AA’ALYTICAL EDITION
374
Vol. 2. No. 4
A Study of the Official Method of Bleaching Test of the American Oil Chemists’ Society‘ Chieh Ma and James R. Withrow CHEMICAL EKGINEERING DEPARTMENT, THB OHIO STATEUNIVERSITY, COLUMBUS,
I
The official method of bleaching test of the American Oil Chemists’ Society has been thoroughly studied with regard to the effect of varying the quantity of oil, the quantity of fuller’s earth, temperature, and time of bleaching, and the effect of stirring, with the result that the main factors of the test were found to be justified. It was concluded that 100 grams of oil might be used in bleaching test instead of the official 300 grams. The bleaching power of the official fuller’s earth reached its optimum efficiency at 7 per cent of the weight of oil. Although the official temperature was 120”C., arange of temperatures between 92” and 125“ C. was found most suitable for the bleaching test. Higher temthe bleaching peratures-130 ’ C. and u-decreased efficiency. With efficient stirring 1 minute was sufficient for making test, showing the 5 minutes official time to be ample. Prolonged time of bleaching for 72 minutes neither increased nor decreased the bleaching power of the earth to any appreciable extent. The Hess-Ives tint photometer was found very useful in measuring - the degree - of bleach when carefully used.
OHIO
ardized by the U. S. Bureau of Standards.) G l a s s oil s a m p l e boltlcs, or lubes.* These must have a 0at, smooth, polished bottom of clear colorless glass, not less than ‘/d inch inside diameter and provided with a mark to indicate an oil column 5114 inches in depth. DETERMINATION-Fill the tube or the bottle with the oil to be examined to a depth of 51/4 inches. Oil must be a t the temperature of 20’ to 24’ C. and must be clear and transparent. Filter through white filter paper a t 20-24’ C. if necessary to remove the turbidity to permit matching the color, and in such cases note on report that filtering is necessary. If, however, the oil or the fat under examination is not completely liquid a t 20’ C., heat until liquefied, and read the color at a temperature not more than 10’ C. above that which i t becomes completely liquefied. P 1a c e t h e Literature tube containing the oil in the tintometer and place alongside of it The literature in connecsuch yellow and red color glasses as are necessary for making the comtion with this work may be Theexpression, loo (T L, = per cent of bleach, was parison desired, observing the colors classified into two categoof the oil and the glasses through the very satisfactory for expressing the degree of bleach. ries+) the m e t h o d s o f eyepiece. Only one yellow glass and bleaching test and (2) the one red glass must be used to match the color of the oil in every case where the color standards are mentioned methods-of reading the color of the oil when bleached. establish the grade. Report the number of the yellow and the red BLEACHINQ TEs-The official method of the American to glasses which match the color of the oil; or if the standard combination is Oil Chemists’ Society ( I ) * gives detail of apparatus and deter- specified to be used (as prime for example), report whether the oil is prime mination. or off a s compared with the standard. (a) APPARATUS-scales, weights, refining cups, and stirring machine There is much literature on the Lovibond method. Parare t o be similar to those specified under Refining, but T-shaped paddles sons (10) used Lovibond glasses in 1907. Wesson (16) used I/* inch wide instead of 1 inch wide. Gas burners or electric heaters to heat the oil in the cup. a “ modified Lovibond tintometer” in connection with his work ( b ) DBTERMINATION-weigh 300 grams of refined oil into a refining on bleaching of oils with fuller’s earth in 1910. Bailey (8) cup; heat to 120’ C. and add 6 per cent of official fuller’s earth. Stir stated that Lovibond glasses “have not proved entirely satismechanically at 250 r. p. m. ( 110) for 5 minutes, not allowing the temfactory” because of the “lack of agreement which exists perature to fall below 105’ C., and filter through filter paper. After suffid e n t oil has passed the filter to insure clearness, collect a sample for color when different analysts determine the color of oils with the reading. Cool and read the color immediately a s prescribed under Color. Lovibond glass.” Two lines of studies followed--“The deThe official fuller’s earth prescribed above is to be obtained from the velopment of a new type of color comparator or a simple specsecretary of the American Oil Chemists’ Society. A fresh supply must trophotometer,” and “refinement in, or specific directions for, be used each year beginning August 1.
