EMULSION STABILITY 17 3 external phase. A special reduction in droplet size is not observed when the emulsifier concentration becomes more than 5% by weight. In addition, an emulsifier concentra- tion of about 5 % by weight is out of the zone of the dramatic creaming reduction. Based on all these, it can be proposed that polysorbate 80 be used at a concentration of 5 % by weight. ACKNOWLEDGMENTS The authors wish to express their thanks to the state Scholarship Foundation of Greece for the scholarship provided to C. A. Ayannides. REFERENCES (1) F. Liu and D. Liu, Long circulation emulsions (oil-in-water) as carriers for lipophilic drugs, Pharm. Res., 12, 1060-1064 (1995). (2) T. Takino, K. Konishi, Y. Takakura, and M. Hashida, Long circulating emulsion carrier systems for highly lipophilic drugs, Biol. Pharm. 17, 121-125 (1994). (3) B. Idson, "Pharmaceutical Emulsions," in PharmaceuticalDosage Forms: Disperse Systems, H. A. Liberman, M. M. Rieger, and G. S. Banker, Eds. (Marcel Dekker, New York, Basel, 1988), Vol. 1, pp. 236-240. (4) A. T. Florence and D. Artwood, "Emulsions," in Physicochemical Principles of Pharmacy, 3rd ed., A. T. Florence and D. Artwood, Eds. (Macmillan, London, 1998), pp. 264-266. (5) P. Prinderre, Ph. Piccerelle, E. Cauture, G. Kalantzis, J.P. Reynier, and J. Joachim, Formulation and evaluation of o/w emulsions using experimental design, Int. J. Pharm., 163, 73-79 (1998). (6) G. Ktistis and N. Iconomou-Petrovic, The influence of the concentration and HLB value of the emulsifying agents on the stability of emulsions, Pharm. Ddtion, 7, 1-9 (1981). (7) R. P. Gullapalli and B. B. Sheth, Effect of methylcellulose on the stability of oil-in-water emulsions, Int. •. Pharm., 140, 97-109 (1996). (8) E. Shotton and S.S. Davis, The use of the Coulter counter for the particle size analysis of some emulsion systems, J. Pharm. PharmacoL, 20, 430•438 (1968). (9) F. Kiekens, A. Vermeire, N. Samyn, J. Demeester, and J. P. Remon, Optimization of electrical conductance measurements for the quantification and prediction of phase separation in o/w emulsions containing hydroxypropylmethylcelluloses as emulsifying agents, Int. •. Pharm., 146, 239-245 (1997). (10) A. Martin, P. Bustamante, and A. H. C. Chun, "Micromeritics," in Physical Pharmacy, 4th ed., A. Martin, P. Bustamante, and A. H. C. Chun, Eds. (Lea and Febiger, Philadelphia, London, 1993), pp. 425•426. (11) C.A. Ayannides and G. Ktistis, A theological study on microemulsion gels of isopropyl myristate, polysorbate 80, glycerol, and water, J. Cosmet. Sci., 50, 1-7 (1999). (12) C. Valenta, E. Nowack, and A. Bernkop-Schnurch, Deoxycholate-hydrogels: Novel drug carrier sys- tems for topical use, Int. •. Pharm., 185, 103-111 (1999). (13) T. F. Tadros and B. Vincent, "Emulsion Stability," in Encyclopedia of Emulsion Technology, P. Bether, Eds. (Mercel Dekker, New York, Basel, 1983), p. 147.

j. Cosmet. Sci., 53, 175-184 (May/June 2002) Investioation of jewelry powders radiatino far-infrared rays and the biolooical effects on human skin B. H. YOO, C. M. PARK, T. J. OH, S. H. HAN, H. H. KANG, and I. S. CHANG, Skin Research Institute, Pacific Corp. / R&D Center, 314-1, Bora-ri Kiheung-eup, Yongin-si, Kyounggi-do, Korea 449-900. Accepted for publication January 31, 2002. Synopsis Far-infrared rays have certain kinds of effects on the human body, especially on skin, blood circulation, and skin cell vitalizing. Some jewelry powders radiate far-infrared rays. Jade has powerful far-infrared ray radiation, and tourmaline has pyroelectric and piezoelectric properties and radiated far-infrared rays. The jewelry powders (fine powdered jade and tourmaline powders) were screened by far-infrared rays for radiation properties and tested for the effects of far-infrared rays on the human skin by temperature observation using an infrared thermal analyzer. INTRODUCTION In recent years, jewelry powders have been applied in cosmetic formulations. Tourmaline powder has especially been a representative example, and crystalline jewelry has been used for the purpose of crystal therapy in Western countries. The main concept of this therapy has been related to oriental "ki" and "chakra," which refers to a flow of energy, and to wave energy, which has been researched for the new alternative therapy, wave therapy. Crystal therapy and wave therapy have the same concept as wave energy. Wave energy has very wide regions of wavelengths, but the most important regions are from 4 to 20 micrometers. These regions of wavelength are usually referred to as "far-infrared rays" or "biologically beneficial rays." In this study, the wavelength of far-infrared rays is in the region of 4 to 20 micrometers. Far-infrared rays have been applied in the cure of dermatologic diseases (1) such as psoriasis (2) and atopic dermatitis (3). They also have effects on living organisms and have growth-promoting effects in growing rats, sleep- modulatory effects in freely behaving rats and insomniac patients, and blood circulation- enhancing effects in human skin (4), especially in percutaneous skin blood circulation (5-7). Effects on the skin and perspiration have also been investigated (8,9). In addition, far-infrared rays affect the whole human body (10) and growth inhibition of mammary Address all correspondence to L. S. Chang. 175