Processing kodak motion picture films, module 3 analytical procedures

d. Have main (numbered) lines at 0.005.
e. Are available from most suppliers of scientific products.
Hydrometer Cylinder
The hydometer cylinder should have a capacity such that:
a. Its inside diameter is 25.4 mm (1.0 in) ≥ the outside
diameter of the hydrometer.
b. The lowest point of the hydrometer will be at least
25.4 mm (1.0 in) above the bottom of the cylinder.
Note: A 250 mL graduated cylinder is adequate for most
measurements.
Water Bath (Constant Temperature)
The water bath should be of sufficient size to allow total
immersion of the hydrometer cylinder, adjustable to 25°C,
and able to control temperature ± 0.25°C (same
requirements as the method for pH measurement § ).
PROCEDURE
1. With the clean and dry hydrometer cylinder on a level
support, fill the hydrometer cylinder with the sample
and place in a vertical position in the water bath. Avoid
the formation of bubbles in the cylinder.
2. Allow the sample to equilibrate in the water bath to a
temperature of 25 ± 0.25°C.
3. Clean and dry the hydrometer thoroughly and
carefully lower it into the sample to a level two
smallest scale divisions below that at which it will
float and then release the hydrometer.
4. Allow the sample temperature to re-equilibrate to
25 ± 0.25°C. Remove the cylinder from the water
bath.
5. After the hydrometer has come to rest and has floated
freely away from the walls of the cylinder, read the
hydrometer at eye level. Take the reading at the level
of the meniscus, where the sample surface seems to
become a straight line cutting the hydrometer scale.
See Figure 1, Meniscus.
Figure 1 Meniscus
Reading
F009_0169AC
CALCULATION OF SPECIFIC GRAVITY
No calculations are required, as the hydrometers are direct
reading and the final measurement requires no computation.
APPENDIX A
Estimation of Specific Gravity Conversion From
One Temperature to Another
If it is assumed that the change in specific gravity with
temperature is approximately 0.001 per 3°C (0.00033/°) for
all processing solutions (see the INTRODUCTION), the
specific gravity can be converted from one temperature to
another by:
specific gravity @ T 2 /y = (T 1 - T 2 )k + specific gravity @ T 1 /y
Where
T1 = original temperature, °C
T2 = second temperature, °C
k = change in specific gravity per °C (0.00033)
y = a constant (temperature of the water standard)
Example:
T1 = original temperature, 27.0°C
T2 = second temperature, 25.0°C
k = change in specific gravity per °C (0.00033)
Cylinder
Wall
MENISCUS
Solution
Hydrometer
Stem
specific gravity @ T2 /y = (27.0 - 25.0)(0.00033) + 1.020
specific gravity @ T2 /y = 0.00066 + 1.020
specific gravity @ T2 /y = 1.021
2 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03