Dear list members, I have just had a query from some one preparing soils for 15N and 13C analysis by CN analyzer/IRMS. They want to remove carbonate prior to analysis. Does the addition of HCl work, or does leave so much HCl residue that Cl becomes a problem in the combustino tube? Is there an accepted published method? I seem to recall one method using HCl vapor instead of the acid directly on the soil itself, but I cannot find the reference. Thanks in advance, Paul Brooks. Paul D. Brooks, Dept. ESPM-ES, 147 Higard Hall MC 3110, UC Berkeley, Ca. 94720-3110. phone (510)643-1748, FAX (510)643-5098.