Lab 1 – Preparation of a Hand Cream Introduction Hand creams function to soften the skin and prevent dryness, eliminate natural waste products (usually oils) by emulsification, and cool the skin. Formulations for hand creams must also ensure spreadibility. Hand creams may also contain fragrance or medications In this laboratory exercise you will be synthesizing four hand creams. You will compare the pH, smoothness, homogeneity, and appearance of each of the hand creams. Additionally, you will ascertain the function of the ingredients utilized in the preparation of the hand cream samples. Theory Formulations for most hand creams commonly contain water for moisture and lanolin which aids the absorption of water by the skin. Lanolin has the ability to absorb 2530% of its own weight of water thereby forming a fine emulsion. Lanolin is a yellowish wax composed of esters of long chain fatty acids and long alcohol chains. Spreadibility of the hand cream is a function of mineral oil. Mineral oil consists of high molecular weight hydrocarbons. Homegeneity of the hand cream requires the inclusion in the formulation of strong emulsifying agents. Emulsifying agents ensure that nonpolar substances such as lanolin and mineral oil will uniformly disperse in the polar water medium. An emulsifying agent must have a hydrophobic portion that interacts with the nonpolar components of the hand dream and a hydrophilic portion that interacts with the water. A mixture of stearic acid and triethanolamine react to produce a salt that is a commonly utilized emulsifying agent. Textures of hand creams can be modified by the inclusion of alcohols or esters. Two common examples are 1,2-propanediol and methyl stearate. Procedure You will use the basic procedure outlined below to prepare four (4) different samples of hand cream. You will use the same procedure for each hand cream sample but the formulations for each sample of hand cream will be different. See the tables on the next page for each formulation. 1. In the fume hood while using a hot water bath, heat the polar ingredients in a 100 mL beaker for 5 minutes. Set these aside. 2. In the fume hood, while using a hot water bath, heat the nonpolar ingredients in a 50 mL beaker until all the ingredients melt. Set these aside. 3. Into the 100 mL beaker (this will contain the polar ingredients) slowly pour the molten nonpolar ingredients. Stir the mixture until you a smooth uniform paste. This will probably take about 5 minutes. 4. Use pH paper to test and record the pH of each of the hand cream samples. 5. Place a small amount of each of the hand cream samples between your fingers. Make a note of the smoothness, homogeneity and texture. Hand Cream Formulations Sample 1 Polar Ingredients Non Polar Ingredients 25 mL distilled water 1 mL (27 drops) triethanolamine 0.5 mL (20 drops) 1,2-propanediol (propylene glycol) 5 g stearic acid 0.5 g methyl stearate 4 g (spoon to marking) Lanolin 5 mL mineral oil Sample 2 Polar Ingredients Non Polar Ingredients 25 mL distilled water 1 mL (27 drops) triethanolamine 0.5 mL (20 drops) 1,2-propanediol (propylene glycol) 5 g stearic acid 0.5 g methyl stearate 4 g (spoon to marking) Lanolin Sample 3 Polar Ingredients Non Polar Ingredients 25 mL distilled water 1 mL (27 drops) triethanolamine 5 g stearic acid 4 g (spoon to marking) Lanolin 5 mL mineral oil Sample 4 Polar Ingredients Non Polar Ingredients 25 mL distilled water 0.5 mL (20 drops) 1,2-propanediol (propylene glycol) 5 g stearic acid 0.5 g methyl stearate 4 g (spoon to marking) Lanolin 5 mL mineral oil Data and Observations Prepare a data table that compares each of the hand cream samples on the basis of pH, smoothness, homogeneity and appearance Conclusion In your conclusion discuss the differences in the formulations utilized and the resultant impact on the characteristics of the hand creams that you prepared. Reasons for Error Include specific errors as appropriate.
