ASTM E116-97
(Practice)Standard Practice for Photographic Photometry in Spectrochemical Analysis (Withdrawn 2002)
Standard Practice for Photographic Photometry in Spectrochemical Analysis (Withdrawn 2002)
SCOPE
1.1 This practice covers the calibration of photographic emulsions and their use in measuring spectral line intensity ratios. Several methods of external illumination are outlined. Instructions are given for using regression in a computer program for defining the emulsion calibration from preliminary curves prepared by using the two-step and two-line methods and the in-line group procedure. Correction for spectral background is discussed in some detail, and instructions are given for preparing analytical curves.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation:E116–97
Standard Practice for
Photographic Photometry in Spectrochemical Analysis
This standard is issued under the fixed designation E116; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (ϵ) indicates an editorial change since the last revision or reapproval.
1. Scope mittance, T; or optical density, D. Transmittance is the ratio of
the microphotometer reading at the darkest portion of the line
1.1 This practice covers the calibration of photographic
image to that obtained on an unexposed portion of the plate or
emulsions and their use in measuring spectral line intensity
film (the “clear-plate” reading). In practice, this ratio is often
ratios. Several methods of external illumination are outlined.
expressed as a percentage. For example, t =0.38 is equivalent
Instructions are given for using regression in a computer
to T =38. Optical density is defined as D =2−logT. The
programfordefiningtheemulsioncalibrationfrompreliminary
optical density corresponding to T =38 is D
curves prepared by using the two-step and two-line methods
=2−log(38)=2−1.580=0.420. For determining emulsion
and the line-group procedure. Correction for spectral back-
calibrations in this practice these measurements of density are
ground is discussed in some detail, and instructions are given
transformed to the Seidel density, ∆,(Note 1) defined as
for preparing analytical curves.
−D
log[(1/t)−1] or log[(100/T)−1] or log(10 −1). Conven-
1.2 This standard does not purport to address all of the
tionally, these Seidel densities have been expressed as log to
safety concerns, if any, associated with its use. It is the
the base 10. Use in computer, or electronic calculators, makes
responsibility of the user of this standard to establish appro-
it more convenient to revise these definitions on the basis of
priate safety and health practices and determine the applica-
natural logs.
bility of regulatory limitations prior to use.
NOTE 1—This function was first suggested by Baker (Ref 1). It was
2. Referenced Documents
brought to the attention of spectrochemists in a talk byW. Seidel in 1939.
Properties of the original function and several modifications were ex-
2.1 ASTM Standards:
plored by Kaiser (Ref 2).
E115 Practice for Photographic Processing in Optical
2 The essential linearity of the Seidel preliminary curve within the 5 to
Emission Spectrographic Analysis
95% Trangeisanempiricalobservationbasedontheexperienceofmany
E135 Terminology Relating to Analytical Chemistry for
spectrographers (Refs 3-6). This linearity may not apply to all emulsions
Metals, Ores, and Related Materials
under all conditions, however (Refs 7 and 8 ).
E172 PracticeforDescribingandSpecifyingtheExcitation
Source in Emission Spectrochemical Analysis 4. Significance and Use
E305 Practice for Establishing and Controlling Spectro-
4.1 In order to derive intensity ratios from spectral line pair
chemical Analytical Curves
readings, an emulsion characteristic curve relating micropho-
E356 Practices for Describing and Specifying the Spectro-
tometer readings (either percent transmission or density) and
graph
relative intensity is necessary. The intensity ratios obtained
E409 Practice for Description and Performance of the
from the emulsion calibration curve are used to prepare
Microphotometer
analytical curves relating intensity ratio and concentration in
all spectrographic methods, that is, those methods using
3. Terminology
emulsions.
3.1 Definitions—For definitions of terms used in this prac-
4.2 Emulsion Calibration Curve—In spectrographic analy-
tice, refer to Terminology E135E135.
sis, an emulsion calibration curve represents the degree of
3.2 Definitions of Terms Specific to This Standard:
blackening of the developed photographic emulsion as a
3.2.1 density functions, n—the blackness of a spectral-line
functionoftheintensityofthespectrallinetowhichithasbeen
image is usually measured as transmittance, t; percent trans-
exposed.Theshapeandlocationofthecurvecanbeaffectedby
various factors:
This practice is under the jurisdiction of ASTM Committee E-1 on Analytical
4.2.1 Emulsion Properties—Type,preparationconditionsof
Chemistry for Metals, Ores and Related Materials and is the direct responsibility of
individual batch, and storage history;
Subcommittee E01.20 on Fundamental Practices.
