variations in the chemical composition.
the chemicals to dissolve properly, generally about 30
sample bottle should not be shaken, and it should be
allowed to stand for 10 minutes after the sample is
large particles to settle or turbidity (caused by
Ordinarily, determining the pH and the specific
these tests are followed up with valid sensitometric
solution. The pH of a solution is the negative
logarithm of the hydrogen ion concentration. The
electrical potential between the glass electrode of a pH
meter and the solution surrounding it indicates the
hydrogen ion concentration.
value, you must standardize the temperature.
Generally, you make pH measurements at the same
temperature that the photographic process is operated.
A change of 10°F produces a pH change of
approximately 0.10 in a processing solution at a pH of
13.0. Thus temperature control is more important at
adjust the meter consult the instruction manual or the
read several samples. Of course, the more samples
Usually, you must determine the pH value of more
than one sample. After four samples have been read,
elapse between any pH meter standardization or
Check the average value against the standard pH for
that solution. When the pH is within limits, enter the
value in the appropriate location on the certification
sheet. When the pH is not within limits, further
investigation is necessary.
actual dilution of a developer is obtained by
comparing a fresh developer to a used one. Another
application may be to compare a fresh fixing bath to
a used one. Since the silver content of a fixer
increases with use, it is logical to assume that a
experience, you will be able to establish upper- and
lower-control limits for specific gravity of the various
solutions needing such a check.
recommended by the manufacturer, because
temperature affects the specific gravity of a solution.
Specific gravity standards for black-and-white
processing solutions are set at 70°F, because many of
these solutions are used in 70°F surroundings.
simply indicate a change. So, further testing is
required. When a developer is being replenished
properly, specific gravity remains constant. If the
flow of replenisher stops, a change of specific gravity
will become evident. Replenisher flowmeters should
indicate such a problem, but a backup check of
specific gravity and pH, along with control strips, are
recommended as well.
gravity measurements of the developer are within
tolerance, this test can certainly validate the activity of
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