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Enriched isotopes of sulfur are becoming attractive for use as tracers in a variety of environmental and scientific experiments. Many stages of separation are needed, especially for 33S and 36S, which exist in low natural abundances. Small amounts of highly enriched sulfur isotopes can be provided by means of electromagnetic separation in the calutrons. However, the cost is prohibitively high for enrichment of large amounts needed by many experiments. Thus, a two-stage process is planned to obtain large amounts using gas centrifuges for preenrichment, followed by final enrichment in the calutrons.Sulfur hexafluoride is the most efficient form for processing sulfur in the centrifuges; however, SF6 is unacceptable as feed to the calutrons because it has excellent insulating properties for the high-voltage apparatus used to ionize the feed. An efficient process is needed to convert the preenriched sulfur isotopes from SF6 to a suitable form for calutron feed.Development of a conversion process is difficult because of the relatively high stability of SF6. Reiner and Simmons (1) have successfully converted SF6 to SO2 in pilot studies using a propane/oxygen flame reactor. However, H2S is a more desirable intermediate for producing metal sulfides or sulfur halides. Thus, experiments have been made using direct hydrogenation at temperatures of >900°C. Conversion to cadmium sulfide has been accomplished by scrubbing the H2S product gas with 5% CdCl2, achieving product yields of >90%. A developmental program to convert SF6 to CdS, or another more efficient form, is being carried out. Optimum conditions for the conversion are being determined, and the products are being evaluated in calutron test runs.