Current edition approved April 10, 1997. Published June 1997. Originally
ϵ1
published as E116–56. Last previous edition E116–81 (1991) .
2 4
Annual Book of ASTM Standards, Vol 03.05. The boldface numerals in parentheses refer to the list of references at the end
Annual Book of ASTM Standards, Vol 03.06. of this practice.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
E116–97
4.2.2 Exposure Conditions—Wavelength and intensity of 6.3 Purchase and Storage of Emulsions— Purchase a quan-
radiation, spectrum range of radiation, exposure time, and titysufficienttolastforseveralmonths.Ifpossible,arrangefor
intermittency; rapid delivery of sealed packages in a frozen condition,
4.2.3 Instrumental Factors in Spectrograph and Micro- especially if the emulsion is highly sensitive or is intended for
the visible or infrared region. Store the sealed packages in a
photometer—Slit width, scattered light, resolving power, and
under some conditions, aperture and location of plate (see frozen condition, especially if the emulsion is highly sensitive
orisintendedforthevisibleorinfraredregion.Storethesealed
Practices E356E356); and
4.2.4 Development—Type and age of developer, time and packages at approximately−18°C (0°F) if facilities are avail-
able; if not, store at approximately 8°C (46°F). Bring the
temperature of development, and degree of agitation.
package to room temperature before opening. Do not refreeze
4.3 In order to obtain accurate intensity ratios, all these
after opening, but if kept unsealed in a refrigerator, use a
factors should be the same for both calibration exposures and
desiccant.
analyticalexposures.Somechangesinoperatingconditionsare
6.4 Rechecking of Calibration Curves— Contrast (γ) may
occasionally permissible (for example, a calibration curve
vary among plates within a batch, and may change slowly in
made with a continuous dc arc may be valid for a 120
storage, even at−18°C (0°F) (9). Calibration curves should,
pulse-per-second spark exposure), but any proposed change in
therefore, be rechecked as often as is found necessary with a
the above factors should be checked for its effect on the
given emulsion.
validity of previously prepared calibration curves. If a change
inoperatingconditionsiscontemplated,thebestapproachisto
7. Required Spectrographic Conditions
prepare a new calibration curve under the new conditions.
7.1 The following spectrographic conditions must be ful-
filled in order to obtain valid results:
5. Reference to this Practice in Standards
7.1.1 Alignment—It is assumed that the centers of all lenses
5.1 The inclusion of the following paragraph, or suitable
lie on the optical axis of the spectrograph, that the axes of
equivalent,inanyASTMspectrographicmethod(preferablyin
cylindrical lenses are properly oriented, and that the optical
the section on calibration) shall constitute due notification that
bench is parallel to the optical axis of the spectrograph. As a
this recommended practice shall be followed:
lens is moved away from the slit, the center of the lens must
Emulsion Calibration—Calibrate the emulsion in accor-
remainontheopticalaxis.Ifitdoesnot,performthealignment
dance with Practice E116.
procedure recommended by the manufacturer of the spectro-
graph.
6. The Photographic Emulsion
7.1.2 Vertical Uniformity of Illumination—Before the cali-
6.1 Selection of Emulsion Type—Select the emulsion in
bration filter or stepped sector is put in place, each line in the
accordance with the resolving power, contrast, speed, and spectrogram must be uniform in optical density over the entire
spectral sensitivity needed. As a rule, fine-grained emulsions
height to be used. Refer to Practice E356E356.
have higher resolving power and higher contrast than coarse- 7.1.3 Absence of Stray Light—Insofar as conditions permit,
grained emulsions, but lower speed. Photographic emulsions
light inside the spectrograph should fall only on the optical
are sensitive only in the ultraviolet and visible, blue to elements (for example, lenses, mirrors, prisms, gratings), and
˚
blue-green, spectral regions (λ≤ 4500 A), unless they have
not on their supports or on other internal parts of the spectro-
been specially sensitized for other regions. If the ultraviolet graph.
spectrum is to be photographed, especially in the second or
7.1.4 Minimization of Continuum—Lightfromincandescent
higher order of a grating spectrograph, use an unsensitized solids, for example, electrode tips, produces a spectral back-
emulsion. (This reduces interference from scattered visible
ground and should not be allowed to fall on optical elements
light and from overlapping spectral orders.) If the visible or inside the spectrograph. There are other possible sources of
infrared region is to be photographed, select an emulsion that
background in an arc (such as, molecular bands and unquan-
is sensitized as specifically as possible for the region under tized electronic transitions), but these should be negligible in
consideration.
the ultraviolet region under the recommended conditions.
