Measurement of Bloom of Lubricating Oils' BY I-. M. Henderson and H. C . Cowles, Jr. THBA T L A N ~RIIPININO C Co.. P X I L A D R L PSA ~A,
The Iacs tint photum&i- has been modifjyd in such a manner as t o permit its use in measuring the bloom uf iubricatiiig oils. The ainount ?f cach o,ff;wstandard colors rejected by the oil is quaniitatiae(y measured and a meansf ,o expessin~rthe bloom o,f the oil i n definite nunierical terms i s ,ciorii. 1 IIAS l i w i viistoimiry ti, (1 rilic tho c o h r iiE it niiwrnl oil o h s e r d hy reflected light with siicli cxpressioiis as lien grcen," "olivr grccii," "liliie g m x i ~ ' 'and the like. Such t.ernis are suhjcct to loope iiitcrpret:iti(in by different
I,:(
observers. It is iiot possihle to specify with any great precision the reflected color-i. e., bloom, of ail oil by such terminology, or to indicate accurately the snmller variations in different. lots of a given oil. The situation has led to a search for a numerical expression. It does not seem feasible to match the bloom of luhric:iting oils with the colors of soluiioiis of organic dyes or mirieral pigmcnls. The Ives tint pliotometer has been used in many industries Eor measuring the reflected color of opaque bodies and this instrument offered possibilities for the measurement of the bloom of oils. A n atteiqrt was made to use it in tho same manner as it is uspd for measuring the colors reflected by opaque object,s. A crystallizing dish containing the oil was placed on a black surface and the colors reflected Erom the oil were determined. The light did not strike the surface a t a satisfactorv angle. R,eadirigs o;i the photometer scale indicated almnst equal absorption of all t h o s p e c t r a l colors and showed that not more than 3 per cent of the light striking the oil surface was reflected. From theresultsthus obtain&, i t was evident that the light falling on the oil s u r f a c e must have about thirty-two times the intensity of the light originally supplied in the app a r a t u s . The light Figure 1-Modified k e a Tint Phorometer ravs must strike the oif at such an angle as to reflect the maximum bloom colors thrnngh the eye piece of the tint photometer. Modification of t h e Ives Tint Photometer Figure 1 shows the tint photometer as modified for thc determination of bloom. A sheet metal septum, A, was fitted into the light chamber to prevent the light from the photometer lamp striking the oil. An anxiliary lamp, B, was installed so that a beam of light might be cast on the surface of the oil at an angh: of 45 degrees. This lamp was placed in a metal tube approximately 7.6 em. in diameter and 22 em. long, which was adjusted in sueh a manner that its lowest point was 19 em. above the table top. When an Received August 28, 1926. Srerented before the Division of Petroleum Chemistry st the 72nd Meeting of the American Chemical Society, Philadelphia, Pa., September 5 t+ 11. 192B.
:auxiliary 1;inip 1 ~ : ~iiscd s uf aiicli j x i w r blint the light roiiected from the oil surface was 32 times as great as originally supplied by the photometer lamp, the oil heated too rapidly. It was therefore ne ary to interpose a screen with a density of 0.6 in the path of tho rays from the photometer lamp. This permitted the use of an auxiliary lamp of about onefourth the intensity that rvould otherwise ha.re been required. Wrattan Neutral Filters were used as screens because they ean be duplicated with sufficient accurscy aiid are easily obtained, The spectrum of the auxiliary light must closely approximate that nf the photometer lamp. The ordinary 7.5-watt RIazda bulb proved quite satisfactory. Table I shows t h e effect of variation in tho illumination and elevation of the oil surface. Diffused light 8howsapprcciably less bloom t h s e the open Mazda, while a narrow slit of light is of no advantage. The best results were obtained with a n elevation of the oil surface at approxi_, mately 10.5 mi. and with the lowest point of the light tube 2.5 . , , . , ~ , em. higher. The auxiliary lamp was standardized in ; somewhat the same 3 manner as the regular photometer lamp save for certain details which areenumerated below. The surface of the horizontalmap"8 /*". nesia block was raised Figure 2-Vmistlon in Bloom with Tem-tore to a level 17 cm. above the bottom of the tint photometer, and the lower edge of the lamp tube placed approximately 3 cm. above the magnesia block. A neutral filter with a density of 1.5 was then inserted at I)in the path of the rays from the auxiliary light, the filter of 0.6 density remaining in the path of the rays from the photometer lamp, at C . The end of the metal t u h was moved toward or away from the magnesia block until the field of light in the eye piece balanced that of t h e standard lamp. The magnesia block was maintained at such elevation as would give maximum reflection. A pointer which had been attached to the side of the photometer was then brought into contact ii~iththe top of t h e magnesia hlock and its position fixed. Y
~
I
Type of Container Considerable difficulty was experienced in securing a container for the oil which would reflect little or 110 light. Of those tried, the most satisfactory was a crystallizing dish (40 mm. deep) which had been sand-blasted inside and out and then painted on the outside with a doad black lacquer, Eveii this container reflected a small amount of white light. It must he noted that in using a container
I N D USTRIS L A N D EAVGIiVEER14VGCHEMISTRY
January, 1927
75
when the bloom of the oil was measured, each absorption value given in this paper is 1.5 less than the true absorption by the oil. The figures given are the instrument scale readings. If absolute absorption is desired it is only necessary to add 1.5 to these values.
of the above type, the color measured was that reflected from an oil-air interface. Colors reflected from this surface were found to be somewhat different from those reflected from an oil-glass interface. On account of obvious difficulties in the use of the oil-glass interface and the different color
f
kP YB
c
BG
o
r
J
?
