NATIONAL BUREAU OF STANDARDS REPORT

4296

SPECTROPHOTOMETRIC

AND

COLORIMETRIC

ANALYSIS

SEVENTEEN GLASS FILTERS

DUPLICATING THE

RELOCATED AND RESPACED

UNION COLOR SCALE

FOR

LUBRICATING OIL AND PETROLATUM

FOR

ASTM COMMITTEE D-2

RESEARCH DIVISION IX

SUBMITTED BY

FISHER SCIENTIFIC CO.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

OF

by

John Co Schleter
U. S. DEPARTMENT OF COMMERCE

Sinclair WeekB, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

0201- 20-0203 September 1955 4-296

SPEC TROPHO TOMETRIG

AND

COLORIMETRIG

ANALYSIS

OF

SEVENTEEN GLASS FILTERS

DUPLICATING THE

RELOCATED AND RE8PAQED

UNION COLOR SCALE

FOR

LUBRICATING OIL AND PETROLATUM

FOR

ASTM COMMITTEE D-2

RESEARCH DIVISION IX

SUBMITTED BY

FISHER SCIENTIFIC CO.

by

John G» SchXeter

Photometry and Colorimetry Section

National Bureau of Standards

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, repi

unless permission Is c 25,D.C. Such perm

cal ly prepared If thi

Approved for public release by the

director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

n part, is prohibited

ndards, Washington

ort has been specifiiort for its own use.

Spect ro photometric

and

Colorimetric

Analysis

of

Seventeen Glass Filters

Duplicating the

Relocated and Respaeed

Union Color Scale

for

Lubricating Oil and Petrolatum

for

ASM Committee B-2

Research Division IX

Submitted by

Fisher Scientific Go<>

ABSTRACT

At the request of Research Division IX on Color, of

ASTM Committee D-2 on Petroleum Products., a spe etro photometric

and colorimetric analysis of a set of seventeen glass filters,

submitted by the Fisher Scientific Go 0 , has been carried out*.

These filters were manufactured to comply with the specifications

of the relocated and respaced Union color scale » It was found

that eight of the filters pass and eight of the filters fail to

pass the specification. One single-component was too large to

measure

.

I. INTRODUCTION

In 1950, the National Bureau of Standards completed the

derivation of a relocated and respaced Union color scale! (NBS

Research Paper RP2103) to replace t lie original Union sealed

The Fisher Scientific Company procured several sets of glass

filters manufactured to duplicate the relocated and respaeed

scale* One set of these filters, seventeen in number, were

submitted to NBS through Research Division IX on Color, of

ASTM Commit te D-2 on Petroleum Products, to ascertain whether

the filters complied with the specifications given in RP2103.

IIo SPECTROPHQ TOMETRIG MEASUREMENTS

Measurements of spectral transmittazxee of the glasses ~ , were made on a General Electric recording si>ectrophotometerj - equipped with slits equivalent to approximately 10 millimicrons
'

'

.
of spectrum for the spectral region 400 to 750 millimicrons.

This instrument is designed to measure transmitting

samples with a diameter of 25 millimeters or greater. It was

therefore necessary, because of the small size of these filters,

16 millimeters in diameter, to modify the optical path of the

instrument to reduce the beam size. A double convex meniscus

lens of approximately +3 diopters and large enough to intercept

both beams, was inserted into the optical path before the

decenter ed lens of the instrument. This supplementary lens

converged all of the incident light of the sample beam onto the

sample and produced a similar shape and convergence in the

comparison beam. The supplementary lens was mounted in a

blackened brass ring which fitted in the decent ered lens mount

of the spectrophotometer. The sample holder was made from

blackened- brass to both hold and position the sample and also

serve as a diaphragm in the sample compartment of the spectrophotometer. No diaphragm was used on the comparison side of the

instrument.

