PI:       Margaret Leinen
of:       University of Rhode Island, Grad. School of Oceanography
    
cruise:   EqPac TTN013, Benthic survey
dataset:  Calcium Carbonate concentrations, sediment cores


Carbonate analysis methodology:

   Calcium carbonate was determined from inorganic carbon measurements made 
on a Coulometrics Inc. Model 5011 CO coulometer with a Model 5030 carbonate 
carbon apparatus.  Between 5 and 10 mg of sample were acidified with 2ml 2N 
HCl to evolve CO.  The CO gas was bubbled into a titration cell where CO 
was converted to hydroxyethylcarbonic acid which was automatically titrated 
with a coulometrically-generated base to a colorimetric endpoint.  Grams of 
carbon in the sample are calculated based on factory standardization of the 
coulometric titration.  Calcium carbonate content was calculated by assuming 
that all inorganic carbon in the sample was present as calcium carbonate, a 
reasonable assumption for these biogenic sediments which contain little or 
no dolomite.  The CO coulometer has an accuracy of 0.15 µg carbon.  The 
precision of the complete procedure is ±0.52 wt% calcium carbonate based on 
the standard deviation of a lab standard of deep sea sediment which we 
developed from the study area.  Duplicate analyses were performed on every 
tenth sample and an additional analysis was made for every pair which 
differed by more than 2 wt%.