Figure 1
pH Scale
a. The pH scale on the meter (figure 1) ranges from 0 to 14. The center of the scale is a pH of
7 and represents distilled water, which is chemically pure water. It is neither acid nor alkaline.
b. Acids are found in the range from 7 to 0 on the pH meter. The closer to 0 the pH reads,
the stronger the acid content of the solution being measured.
c. Alkalines are found in the range from 7 to 14 on the pH meter. The closer to 14 the pH
reads the stronger the alkaline content of the solution that is being measured.
d. In photographic processing, you are concerned primarily with two solutions -- the developer
and the fixer.
NOTE:
THERE ARE, OF COURSE, OTHER SOLUTIONS UTILIZED IN
PHOTOGRAPHIC PROCESSING AND EACH IS DESIGNED TO FUNCTION
WITHIN A SPECIFIC pH RANGE. FOR NOW, WE WILL JUST TALK
ABOUT THE DEVELOPER AND FIXER IN RELATION TO pH.
e. Developer solutions are alkaline; therefore, the pH readings would be between 7 and 14. (See
figure 7).
f. Fixer solutions are acid, and read between 7 and 0 on the pH meter.
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