Document 714pxgYB2478KL5M7K9jN06Jg

waiter c. me crone associates, inc. CONSULTING. ULTRAMICROANALYSIS MICROSCOPY SMALL PARTICLE PROBLEMS SOLID-STATE CHEMISTRY 31 May 1978 Dr. Julie C. Yang W. R. Grace & Company 62 Whittemore Avenue Canbridge, Massachusetts 02140 06151037 Dear Dr. Yang; Thank you for your letter of 15 May, and may I apologize for the ambiguities in ny reports of 5 April and 3 May. The portion of the sample which we examined is equivalent to the respirable fraction and represents about 17. of the bulk material. In that fraction we detected about 1 -27. chrysotile. In cur experience, our preparation method tends to concentrate the fibers in this equivalent respirable fraction, thus if all the fiber is in this fraction it would represent about 1 part in 10,000 of the total sample. If, however, a substantial portion of the chrysotile remained in the non-respirable fraction the level would of course be higher. This situation does exist to some extent in these sanples because of the intergrowth with the vermiculite. The extent to which this chrysotile might be liberated, however, can only be a matter for speculation. I trust this letter clarifies ny previous reports. Sincerely, GRG:fe ref: 6877 jero SOUTH MICHIGAN AVEsuE Chicago lU'NOlS 6:fit 3'7 S-l.-TiCC CABLE CHeMICSONE