Processing kodak motion picture films, module 3 analytical procedures

The Determination of Specific Gravity for Photoprocessing Solutions Using Hydrometers
ULM-0002/1
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas All All All All
INTRODUCTION
Specific gravity is the ratio of the mass of a body to the mass
of an equal volume of some other substance taken as the
standard or unit, the measurements being made at the same
temperature or, as is sometimes the case, at a stated reference
temperature. * Or stated more simply for liquids, specific
gravity is the ratio of a mass of a body to the mass of an equal
volume of water at a specified temperature. † The standard or
unit for the measurement of the specific gravity of liquids is
commonly gas-free, pure (e.g., distilled) water. Specific
gravity can be used as a measure of the total amount of
dissolved material in a solution.
“Specific gravity may be determined at any temperature
and referred to water at the same temperature or at any
desired temperature.” * The temperature of measurement
should be controlled and specified in all specific gravity
measurements because the specific gravity of a solution is
affected by temperature. Specific gravity should be stated as
follows:
Specific gravity, x/y °C
Where
x = temperature of the material being measured
y = temperature of the water
e.g., 1.050, 25.0/15.56°C
In historical analytical methods related to photographic
processing solutions, ‡ an increase of 3°C causes a decrease
of 0.001 (0.00033/°C) in the specific gravity of most
photographic processing solutions. Standards of specific
gravity for photographic processing solutions are set by
analyzing standard mixes at 25°C. The superseded version of
this method ‡ specified the determination of specific gravity
at 27°C. The temperature change to 25°C was made to be
consistent with the method currently recommended for the
measurement of pH in photographic processing solutions. § A
calculation described in Appendix A, Estimation of Specific
Gravity Conversion From One Temperature to Another,
* Taylor, john K. in Treatise on Analytical Chemistry, 1st ec.; Kolthoff,
I.M.; Elving, P.J.; Part 1, Theory and Practice, Interscience: New York,
1967; Volume 7, Chapter 81, p. 4563.
† Handbook of Chemistry and Physics, 3tth ed.; Hodgeman, Charles D., ed.
In Chief; Chemical Rubber Publishing Co.; Cleveland, OH, 1995; p. 2831.
‡ Determination of Specific Gravity of Processing Solutions; ECP-2-701,
TR Accession No. 206210L, 1974; Eastman Kodak Co., Rochester, NY.
§ Mevs, Judith M.; Jansen, Kathryn L. pH Measurement of Photographic
Processing Solutions; KPCQ-A-PR-G-191-2, TR Accession No. 266951E,
1992; Eastman Kodak Co., Rochester, NY.
estimates the effect of the temperature change from 27°C to
25°C on specific gravity.
PRECISION AND BIAS
Precision
All specific gravity readings for photographic processing
solutions are made at 25 ± 0.25°C. Historically, ‡ the
variability of measurement has been expected to fall within
±± 0.002, 95 percent of the time. ASTM Standard D891-95
states that the precision of specific gravity by hydrometer
should be determined for each chemical. For
photoprocessing control, this is not practical. ASTM gives
the following examples, however:
Repeatability (one
analyst/one day):
With-in Laboratory/
Between Days:
Bias
The bias of this test method has not been determined due to
the unavailability of suitable reference materials. However,
bias is dependent upon the calibration of the hydrometer and
the degree of control of the temperature of the hydrometer
bath.
APPARATUS
1sr (single det’n.) = 0.00020 (24 DF)
95% Conf. Est. = ± 0.0005
1s (single analyst) = 0.0016 (12 DF)
95% Conf. Est. = ± 0.005
Hydrometers
Hydrometers should meet the specifications in ASTM
Standard E 100, ** as follows:
Specific Gravity Range ASTM Number
1.000 - 1.050 111H - 62
1.050 - 1.100 112H - 62
1.100 - 1.150 113H - 62
1.150 - 1.200 114H - 62
1.200 - 1.250 115H - 62
1.250 - 1.300 116H - 62
Note: The hydrometers recommended for determining
specific gravity:
a. Are calibrated with reference to gas-free, distilled water
at 60° F (15.56°C), although measurements are made at
25°C.
b. Have subdivisions at 0.0005.
c. Have intermediate lines at 0.001.
Standard Test Methods for Specific Gravity, Apparent, of Liquid
Industrial Chemicals; American Society for Testing and Materials: ASTM
Designation D 891-95, Philadelphia, PA, August, 1995.
** Specification for ASTM Hydometers; American Society for Testing and
Materials: ASTM Designation D 100-95, Philadelphia, PA, April, 1995.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1