The calibration curves recorded on each graph sheet were as

follows: the curve of a sample of Coming 5>!2 didvinium glass for

the wavelength calibration; and the zero curve, and "Lens 100$

Curve" for calibration of the photometric scale. The "Lens 100$

Curve" was recorded with the supplementary lens and sample holder

in place.

- The spectral transmittanc es of the 30 components of Filters

B(0*5) through Q($.0) were measured ^by using the "normal" cam of

the spectrophotometer which gives 0$ to 100$ for full scale of

the graph sheet. The single component of Filter A(0o0)j, which

is clear glass, was too large to fit in the special holder and

was not measured.

In an attempt to obtain improved values of spectral transmittance, for low values of transmittance, a series of measurements was made for the uranium and selenium components (yellow

and red "cut-off" controlling components) of Filters D(l*5)

through Q(S.O), by using the "X5" cam which gives 0$ to 20$ for

full scale of the graph sheet.

Subsequently, components of Filters D(l«5) through Q(So0),

v/hich all contain two components, were measured in combination

to determine the spectral transmittanc es of the filters directly.

Measurements were made by means of both the "nonnal" and "X5"

cams. For these measurements, a ring-shaped spacer of celluloid

approximately O.lg millimeters in thickness was inserted between

the individual components to maintain an air space and avoid the

presence of interference patterns which would have occurred if

the components had been placed in contact.
.

.

.
-3

III. SFECTRQPHOTOMETRIC RESULTS

The spectrophotometric curves of each graph sheet were read

at 10-millimicron intervals between 400 and 750 millimicrons*

corrections being made for wavelength errors by comparing the

known wavelengths of minimum..transmittance of a Coming 512

didymium glass with those recorded on the graph sheets* The

photometric scale was corrected by means of the "Lens 100% Curve"

and the zero curve.

When the f! X5 rf cam was used with the supplementary lens

system, the stray light in the optical, system of the instrument

caused the zero curve to be recorded on the graph sheets at

approximately 0.2% rather than at 0.0%, with a slight decrease

towards longer wavelengths. The values of spectral transmittance

of this tf X5,f cam zero curve were read and extrapolations made for

the remainder of the visible spectrum in which the filters were

transmitting. These values of the WX5W asm sera curve were then

subtracted from the values of spectral transmittance of the filters

in the usual way for the zero correction.

It was found that for very low values of transmittance

(0,00$ to about 0.05%) the "normal " cam data generally indicated

lower values than the "X5" cam data* For this transmittance range

the "X5" cam data were adopted. In the transmittance range between

about 0 , 05 % and 20,00% the "normal" cam and "X5" cam data were

found to be in generally good agreement; and for this transmittance

range an average of the two sets of data were used. Above 20,00%,

of course, only "normal" cam data were available,

IV. COMPUTATION OF SPECTRAL TRANSMI TTANCE FROM COMPONENT DATA

The spectral transmittance data of the individual components

of the filters having two components were combined by multiplying

together, at each wavelength, the transmittance data of each

component to obtain the "computed" spectral transmitlances of the

filters. In performing these computations, four decimals were

maint aine d for Filt er s B ( 0 • 5 ) thro ugh L { 5 * 5 ) and six de cimals

were maintained for Filters M(6,0) through Q($.0).

V. COLORIMETRIC RESULTS

The values of spectral, transmittance of each filter were

converted to values of luminous transmittance, Y, and chromatic itycoordinates (x,y) , in accord with tfee

r1931 CIE standard observer

and coordinate system for colorimetry^ for CIE Source G (representing average daylight). The values of the chromaticity coordinates

(x,y) were then transformed into the uniform-chromaticity-scale

(UCS) system® for correlation with the specifications given in

RP2103 S by means of Equations (4), page 566, RP2103®
'

•
~4

~

As in the computations of spectral transmittance of the

filters from the data obtained from the individual components,

four decimals were maintained for the computations of the

chroma ticity coordinates (x,y) of Filters B(0.5~) through

L(5*5 )j and six decimals were maintained for Filters M(6.0)

through Q ( B • 0 )

,

to eliminate significant errors of rejection

in the dark and red end of the scale. All of the computations

of the chroma ticity coordinates (r,b) were made with four

decimals since in the final analysis only three decimals were

reported.

