MICROENCAPSULATION TECHNIQUES 97 The evaluation o[ capsules and capsular products is sometimes as much o[ a problem as is the making ot• a product. In the early stages, one usually employs relatively simple and rapid screening methods which hope[ully relate to the eventual real world situation. It• satis[actory progress is made, the evaluatory methods tend to become more complex until, finally, actual use conditions must be employed. This phase ot• testing may be quite time consuming and costly. Thus, the design ot• the evaluation procedures can be critical as regards the over-all progress o[ a given program. SUMMARY The potential applications ot• microencapsulation t•all into widely different areas such as the biomedical, agricultural, [ood, and pharmaceu- tical fields. SuccessJul product development requires careJul attention to many [actors both technical and economic. There are a wide variety ot• microencapsulation processes available [or use in specific problems, and no single process can be applicable to all types ot• situations. Most processes are subject to certain common problems such as agglomeration o[ capsules during wall deposition. At times it is difficult to see what the future holds for microencap- sulation. Certainly, there is a need [or additional basic and applied knowledge on the phenomena involved and, if this knowledge is [orth- coming, one might expect an upsurge in practical applications. Un- doubtedly, novel microencapsulation processes will be developed, which may also increase the scope o[ commercial products. In addition, as competence is increased in existing processes, costs should be reduced and the competitive position o[ encapsulated products improved. Al- ready, the technique has yielded some rather unique solutions to complex problems. Perhaps a concise assessment ot• the picture is one ot• cautious optimism, that is, progress, but not without hard work. (Received May 21, 1969) REFERENCES (1) Chang, T. M. S., "Semipermeable aqueous microcapsules, Trans. Am. Soc. Artificial Internal Organs, 12, 13-9 (1966). (2) Microencapsulation ups flavor of onion powder, Food Processing-Marketing, 56-7 (Sept., 1967). (3) Green, B. K., U.S. Patent Reissue 24,899 (November 29, 1960). (4) Wurster, D. E., U.S. Patent 2,648,609 (August 11, 1953). (5) Grass, G. M., and Robinson, M. J., u.s. Patent 3,237,596 (March 1, 1966).

98 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (6) Rindt, D. W., Blouin, G. M., and Getsinger, J. G., Sulfur coating on nitrogen fer- tilizer to reduce dissolution rate, J. Agr. Food Chem., 16, 773-8 (1968). (7) Soloway, S., U.S. Patent 3,137,131 (June 16, 1964). (8) Reyes, Z., U.S. Patent 3,173,878 (March 16, 1965). (9) Chang, T. M. S., Macintosh, F. C., and Mason, S. G., Semipermeable aqueous micro- capsules I, Can. J. Physiol. Pharmacol, 44, 115-28 (1966). (10) Massoth, F. E., Hensel, W. E., Jr., and Harlowe, W. W., Jr., Basic studies of the encapsulation process, Ind. Eng. Chem., Process Design Develop., 4, 6-13 (1965). (11) Flinn, J. E., and Nack, H., Advances in microencapsulation techniques, Battelle Tech. Rev., 16, 2-8 (Feb., 1967). (12) Sachsel, G. F., and Nack, H., U.S. Patent 3,202,533 (August 24, 1965). (13) Nack, H., U.S. Patent 3,036,338 (May 29, 1962). (14) Evans, R. B., and Herbst, W., U.S. Patent 3,159,589 (December 1, 1964). (15) Herbig, J. A., and Hanny, J. F., U.S. Patent 3,161,602 (December 15, 1964). (16) Flinn, J. E., and Nack, H., What is happening in microencapsulation, Chem. Eng., 74, 171-8 (Dec. 4, 1967). (17) Balassa, L. L., and Brody, J., Microencapsulation the Balchem way, Food Eng., 40, 88-91 (Nov., 1968).