COLOR
Figure 3-Effect
Figure 4-Olive
of Blending
absorptions encountered with various glasses, the oil-air interface was adopted as the standard. Most lubricating oils are quite transparent to red but rather opaque to blue rays. Consequently, in the case of pale oils the amount of red which is reflected from the oil-air interface is augmented by the red rays reflected from the inner surface of the container, while the amount of blue reflected remains unaltered. This condition changes the shape of the bloom curve. To reduce this error to a minimum, the depth of the oil layer under observation was made as great as practicable for convenience, 35 mm. Table I1 shows the variation in bloom with increasing depth of oil. Table I-Effect
of Height of Oil Surface, Auxiliary Light, and Direction of Light Rays o n Bloom Readings
ANGLE BELIGHT H E ~ G HOF T TUBEA N D OIL
TWEEN
OIL SURFACE
SURFACE
Degrees
Cm.
30 60 20 20
16.5 16.5 21 22
ABSORPTION
OF
LIGHT Cm,
VB
Red p a r a f i n oil 19.0 0.49 19.0 0.48 23.5 0.52 24.6 0.57
BG
G
0.42 0.44 0.47 0.50
0.50 0.49
0.41
0.41
Y
R
0.53 0.54 0.60 0.62
0.62 0.59 0.68 0.70
Filtered cylinder oil 45 45
45 45
45a
15.25 17.8 17.8 20.3 17.8
16.5 19.0 20.3 23.0 20.3
0.31
0.035 0.065 0.126
0.31 0.38 0.55
0.040 0.12 0.29
0.10 Impossible 0.115
... ...
0.075
... ..
.
0.18 0.25 0.40
Average wave length of maximum transmission of each color filter. V B = Violet-blue 450pp Y = Yellow 575 R = Red BG = Blue-green 495 650 G = Green 540 0 = Orange 630 a Ground glass D = 0.58 at end of tube.
Determination of the Bloom
To determine the color reflected from the surface of an oil the neutral filter of 1.5 density a t D and the magnesia block are removed. The oil, which is contained in a black crystallizing dish, is placed on the adjustable table and raised until the surface of the oil touches the pointer. The series of color filters is then inserted in the slot of the eye-piece and the absorption of each color read on the instrument's scale. The absorption thus noted is expressed as the common 1 logarithm of For example, if 25 per cent of reflection the light is reflected, the absorption is equal to 0.602. The observations were made upon the oils a t a temperature of approximately 35' C. and in a dimly lighted room. Inasmuch as a filter of density 1.5 was in the path of the iight from the auxiliary lamp when it was standardized against the photometer lamp and this filter was removed
Oils
Figure &Green
Oil and Mineral Oil Table 11-Variation
Variation i n Depth of Oil
i n Bloom Due'to
ABSORPTION OIL
DEPTH O F OIL Mm.
A
0.3
A A A B B
12 24 36 24 36 24 36
C
C
VB
BG
0.81 1.02 0.98 0.99 0.66 0.76 1.25 1.20
0.81 1.02 1.07 1.08 0.79 0.88 1.25 1.17
G 0.79 0.99 1.01 1.01 0.80 0.95 1.08 1.07
Y
O
R
0.81 1.00 1.00 1.00 0.84 1.04 0.82 0.99
...
0.80 1.08 1.07 1.13 0.84 1.10 0.71 0.97
1.01 1.02 1.07 0.85 1.06 0.71 0.96
A = light distillate, 1.75 N. P. A,; B = filtered oil, 1 N. P. A , ; C = debloomed oil 3.5 N. P. A .
Influence of Temperature on Bloom
Figure 2 indicates the influence of temperature on the readings, particularly in the case of paraffin distillates. At higher temperatures these oils reflect less of all the colors, with the least change in the blue, but upon cooling to the original temperatures, they assume their original blooms. The colors reflected by cylinder oils vary but little with change in temperature, as shown in Table 111. The blooms of these oils have been expressed graphically by plotting the common logarithm of
1
as ordinate against
reflection
the color of each light filter as abscissa. AS a matter of fact, i t is t h e average wave length of the maximum transmission of each of the light filters that has been plotted on t h e a b s c i s s a s . This accounts for the u n e q u a l spacing of the spectral colors in the graphs. Table 111-Variation
i n Bloom of Cylinder Oil with Temperature
TEMPERATURE OIL
ABSORPTTON
OF OIL
c.