When corrections for light losses due to reflections at

the surfaces were attempted, it was noted that the corrected

luminous transnittances of the filters having two components

were all corrected to values higher than the maximum allowed

in the specifications. The unconnected values of luminous

transmittance, however, generally were within the limits of the

specification. Apparently, these filters were designed by the

manufacturer to be used in uncemented combinations. It was for

this reason that the direct measurements of spectral transmittance

of the filters were made with the thin ring-shaped spacer between

the components.

VI. ADOPTED VALUES

The values of the chroma ticity coordinates (r,b) s and luminous

transmit tances, Y, adopted for the set of filters were those

obtained from values of spectral transmittance computed from the

components rather than from the measured values obtained directly

from the combined filters because the precision of the results was

found to be greater.

The values the chroma ticity coordinates (r,b), and the

luminous transmit tances, Y, for Filters B(Q.5) through Q($.0),

obtained by the two methods, generally agree to within one in

the last place for fifteen of the sixteen filters, the greatest

deviation being 0.002 for the chromaticity coordinate, r, of

Filter N(6.5)«

The adopted values of the chromaticity coordinates (r,b),

and the luminous transmi ttanc es, I, together with the limits

for each filter, are given in Table I.

Figure 1 shows the chromatic ity coordinates, in the UCS

system, of the duplicate filters of the relocated and respaced

Union color scale. In this figure, it should be noted, the red

axis, r, has been divided into three sections. The large open

circles indicate the chromaticity tolerances.
‘ (
-5-

Figure 2 shows, on a square -root scale, the luminous

transmit tances , I, plotted against Union number. The open

circles of varying size indicate the transmittance tolerances.

The tolerance limits and luminous transmi ttances of Filters

P(7.5) and Q(&.0) are plotted on an enlarged ordinate scale

at the rigjit-hand side of the figure.

From Table I and Figures 1 and 2, it can be seen that

Filters E(2.0), F( 2.5 ) , G(3.0), H(3«5) s 1(4-0), J(4.5), and

L(5*5) pass the specifications for both chromaticity and luminous

transmittance. Filter B ( 0 • 5

)

is considered to pass the specifications even though the luminous transmittance is the maximum

allowed. Note that the viewing conditions present in the ASTM

Union Colorimeter require strict adherence to the chromaticity

tolerances, but that the transmittance tolerances are probably

more strict than necessary. Filter s K( 5 .0) , M(6.0), and N( 6 . 5

)

fail to meet the chromaticity tolerances, and of these, Filters

K(5*0) and N ( 6 . 5

)

fail to meet the transmittance tolerances

while Filter M(6.0) falls at the transmittance limit. Filters

C(1.0), D(1.5)> and P(7.5) fail to meet the transmittance

tolerances but pass the chromaticity tolerances. Filters

0(7.0) and Q(3.0) fall at both the chromaticity and transmittance

tolerance limits. Filter A(0.0) was not measured.

VII. SUMMARY

At the request of Research Division IX on Color, of ASTM

Committee D-2 on Petroleum Products, a spectrophotometric and

colorimetric analysis of a set of seventeen glass filters, submitted by the Fisher Scientific Co., has been carried out. From

this study, it has been found that eight of the filters pass the

specification for the relocated and respaced Union color scale,

as given in NBS Research Paper RP2103. Three of the filters fail

to meet the chromaticity tolerances, and of these three, two fail

to meet the transmittance tolerances while one falls at the transmittance limit. Three filters fail to meet the transmittance

tolerances but pass the chromaticity tolerances. Two of the

filters fall at both the chromaticity and transmittance limits.

The component of one single-component filter was not included in

the measurements because of size.

The author wishes to express his thanks to Messrs. W« A. Hall

and K. L. Kelly for their assistance in checking the data.
.

