Thermo Fisher Scientific C101 Colorimeter - Manual (Page 24)

Measurement: pH
C401/301/101 Colorimeter
20
Invert several
times to mix. Add 20 drops of pH Indicator
(Phenol Red)
pH
Indicator
(Phenol
Red)
9. Gently push the vial back fully into the sample well of the instrument,
whilst again aligning the ▼ mark on the vial with the ▲ mark on the
meter.
10. Wait for 1 minute and then press the READ/ENTER key within 3
minutes from when the time the Phenol Red was added to the vial.
11. The meter will flash [PH] whilst the measurement is taken. It will then
display the pH of the solution in pH units.
pH
Sample
READ
ENTER
pH