DETERMINATION OF INORGANIC CARBON IN BLACK LIQUORS
PRINCIPLES OF OPERATION
Black liquor samples are acidified with acid to release CO2. Carbon dioxide-free air sweeps the evolved CO2 from the heated reaction chamber through an air cooled condenser, scrubbers and into the CO2 Coulometer where it is measured by automatic, coulometric titration.
- Assemble the apparatus as described in the Instruction Manual with the following addition:
Install the auxiliary scrubber between the sample column exit and the fritted sample (silver) scrubber Fill the auxiliary scrubber and the sample (silver) scrubber with a silver nitrate (AgNO3) or silver sulphate (AgSO4) solution.
- Determine the blank and run a standard to confirm proper operation of the system.
- Charge the sample tube with a known weight of the black liquor sample. The sample size should be selected to contain 1-3 mg of carbon.
- Attach the sample tube to the apparatus. Allow approximately one (1) minute for the system to purge itself of CO2.
- Move the sample tube into position over the heater, pump acid into the reaction chamber, and start the coulometer.
- When all the CO2 is evolved and titrated, the CM5017 automatically detects the endpoint, ends the analysis and prints the result to the printer and/or diskette. *
(*) – Endpoint determination and result calculations are performed automatically based on user selectable settings entered into the CM5017 CO2 Coulometer.
When samples contain over 1 mg C, the titration accuracy is +/-0.1% relative. Overall accuracy is typically +/-0.3% relative. When sample availability or volume limits the amount of CO2 evolved to small amounts, the accuracy is generally better than 1 ug C.
Analysis times are typically 5 – 7 minutes. Poor miscibility of the sample with the acid can extend the analysis time. A 50/50 mixture of kerosene and iso-propanol can be added to the sample to improve miscibility.