2% of derivatives Nos. 25 and C-24, and 2% of ethoxylated stearyl alcohol. The shampoo containing 1% of derivative No. 25, however, produces foams in the ac- ceptable range, while the ethoxylated stearyl alcohol is an unsatisfactory additive at all the concentrations tested. In hot water, derivatives Nos. 16 and C-24 are again better additives than No. 25. A dramatic in- crease in per cent drainage is exhibited by the shampoos containing derivatives Nos. 75, 97, and 98 at the higher temperature. These lanolin derivatives all have very complex lipophilic structures.

792 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS In the presence of synthetic sebum at 45 øC, there is a general reduc- tion in both specific foam volume and per cent drainage, indicating a tendency toward drier foams with a smaller bubble size. In contrast to the control, the shampoos containing derivatives Nos. 16, 25, and 75 gen- erate acceptable foams while the control does not. As in the other test conditions, derivative No. 16 is a more desirable additive than No. 25. Spangler attributed good performance in the presence of sebum to emul- sifying power (7). Although all of these soluble lanolin derivatives are O/W emulsifiers, the differences in their structure and ethylene oxide content may determine the specificity of their response to the particular fatty material added. SUMMARY AND CONCLUSIONS The influence of six different water-soluble ethoxylated lanolin derivatives on the foam characteristics of a typical shampoo system was determined using relatively simple laboratory procedures. Ethoxylated stearyl alcohol was also evaluated for comparative purposes. Reproducible quantitative measurements of specific foam volume and per cent drainage after five minutes were utilized to characterize the foams. Significant differences in foam properties were detected when additive concentration or chemical constitution were the experimental variables, establishing the value of the described test procedures and measurements for evaluating shampoo additives and for determining the concentration required for optimum foam properties. On the basis of subjective evaluation of appearance and feel of more than 100 foams, a minimum specific foam volume of 13.5 ml/g and a range of 60 to 70% drainage were established as criteria for acceptable foams. Satisfactory shampoo foams must meet both these limits. All of the additives were tested at 1, 2, and 5%. In general, a signifi- cant response to changes in concentration was observed. The "opti- mum" concentration for each additive was not necessarily the same. Four test conditions representative of some probable use-environ- ments were studied: deionized water at 23 øC and at 45 øC moderately hard water (150 ppm Ca ++) at 23 øC and presence of synthetic sebum in deionized water at 45 øC. Significant differences between the perform- ance of the control shampoo and of the shampoos containing the addi- tives were noted at all test conditions. The presence of the ethoxylated lanolin derivatives generally improved foam properties, especially in moderately hard water and in the presence of sebum. The ethoxylated