6.2 Selection of Wavelength Filter—Ifaprismspectrograph 7.1.5 Wavelength Setting for Spectrographs in Which the
is used, or if the first-order ultraviolet region of a grating Range of Wavelengths Falling on the Plate Can Be Varied—
spectrum is to be photographed, do not use a filter. If the 2000 Theshapeandlocationofacalibrationcurvecanbeaffectedby
˚
to 2300-A region of a grating spectrum is photographed in the line shape. In some spectrographs of this type, the apparent
˚
second order, eliminate the overlapping 4000 to 4600-A shape of a particular spectral line varies with its distance from
radiation with a filter that absorbs this radiation but transmits the center of the plate. (This is particularly true for an Ebert
˚
the desired radiation. If the 2300 to 4000-A region is photo- spectrograph.) Thus, a calibration curve made on such an
˚
graphed in the second order, do not use a filter unless the instrument with the 3100-A region at the center of the plate
photographic emulsion is sensitive to visible light of wave- may not be valid if the wavelength setting is changed to bring
˚ ˚
lengths greater than 4600 A. If the visible or infrared range is the 3100-A region near the edge of the plate. If such a
photographed, use a glass filter to eliminate second and higher spectrograph is used, emulsions should be calibrated with the
orders of ultraviolet radiation. A wavelength filter may be same wavelength setting as will be used for analytical expo-
placed at any point on the optical bench, but a nonstigmatic sures.
position is preferable. 7.2 Light Source:
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
E116–97
7.2.1 General Considerations—The light source used for openingsufficienttoisolatethecenterthirdoftheimageofthe
emulsion calibration should have ample spectral lines in all light source; exclude the images of the tips of the electrodes if
wavelength ranges of interest. It should be operated for incandescent. Make the opening wide enough to accommodate
approximately the same period of time and in the same way the normal lateral motion of the discharge.
that the specimens will be exposed, that is, as a continuous dc
7.3.1.3 Elimination of Scattered Light, Direct Method—
arc, or as an intermittent arc or spark. For some emulsions at
Place a vertical-axis cylindrical-fused silica lens between the
certain wavelengths, the calibration curve obtained with con-
diaphragm (see 7.3.1.2) and the slit. With this lens, project an
tinuous illumination may differ from that obtained with inter-
imageofthedischargeontotheslit.(Thisimagewillbenarrow
mittent illumination. If tests show such a difference exists
and well defined in the horizontal direction, but blurred in the
under the user’s conditions, exposures for analytical purposes
vertical direction.) Open the slit wide, or remove it if possible,
should be referred only to a calibration curve derived using a
and look at the first optical element (lens, mirror, or grating)
similarlightsource.Typicallightsourcesaredescribedin7.2.2
which the light strikes after entering the spectrograph. If light
and 7.2.3. See Practice E172E172.
is falling above or below this element, or both, mask the
7.2.2 Continuous DCArc—Constructanall-ironglobulearc
cylindricallensatthetoporbottom,orboth,withopaquestrips
(10)asshowninFig.1.Thepelletshouldweigh50to100mg.
to remedy this condition (Fig. 2, “SideView”). If light falls on
Operate the arc at as low an amperage as possible; arcs of 0.7
eithersideofthefirstopticalelement,maskthesamelenswith
Ahave been found to be quite stable in a draft-free room with
vertical strips at the sides (Fig. 2, “Top View”).
a 230-V dc power supply and a suitable ballast resistance. The
7.3.1.4 Elimination of Scattered Light, Indirect Method—If
lower electrode is the anode. Make the arc gap as wide as
the front surface of the first optical element cannot be viewed,
possible. Shield the arc from cross-drafts.
measure or estimate the useful height of the first optical
7.2.3 Intermittent Radiation Sources— If an intermittent
element (h ), the distance (l ) from this element to the slit, the
c c
radiation source is used for calibration, it should resemble the
distance (l ) from the slit to the vertical-axis cylindrical lens
o
analytical exposure as closely as possible with regard to the
and the distance (l) from this lens to the intermediate image.
i
pulse duration, intensity, and frequency of individual pulses.
To find the height of this lens, which should be left open (h ),
o
7.3 External Illumination System:
use the equation: h =(h l)/(l + l + l). To find the width of
o o i c o i
7.3.1 Intermediate Image System:
this lens, which should be left open (w ), measure or estimate
o
7.3.1.1 Description of System—The most desirable way of
the useful width of the first optical element (w ) and use the
c
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