370 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The Stability of Hydrogen Peroxide in Emulsion Formulations containing Lanolin Derivatives In order to draw valid conclusions it was felt necessary to test the stability of hydrogen peroxide in emulsions of the type used in the cosmetic industry. Formulations utilized here are to be considered as suggested starting points which may be varied to meet individual requirements. The various lanolin derivatives employed in these formulations have been tested by the usual procedures for establishing safety, and have been found non- irritating and hypo-allergenic. Wide use over a period of many years has substantiated these findings. It is recommended, however, that completed formulations be tested to establish the safety of finished products. These emulsions were made using lesser amounts of lanolin derivatives, and higher concentrations of fatty alcohols than in the previously described water-insoluble lanolin derivative dispersed systems. They are better balanced, have higher viscosities, and, in general, are more elegant cosmet- ically. Table 3 gives the composition of the eight emulsified H20• lotions. Table 3 Emulsified H202 Lotions (See also Fig. FORMULA A V C D E F G H Oil Phase I iq. Multi-sterol Extract Sol. Multi-sterol Extract Absorption Base .. Acer. Lanolin .... Acet. Lan. Alcohols .. Lan. Alcohols Ricinoleate Cholesterol USP .. Ethox. Lan. Alc. (16 mol EO) Ethox. Cholesterol .. Cetyl Alcohol NF .. Stearyl Alcohol USP .. Mineral Oil 70 vise .. % 3'0 1'0 % % % % % % % 5-0 -- 2.0 2.0 2.0 -- -- ..... 2.0 -- ...... 2.0 -- -- -- -- -- 1.0 -- -- -- .... 1.0 -- -- 0.1 -- 4.0 4.0 4.0 4-0 4.0 4-0 3.0 2.5 -- 3.0 3.0 3-0 -- -- 2-5 3.0 -- -- -- 3.0 3-0 -- 2.9 -- -- -- 1'0 1.0 Water • Phenacetin USP .. Phase [_Water, deionized .. 0.04 72.• 1 Hydrogen Peroxide 35% .. 17.15

LANOLIN DERIVATIVES WITH DILUTE HYDROGEN PEROXIDE 371 Data on the stability of the H,,.02 in these eight emulsion formulations were then obtained in the same manner as previously described for the water-soluble derivatives. They are recorded in Table 4 along with data on consistency and emulsion stability, at room and incubator temperatures. Table 4 Stability Data on Emulsified H•O 2 Lotions Lotion Appearance (42 days)* Initial H•O• Stability Stability Stability at at Formula Consistency room temp. 43øC pH H•O• 100øC ** 66øC ** % % % A medium excellent fair 3-95 6-34 63-1 95.5 B medium .... 3.90 5.74 64-6 97.1 C medium ,, poor 3-90 5.85 72.3 98-8 D heavy ,, exc. 3-95 5.83 69.8 97.9 E heavy ,, fair 3.95 5.13 78.2 96-8 F heavy ,, exc. 3.90 5-82 73.9 95-7 G heavy .... 4'00 6.18 90.0 95-1 H medium .... 4.00 6-08 84.9 95-9 *No change in colour and no development of odour occurred. **All emulsions stratified during the 66øC and 100øC tests. They were remixed before analysis and after mixing have remained stable at room temperature. The data indicate that all eight emulsified lotions exhibit very satisfactory H•O• stability values in tests run at 66øC for 7 days. Although the 100øC test results are not satisfactory in six of the preparations, it is felt that the 66øC test values are more meaningful for emulsions. These formulations could be expected to exhibit satisfactory H•O,. stability under normal room temperature storage conditions for at least twelve months. All the formu- lations are opaque, white preparations which still demonstrate excellent room temperature emulsion stability after ageing for six weeks. No colour or odour changes took place during that time even at incubator temperatures. Incubation at 43øC brought out weaknesses in emulsion stability. Formula C, containing the highest percentage of mineral oil and the lowest amount of water-insoluble lanolin derivative, was the poorest in this respect. Consistencies varied with formula changes those containing multi-sterol extracts being the heaviest. Formula F contains lanolin alcohols ricinoleate, a product which had not previously been tested for compatibility with H•03. This formula proved to be quite satisfactory, both in emulsion, and in H•O,., stability. The preparations were checked again for emulsion stability at the end of 12 weeks of ageing at room temperature and in the in- cubator at 73øC. The results were unchanged from those reported in Table 4.