A roasters reply. We've been vacuum roasting at 300 deg C for years. There is no need to go higer since the object is only to remove volotile organics. Our experiments show no isotopic shifts for either foraminifera or aragonitic carbonates. I suspect that 200 deg C would be sufficient. ----------------------------------------------------- Bob Fifer Benedum Stable Isotope Laboratory Brown University Geological Sciences Box 1846 Providence, RI 02912 Phone: 401-863-1698 E-mail: [log in to unmask] Fax: 401-863-2058