244 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS gory--both surface active and non-surface active. Isopropyl palmirate, stearate, and ricinoleate as well as ethyl myristate, palmirate, stearate, and ricinoleate are non-surface active thinning agents. They are not as thin as the isopropyl myristate and therefore can be used in larger propor- tions. The surface active materials that can be utilized are the monopro- pylene glycol esters of lauric, myristic, and palmitic acids. They are more viscous than the corresponding alcohol esters and can be used in even greater proportions. They are poor solvents for bromo acids but do aid in its staining action. Any solvent action is invariably due to the presence of free glycol or soap. Propylene glycol monoricinoleate, however, is a good solvent for bromo. It is a mutual solvent or coupling agent for glycols, polyethylene glycols, and castor oil, helping to prevent separation and bleeding. Castor oil being the predominant ingredient of most lipsticks, we deemed it advisable to fully explore its derivatives. Castor oil is the triglyceride of ricinoleic acid (87 per cent), oleic acid (7 per cent), and small amounts of other fatty acids. For the purpose of this paper, the term ricinoleic acid refers to the purified fatty acids derived from refined castor oil. The cost of using a fatty acid freed from oleic acid and the other minor constituents would be prohibitive. The structure of ricinoleic acid is H H HHHHH HH HHH H H HH H O H--C--C--C--C--C--C--C--C--C----C--C--C--C--C--C--C--C--C--OH H H H H H H H H H H H H H H OH It differs from oleic acid in the presence of the hydroxyl group, which gives castor oil its high viscosity and solvency. This hydroxyl group also gives ricinoleic acid a high degree of reactivity. The acid on standing will cross esterify to form polymers. HHH H H H H HH H HH H H H HH O H--C--C--C--C--C--C--C--C--C----C--C--C--C--C--C--C--C--C--OH H I HH H H H H H H H H H H H H H H H 0 H H H H H H H H H H H H H H • x

LIPSTICKS--FORMULATION, MANUFACTURE, AND ANALYSIS 245 This is indicated by a rather rapid decrease in its acid number. In prep- aration of esters this reaction goes on to a considerable degree as a side reaction. The hydroxyl group does oxidize to form heptaldehyde. Even traces of heptaldehyde are sufficient to make the product unusable for lip- sticks. Quite often ricinoleates have not been fully explored because of these impurities. We use an indirect method to form the ricinoleates to avoid cross esterification. Care in selection of the catalyst and operating conditions avoids the formation of aldehydes and other odoriferous by- products. The lower aliphatic esters are made by alcoholysis of the glyc- eride. The other esters are then made by replacement of the lower alkyl radical with the desired alcohol. castor oil q- methanol -• methyl ricinoleate q- glycerin methyl ricinoleate q- cetyl alcohol -• cetyl ricinoleate q- methanol We have prepared a number of ricinoleate esters using these methods. The ethyl and isopropyl as well as the propylene glycol monoester have been mentioned previously. Cetyl and stearyl ricinoleate are liquids with melting points of 20 and 25øC. They are somewhat less viscous than castor oil. They are completely compatible with castor oil and can be used as a substantial replacement of it. The ricinoleates of lanolin alcohols and lanolin sterols are viscous products with exceptionaI emolliency. We are also making the corresponding oleates. The properties are somewhat the same for the entire series with the exception of having less body and being poorer solvents for bromo acid. The term solvents has been used several times. There are materials that are excellent solvents for bromo acid but are of limited value as they do not allow the dye to stain the skin. Polyethylene glycol ether of lauryl alcohol is a representative case. Where reference is made to a solvent, we mean one that not only dissolves the bromo acid but assists it in staining the skin. The solvents used in the high stain lipsticks fall into two groups: the free glycols or polyglycol esters and fatty acid esters of the polyglycol ethers. Of the glycols, propylene and butylene are most frequently used. The polyethylene glycols up to a molecular weight of 1000 are effective. Consideration must be given to the hygroscopic effect of these materials. Due to the anhydrous nature of a lipstick, moisture is drawn from the lips in order to establish a hygroscopic equilibrium, where these materials are used. This can result in dry, parched lips. We know of no miracle ingre- dient, with one exception, which will offset this hygroscopic effect. This ingredient is water, which is incompatible with the general type of lipstick. As the molecular weight increases, the hygroscopic effect decreases but so does the staining power of their solutions. The polyethylene glycol mono- esters of lauric, palmitic, stearic, oleic, and ricinoleic acids are good solvents. There is a tendency for the longer polyglycol chain esters to act as emulsi-