VB
BG
G
Y
0.54 0.58
0.31 0.35
0.23 0.27
0.27 0.30
~
Filtered cylinder Filtered cylinder
25
60
R ~~
0.46 0.50
Effect of Blending
A mixture of equal parts of a decidedly blue distillate and a bright green cylinder oil gave a green blend closely approaching the reflected color of the cylinder oil. I n common with cylinder oils, the bloom of this blend was but little affected
INDUSTRIAL AND ENGINEERING CHEMISTRY
76
by rise in temperature. The modification of the bloom of a light motor oil by the addition of olive oil in an amount equal to four times its volume was comparatively slight and quite disproportionate to the amount of mineral oil in the blend. Figures 3 and 4 show the blooms of the two blends in comparison with those of their constituents. Results of Bloom Determinations
A number of 4-ounce sample bottles of oil were inspected for their bloom and classified as they appeared to the eye. The c l a s s i f i c a t i o n s w e r e g r e e n , bluegreen, and blue oils. The fourth class included oils which had been sun debloomed and those commonly considered bloomless. The first three groups are shown in Figures 5, 6, and 7. The few cases i n w h i c h t h e graphs indicate a COLOR somewhat d i f f e r e n t bloom from t h a t Figure 7-Blue Oils which was apparent to the eye is due to the change from an oil-glass to an oil-air interface. I n Figure 8 it is shown that the deblooming of an oil greatly increases its ability to absorb blue light. These oils, in common with fatty oils, give a reflected color similar to their transmitted color. The reflected colors of asphalt and medicinal white oil (dark gray with a blue-green tint) are quite similar. It is
Vol. 19, No. 1
Y
probable that a container more nearly black than the one available a t present would show the white oil to be as dark as the asphalt when viewed by reflected light. I n general, the light distillates are darker by reflected light than are the cylinder oils. As is the case with all colored objects, the reflected color of an oil is indicated by the relative absorption of the different colors of white light. The shape of the curves here presented indicates the bloom of the oil by showing the relative amounts of the five principal colors. The steepness of the curve on each side of the color least absorbed shows the brightness of t h e c o l o r , or i n o t h e r w o r d s , shows how nearly monochrom a t i c t h e color is. For example, a curve with a deep trough in a 5 t h e green shows a 5 b r i g h t green, while the curve for another ,2 oil, which is predominantly green, may be 10 more nearly horizon'' talandif sorepresents a dull g r a y - g r e e n '8 BL 6 I O R COLOR bloom. Furthermore, Figure 8-Debloomed and Bloomless Oils two bloom curves may have the same shape but one may lie higher than the other. If such be the case, the two oils reflect the same color, but the one corresponding to the higher curve is darker because it reflects less light. I n addition to the values of reflection a t various wave lengths, the value of the total reflections may be obtained with the instrument. 21
Diethyl Sulfate in the Examination of Hydrocarbon Oils' By J. N. Taylor BIOCHBMIC DIVISION, BUREAUOF ANIUALINDUSTRY,
ARAFFINS and naphthenes are usually differentiated from aromatic and unsaturated hydrocarbons by sulfonation. The procedure described by Chapin,* in which dimethyl sulfate is employed, is often used in a preliminary examination of such mixtures. As it is poisonous, dimethyl sulfate may be safely used only if carefully handled. Diethyl sulfate, its homolog, is reported to produce no toxic effects, which would appear t o give it an advantage. There is no difference in cost. I n order to determine its efficiency when applied to mixtures of hydrocarbon oils, tests were made and the results were compared with those obtained by the use of dimethyl sulfate and of sulfuric acid.
P
Experimental
Mixtures, in varying proportions by volume, of petroleum oil and benzene were prepared. The petroleum oil was a water-white, high-boiling, refined petroleum distillate, with an initial boiling point of 265" C. and a specific gravity of 0.858 at 25' C. It was immiscible with both dimethyl and diethyl sulfate and was unacted upon by concentrated 1
2
Received September 22, 1926. U.S. Dcpt. A g r . , Bur. Animal Ind., Circ. 167 (1911).
WASHIIGTON,
D.
c.
sulfuric acid. The benzene employed is commonly known as "commercially pure benzol." Its boiling range was within 2" C. and included the true boiling point of benzene. It had a specific gravity of 0.870 a t 25" C., was completely miscible in all proportions with both of the alkyl sulfates, and left no residue upon sulfonation. The alkyl sulfates used were refined, water-white grades, with but a trace of acidity. All of the materials were purchased direct from manufacturers. Original Method
Five cubic centimeters of the mixtures and 8 cc. of the alkyl sulfates were placed in glass-stoppered Egertz tubes. The tubes were vigorously shaken and placed in a constanttemperature water bath and the volumes of the resulting upper layers were measured a t 25" C. Sulfonation was accomplished by the method described in Forest Service, Circular 112. The operation was carried out in Babcock cream bottles. Upon completion the volumes of the oil residues were measured at 25" C., with the results shown in Table I. I n its upper range, the partition curve for diethyl sulfate (Figure 1) is in close agreement with the sulfonation curve.
