WIDE RANGE pH INDICATOR SOLUTION
POISON. Contains methanol. Ingestion causes nausea, intoxication and central nervous system
depression and may cause blindness and death. Vapors harmful. Flammable. Do not ingest or
allow contact with skin or eyes. Do not breathe vapors. In case of contact, flush skin and eyes
with plenty of water. In case of ingestion, induce vomiting by giving salt in warm water. In case
of inhalation remove victim from exposure, treat for ingestion if symptoms appear. Call medic in
all cases. In case of fire, user smothering foam. Water may be ineffective.
The amount of pH indicator added is critical to the accuracy and should be measured as carefully
The strength of the indicator solution should be checked occasionally in the
range normally being tested.
Use the 1.0 ml pipet(5, fig. 1-1) and pipet filler(27) to transfer 1.0 ml of wide range pH indicator
solution(14) to only one of sample cells(7, fig. 2-5). Measure carefully. Swirl to mix. This is the test
Note the color of the test sample after the indicator solution has been added.
Remove the blank sample cell from the spectrophotometer. Place the test sample (the one treated with
indicator solution) into the spectrophotometer cell holder(5).
Use the two bottom scales(2, fig. 2-15)
marked 520 nm. In order for a reading to
be valid, two things must both be true.
First, the color written on meter card scale
where the needle intersects it must match
the color of the solution. Second, the
needle must intersect the scale between
the largest and smallest pH values
marked on the scale. If both conditions
are true for one of the two bottom
scales(2), the pH is the value indicated on
that scale. Otherwise, go to the next step.
Remove test sample from spectrophotometer.
Then, place the blank cell (containing
untreated test sample water) in the
spectrophotometer cell holder(5, fig. 2-5).
Adjust the wavelength dial(8) to 615 nm. Turn
the LIGHT CONTROL knob(l0) until the meter
scale(14) needle rests at the far right of its
Figure 2-15. Reading Wide Range pH Meter Scale Card.
Remove the blank sample cell and replace the test-sample cell. Read the pH value from the upper
scale(1, fig.2-15) marked 615 nm.
Interpretation of Results:
Pure water is neutral and has a pH of 7. Values of pH from 0 to 7 indicate that the water is acidic. The lower the
value the more acidic. Values of pH from over 7 to 14 (the maximum) indicate that the water is alkaline.
Refer to para 2.6.2 for shut down of the Spectrophotometer.
FOR EXAMPLE, WITH ABOVE READING:
IF SOLUTION IS ORANGE, READ BOTTOM SCALE.
IF SOLUTION IS BLUE, READ MIDDLE SCALE,
IF SOLUTION IS GREEN, ADJUST WAVELENGTH
AND READ TOP SCALE.