LANOLIN DERIVATIVES WITH DILUTE HYDROGEN PEROXIDE 365 of under 1 per cent per year at room temperature, when stored in the original shipping containers or in proper storage tanks. Contamination of hydrogen peroxide by dust, dirt and foreign material generally may cause more rapid decomposition. This hydrogen peroxide formula contains substantially nothing but hydrogen peroxide, water and a small amount of a stabilizer, sodium stannate.* Only deionized water should be used in diluting hydrogen peroxide and additional stabilizer should be added as described below. The recommended compound for dilution purposes is phenacetin (p-acetophentidine) 7. In the manufacturing of hydrogen peroxide-containing cosmetic products the materials of construction of all the processing equipment, storage con- tainers, and finished containers and liners must be examined carefully. The catalytic effect of many common materials on the decomposition of hydrogen peroxide cannot be over-emphasized. ]•XPERIMENTAL Water-Soluble Derivatives (see also Fig. 1) Ethoxylated lanolin alcohols (16 moles EO), ethoxylated lanolin alcohols (25 moles EO), ethoxylated cholesterol (24 moles EO), ethoxylated lanolin (75 moles EO), completely acetylated ethoxylated lanolin ester, partially acetylated ethoxylated lanolin ester. Test solutions containing 5 per cent of each soluble lanolin derivative and 6 per cent of H202 were prepared as follows: The prescribed quantity of deionized water was heated to 100øC and 400 mg/1 of phenacetin was added with mechanical stirring. After the phenacetin dissolved, the solution was cooled to approximately 45øC and the desired soluble lanolin derivative was added with continued stirring. This mixture was then cooled gradually with agitation to the 35øC-40øC range at which point the required amount of 35 per cent H•O2 was added. Mechanical mixing was continued until the solution temperature reached 25øC (room temperature). Care was taken to avoid water loss. The six test solutions were checked initially for pH and appearance. They were then analyzed for H•O• content. Titrations were made with 0.1 N sodium thiosulphate according to the following procedure: Analytical Procedure Acidify the samplet with 75-100 ml 25 per cent sulphuric acid and add 3 drops of N ammonium molybdate solution. Then add 15-20 ml of *U.S. Patent No. 2,872,293 iFor formulations containing approximately 1.5 per cent H•O•, use a 0.5 g-0.6 g sample. For formulations containing approximately 6 per cent H•O•, use a 0-2-0.3 g sample.

366 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS a 3 per cent potassium iodide solution (3 g KI in 100 ml water), mix well and titrate the liberated iodine with 0.1 N sodium thiosulphate to a yellow colour. Add several drops of starch solution, or approximately 0.2 g Thyodene as indicator and complete titration with 0.1 N sodium thiosulphate. to a colourless endpoint. AXNX1.7 ø/o A = ml sodium thiosulphate used for titration N: Normality of sodium thiosulphate M = Weight of sample The colour changes noted in the above procedure are subject to variation when formulations incorporating dilute H•O,• are analyzed. H•Ox Stability Tests The preparations to be tested were subjected to H20,• stability tests at 100øC for 24 hours, and at 66øC for 7 days. The 100øC test procedure is believed to have been originated in the early 1900's by the Merck Company,. Germany. Hydrogen peroxide solutions which record 100øC stability values of at least 90 per cent usually will maintain satisfactory shelf life for a minimum of 12 months during normal room temperature storage. This corre- lation is also applicable to formulations such as emulsion and cream products incorporating dilute H =0,•. The 66øC test procedure is a modification of the above, developed for determining H,•O= stability in cream or clouded formulations. Emulsified or clouded formulations containing dilute hydrogen peroxide which record stability values of 90 per cent or above, at 66øC, generally can also be ex- pected to exhibit satisfactory shelf stability for at least 12 months, under normal room temperature storage conditions. Both tests impose extremely severe conditions to greatly accelerate the collection of data suitable for valid prediction of product stability. 100øC and 66øC HxOx Stability Test Procedures Cleanliness of the test flasks is very important. These are 50 ml volumetric flasks with fused 3" to 4" necks. Prior to usage, the flasks should be immersed for a minimum of 1 hour in 10 per cent NaOH, and rinsed thoroughly with deionized water. The flasks should then be passi- vated by immersion for a minimum of 3 hours in 10 per cent HNOa, rinsed thoroughly again with deionized water, covered loosely with aluminium foil, and dried in an oven at 110øC. After analysis for initial H•O• concentration, exactly 50 ml of the formulation under test is placed in a treated volumetric flask. The un-