To know how to formulate and prepare vanishing cream with specific ingredients and instructions.

Steps to Solve

1. Determine total mass for 50g formula
   We need to prepare 50g of vanishing cream. The total mass is the sum of all ingredients.

2. Calculate the amount of each ingredient for 50g
   Use the proportions provided to calculate how much of each ingredient is needed:

   • Stearic acid: $ \frac{17}{100} \times 50 = 8.5 , \text{g} $
   • Potassium Hydroxide (KOH): $ \frac{0.7}{100} \times 50 = 0.35 , \text{g} $
   • Glycerin: $ \frac{5}{100} \times 50 = 2.5 , \text{g} $
   • Rose oil: $ \frac{2}{100} \times 50 = 1 , \text{g} $

3. Calculate amount of water needed
   The remaining weight needed to reach 50g is for water: $$ \text{Total weight of ingredients} = 8.5 , \text{g} + 0.35 , \text{g} + 2.5 , \text{g} + 1 , \text{g} = 12.35 , \text{g} $$ Therefore: $$ \text{Water} = 50 , \text{g} - 12.35 , \text{g} = 37.65 , \text{g} $$

4. Convert ingredients from grams to mL if necessary
   Using the densities to find the volume of glycerin and rose oil:

   • Glycerin: $$ \text{Volume}_{\text{glycerin}} = \frac{2.5 , \text{g}}{1.26 , \text{g/mL}} \approx 1.98 , \text{mL} $$
   • Rose oil: $$ \text{Volume}_{\text{rose oil}} = \frac{1 , \text{g}}{0.964 , \text{g/mL}} \approx 1.04 , \text{mL} $$

5. Prepare the vanishing cream
   Combine all the measured ingredients (in grams for solids and in mL for liquids) in the process of preparation. Ensure proper mixing until the cream reaches a uniform consistency.