Xi .

. '

.

t

N

.
-6-

f Table I

Ghromaticity Coordinates in the UCS System (r,b), and Luminous

Transmit tances, Y, of Sixteen Glass Filters Submitted by the

Fisher Scientific Co. Duplicating the Relocated and Respaced

Union Color Scale for Lubricating Oil and Petrolatum.

Designation Chromaticity Coordinates Luminous Transmittance

of

Filter Max.

r

Min. Max.

b

Min. Max.

I

Min.

A(0.0) o.U*5 0.1*33 0.102 —— 0.090 0.95 -—

0.89

B(0.5) .168 0.161 .156 .071 0.066 .0S9 .89 0.89(*) .83

C(1.0) .1*95 .1*90 .1*83 .01*2 .035 .030 .80 .82 * .71

D(l.S) .527 .521* .515 .021 .012 .009 .70 .62 * •61

E(2.0) .558 .557 .51*6 .012 .001 .000 .58 .57 .52

F(2.5) .588 .583 .576 .008 .001 -.ool •16 .1*5 .1*2

G(3.0) .617 .612 .60S .007 .000 -.005 *33 .31 •29

h(3-5) .616 • 638 .631 .007 .000 -.00S .21* .23 .20

I(1*.0) .677 .671 .665 .00? .000 -.005 .163 .159 .u*i

J(l*.5) .709 .708 .697 .007 .000 -.005 .11? .109 .101

k(S.o) .71*2 .729 * .730 .006 .000 -.006 .087 .088 .075

K5.5) .776 •770 .761* .006 .000 -.006 .063 .059 .053

M(6»0) .811 .795 * .799 .006 .000 -.006 .oil .ol*l*(*) .036

N(6.S) .81*7 .832 # .835 .006 .000 -.006 .029 .030 * .023

0(7.0) .883 .871(*) .871 .006 .000 -.006 .018 .018(*) .oil*

P(7.5) .921 .912 .909 .006 .000 -.006 .0089 .0098 * .0073

Q(8.0) .962 • 95o(*) .950 .006 .000 -.006 .0028 .0028(*} .0022

* Filter fails to fall within tolerance limits,

fc*) Filter falls on tolerance limit.
• i • i .
CHROMATICITY

COORDINATES

LUMINOUS

TRANSMITTANCE,

(%)

FIGURE 2

)

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

I UNION NUMBER

-7-

REFSRENCES

1. D. B. Judd, L. Plaza, M. A. Belknap, A suggested relocation

and respacing of the Union Colorimeter scale for lubricating

oil and petrolatum, J. Research NBS 44, 559 (1950), RP2103.

2. ASTM Tentative method of tests for color of lubricating oil

and petrolatum by means of ASTM colorimeter, ASTM Designation:

D155-45T, ASTM standards, part III-A, p. $39, (1946)*

3. A. C. Hardy, A new recording spectrophotometer, J. Opt. Soc.

Am. _25, 305 (1935).

4. J. L. Michaelson, Construction of the General Electric recording

spectrophotometer, J. Opt. Soc. Am. 2&, 365(193$); also K. S.

Gibson, and H. J. Keegan, Calibration and operation of the

General Electric recording spectrophotometer of the National

Bureau of Standards, J. Opt. Soc. Am. 2&, 372 (193$).

5. Proceedings, Eighth Session, Commission Internationale de

L’Eclairage, Cambridge, England, September- 1931, p. 19 to

29; also A. C. Harcjy, Handbook of Colorimetry, Cambridge,

Technology Press, (1936); also D. B. Judd, The 1931 I.C.I.

standard observer and coordinate system for colorimetry,

J. Opt. Soc. Am. 22, 359 (1933).

6. D. B. Judd, A Maxwell triangle yielding uniform chromaticity

scales, J. Research NBS 14, 41 (1935) RP756; also J. Opt. Soc.

Am. 25 , 24 (1935).

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