1 Antichap Lipstick and Nonbonded Clark Most, Jr.

Delta College university Center. Michigan 48710

( Interactions

1 A nonscience majors laboratory experience

This experiment not only introduces some basic con- cepts, but results in production of a very good, useahle product. Students are generally enthusiastic and highly pleased with the results.

Aotichap lipsticks have become very popular to help pre- vent chapped lips. The antichap properties of such prepa- rations presumably arise as a result of helping to maintain higher moisture content in the lip tissues by virtue of the relative impermeability of the lipstick components to mois- """chap lipstick and nonbonded interactions.

ture. A nonscience majors laboratory experiment to prepare

an antichap lipstick permits emphasis of the rule of thumh solubility relationships "like dissolves like" and "unlikes do not dissolve." For examde. the readv dissolution of the I~D- stick components in one another imphasizes the former rule of thumh concept and the water-im~ervious character of the lipstick demonstrates the latter. The experiment il- lustrates the im~ortance of nonhonded interactions, so im- portant in praEtical chemistry and everyday living hut which are so often neglected in chemistry courses, (e.g., hy- drogen bonding of protein strands and water during setting of hair; ion-dipole interactions of CaClz and water in keep- ing the dust down on side roads, etc.). The fact that the lip- stick ingredients dissolve when heated and solidify when cooled to make a solid stick is based on the non-bonded in- teractions between the various materials present. The long hvdrocarhon chains of the esters oresent are attracted to each other primarily by van der Waals forces, whereas their carhoxvl functions. containine hiehlv electroneeative - " "

atoms, create small dipoles which tend to become aligned with each other via dipole-dipole forces or may interact through hydrogen bonding with the hydroxy function of nearby alcohols. What permeability of water is permitted can be attrihuted in part to the small size of the water mol- ecule and its transient attractions with the alcohol and ester dipoles.

The concept of thixotropy can he introduced with this experiment. Thixotropy results when a multitude of min- ute intermolecular forces are readily set up hut are also quite easily disturbed. The thixotropic composition of the' lipstick is desirable since i t allows the surface of the stick to be fluid while friction of application supplies enough ener- gy to keep molecules of the stick in motion, but allows the stick to remain solidified when a t rest.

Since this experiment utilizes only N.F. or U.S.P. materi- als and requires an ultraclean laboratory, there is also an emphasis on the necessity for a pharmaceutical atmosphere and purity of ingredients.

Experimental

Before beginning work on measuring out any materials far prep- aration of the antichap lipstick, clean the entire bench top at the lab bench where you work by wiping it with a wet sponge. Neat, thoroughly scrub the area where you work as far as you can reach in any direction with a suitable cleaner or scouring powder and water; then rinse your work area twice with fresh water. Similarly clean all laboratory equipment you will need to use. Do not com- mence formulation of your lipstick until your work area has been

inspected by the lab instructor or safety chairman. As you work, confine your activities to your lab bench area. Do not remove U.S.P. or N.F. chemicals from their containers with any utensil other than that provided for each container.

Preparation of the Lipstick Tube

Cut from a sheet of aluminum foil a section 12 X 10 em. Make a 2-em fold at opposite ends of the 12 em length, and smooth the foil so that there are no wrinkles.

Place a number six eork borer at one end at right angles across the width of the folded foil and roll it tightly as shown in the fig- ure. Hold the fail in position with a strip of scotch tape. Prepare an appropriate and attractive label and affix it to the tube before re- moving the eork borer so as to prevent denting or collapsing of the tube afterwards. Cover the label with cellophane tape. Cautiously slip the borer out and insert a number three cork with the larger diameter upward, then place the same end of the aluminum tube firmly over the small end of a number four cork, and secure it with another strip of tape. Take care not to dent the tube while work- ing. The smaller cork can act as the plunger to move the lipstick upward as it becomes used, and the larger cork serves to keep the melted ingredients from running out during pouring of the lip- stick.

Formulation of the Lipstick

Ingredients: Carnauha wax 1.0 g beeswax 1.6g lanolin 0.6 g cetyl alcohol 0.6 g castor oil 6.2 g hutylp-hydraxbenzoate 5 mg DL-menthol 10 mg

A thoroughly cleaned 8 em diameter evaporating dish rinsed with acetone can be used as the dish to contain the waxes. Careful- ly weigh into the dish all the ingredients of the lipstick, except the menthol, in the indicated amounts. Heat and mix the materials on a steam bath until all materials have melted and a homogeneous solution results. To make a steam bath, use a 150-250-m1 beaker containing a boiling chip and about 50 ml of water. Rest the evapo- rating dish with its contents on the top of the beaker and boil the water using a Bunsen burner. After the mixture is melted and stirred together, put in the menthol; then immediately pour the so- lution into the mold you have prepared. A conical indentation will form at the top of the stick as a result of shrinkage; so after the stick has hardened, pour an additional amount of the molten ma- terials into the tube until the stick becomes convex at the tip. After the new addition has become solid, pass the tip briefly through a flame to impart a smooth, glossy finish. Present the lip- stick to your instructor for inspection.

194 / Journal of Chemical Education