Instrument: CO2 Coulometer

Instrument Short Name: CO2 coulometer
(http://vocab.nerc.ac.uk/collection/L05/current/LAB12)
Instrument Description:

A CO2 coulometer semi-automatically controls the sample handling and extraction of CO2 from seawater samples. Samples are acidified and the CO2 gas is bubbled into a titration cell where CO2 is converted to hydroxyethylcarbonic acid which is then automatically titrated with a coulometrically-generated base to a colorimetric endpoint.

PI supplied instrument name: UIC 5400
Dataset-specific description

The temperature within experimental tanks was measured every
other day with a NIST-calibrated partial-immersion organic-
filled glass thermometer (precision + 0.3%, accuracy + 0.4%).
Salinity was measured every other day with a YSI 3200 conduc-
tivity meter with a YSI 3440 cell (K 1⁄4 10) that was calibrated
with seawater standards of known salinity provided by the labora-
tory of Prof. A. Dickson of Scripps Institute of Oceanography.
Seawater pH was measured every other day with a Thermo Scien-
tific Orion 2 Star benchtop pH meter with an Orion 9156BNWP pH
probe, calibrated with 7.00 and 10.01 Orion NBS buffers traceable
to NIST standard reference material (for slope of the calibration
curve) and with seawater standards of known pH also provided
by Prof. Dickson’s laboratory (for y-intercept of the calibration
curve). Seawater DIC was measured via coulometry (UIC 5400)
and TA was measured via closed-cell potentiometric Gran titration
calibrated with certified Dickson TA/DIC standards. Measure-
ment of DIC and TA of the certified reference materials (CRMs)
were consistently within 0.3% of certified values. Differences
between the measured and certified TA and DIC values of
the CRMs were used to correct measurements of experimental
seawater solutions.