284 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS oc t I•1• ), I • I I I • I •'•'•1= AL -- WA IP oo I 250 300 540 WAVE LENGTH (rn•) Figure 2.--Ultraviolet absorption spec- tra ooe glyceryl p-arnino benzoate in vari- ous solvents. It should be noted that the mineral oil curve possesses a shoulder indicat- ing more than one maxima. This increase in fine structure in the absorp- tion curve results from the increased polarizability of the valence electrons when the compound is dissolved in a nonpolar media. Figure 2 presents the data on glyceryl mono-p-amino benzoate (Escalol 106). Kreps (11) recently discussed this compound as well as the newer Escalol 206 (ethyl-p-glycosylimido benzoate). The substitution of agly- ceryl group for an ethyl group tends to make little or no significant changes in the U.V. absorption spectra, when compared on an equimolar basis. However, since Escalol 106 has a molecular weight of 211 versus 165, when compared on a unit weight basis, the spectra of Escalol 106 are reduced ap- J •o5 • • o4 OH • SALOL O o3 co • 0.1 •50 300 •50 •AVE LENGTH •m•

EFFECTS OF CHARACTERISTICS OF SUN SCREEN COMPOUNDS 285 proximately 23 per cent relative to the curves for benzocaine. The data published for Escalol 206 indicate that the substitution of the glucosy[ group on the aromatic amino group increases the molar absorption charac- teristic however, the effect is nearly cancelled by the concomitant increase in molecular weight. The upper curves in Fig. 2 represent the effect of different solvent ad- ditives. The surface active agents which are able to solubilize the sun screen can markedly influence the sun screen index. Since the micelles form at such low concentration, the surfactants might be expected to cause these spectral changes at concentrations ordinarily producing negligible effect (8). Figure 3 presents the data for phenyl salicylate. Once again, the spec- trum of menthyl salicylate should be very similar on an equimolar basis. The spectra would be expected to be reduced about 23 per cent on a weight basis, relative to the curves in Fig. 3. The absorption maxima for the saUcylate compounds are shifted to the longer wavelengths. The optical densities at 308 m/• are not modified to the extent that was noted with the p-amino benzoate derivatives. However, the optical density is below 0.3 in all instances. It is probably on this basis that menthyl saUcylate is used at relatively high concentrations. It is interesting to note that the spec- tral changes which take place as the salicylates are transferred from one solvent system to another are different than those found with the p-amino benzoates. For example, Fig. 3 shows isopropyl palmirate producing a slight increase in the sun screen index for the salol, while it caused a very large decrease in the index for benzocaine of Escalol 106. A relatively large number of derivatives related to phenyl salicylate through the ortho hydroxy benzoyl group have been commercially intro- duced. One of these--2,4 dibenzoyl resorcinol (DBR)--4s shown in Fig. 4. The compound is so poorly soluble in water that we were not able'to ob- '7 •m O0 .__1 u os -- o 0.0 2•0 ß [ c c 3O0 350 380 WAVE LENGIH Figure 4.--Ultraviolet absorption spectra for 2,4-dibenzoyl resorcinol in various solvents.