A pH indicator, Thymolphthalein, is used to keep track of the capacity of the alkaline
solution to retain CO
2
. Since a high concentration of a strong base is used, the initial
pH is 14. When CO
2
is added, NaOH is consumed and the pH decreases. This pH
indicator changes from blue to colorless around pH 9 (Figure 7). In this pH, the capacity
of NaOH to remove the CO
2
is reduced, indicating that the solution needs to be
changed.
Figure 7. Structure of Thymolphthalein depending on the pH.
NOTE: For most applications it is not necessary to submerge the tubing inside the
alkaline solution to remove CO
2
.
3) BPC Core AMPTS Unit (Unit C): Here the gas is recorded and processed. The BPC Core
AMPTS Unit consists of 18 or 9 flow cell units for simultaneous gas volume detection
from 18 or 9 independently operating reactors (Figure 8). Unit C comes with an OLED
screen which will display various information, including IP address of the instrument,
version of the software, current environmental parameters (temperature and
pressure), and alignment indicator. The information can be accessed through two
physical buttons located below the screen. The detection unit is equipped with an
USB port for software upgrades and possible new applications and a power button.
Figure 8. (A) Gas volume measuring device for AMPTS III and (B) AMPTS III Light.
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