N CONNECTION with the investigation of clays for chemical engineering work, the writers became interested in certain questions connected with bleaching of oils from the viewpoint of the necessity and accuracy of each operation, specification as to the quantity of material, temperature of bleaching, rate and time of stirring, and the effect of variation of these conditions on the method. The official fuller’s earth of 1929-30 f u r n i s h e d by the American Oil Chemists’ Society and also cottonseed oil, refined but unbleached, were used throughout the work.
**
--
This method and methods of other authors are summarized in Table I. COLOR READINQ-Louibond Tintometer. The official method (1) specifies the Lovibond tintometer for color reading. (a) APPARATUS-Tinfomefer consists of a lightproof box with dull-black interior, containing a 75-watt “daylight” electric light bulb, a block of magnesia with a white reflecting surface set a t a proper angle t o reflect light vertically upward through the tube containing the sample of oil and through the standard color glasses alongside the tube of oil, and receptacles for holding the tube of oil and the color glasses. An eyepiece fits over the oil tube and color glasses so that the light passing through both may be observed simultaneously, Lovibond slandard glasses. Red and yellow, of suitable numbers to match the color of the oils to be examined. (Red glasses to be stand1 Received August 20, 1930. Presented before the Division of Industrial and Engineering Chemistry a t the 80th Meeting of the American Chemical Society, Cincinnati, Ohio, September 8 to 12, 1930. This may be procured from J. C. P. Helm, 705 Tchoupitoulas St., N e w Orleans, La., a t $0.50 per copy.
*
the use of Lovibond glasses.” Priest (13) of the Bureau of Standards, showed diagrammatically the actual discrepancies among the Lovibond glasses which had nominally the same grade when submitted to them for regrading the values. Hess-lues Tint Photometer. The use of this instrument was described by Kress and McNaughton (8) and also in the pamphlet furnished by the maker. I n attempting to adopt this instrument as standard for measuring color in oil industries, Wesson (15) made investigation of the instrument, and concluded that it can be made standard with the cottonseed and other industries. The adoption, however, was objected to by Smalley (14) on the ground that, inasmuch as this instrument also used colored glasses to read samples, its accuracy and permanence were not more certain than the Lovibond, even though it met every other requirement. He believed that the instrument was not capable of measuring slight variation of color, and that his reading differed with that of Wesson’s.
IND L’STRIAL AND ENGINEERING CHEMISTRY
October 15, 1930
Other Methods. Porter (22) adopted for color reading a set of color standards, consisting of twenty-one samples of oil “which had stood in the light long enough to have reached a condition of stability which showed a progressive range of color from the lightest to the darkest oil on hand.” These standards were marked from 1 to 21. He stated that “the only weakness of this method lies in the fact that the number of the color series does not vary uniformly in the amount of color contained, and hence these comparisons can give no information as to the absolute percentage of color removed.” Smalley (14) mentioned the use of a “solution proposed by Professor Ahrene, which consists of solutions of ferric chloride for yellow, cobaltic chloride for red, and copper sulfate for blue” for reading the color of oil. Bailey ( 2 ) proposed the use of B-L color comparator. I n his short summary of the history of oil colorimetry he pointed out that the earliest method used “was probably bichromate of potassium solution made up in definite concentrations.” The adoption of Lovibond was the next step after it. Keuffelt (7) claimed the K and E color analyzer to be very useful in reading oil colors. Hardy’s recording spectrophotometer (6) was perhaps the latest instrument mentioned in the literature to be very useful in oil reading, but it was not marketed a t that time. Table I-Summary QUAXTITYOF:
AUTEORS
Oil
Porter ( 1 2 )
104.4a
6 and 1 5
100 100 100 Boil water 100 9&92 Boil water
A. 0.C.S. official method
300 grams
...
6
BLEACB
c.
% 2 . 5 grams
200
TIMEOP
BLEACH
50
refining cups. A Hess-Ivea tint photometer was used in color readings. The first stirrers were glass rods but later brass stirrers with T-shaped paddles, 15/a by ‘/z inch, were used &s they gave efficient stirring action a t the specified rate, 250 r. p. m. A cabinet was constructed for the Hess-Ives tint photometer so that all light other than the source of illumination was cut off. The source of illumination was a 75-watt daylight lamp, except that data in Table I1 were obtained with an ordinary 100-watt electric bulb. After bleaching, the oil was filtered through filter paper in a hot-water funnel. The filtrate was received in a 90-cc. lipless thin-walled beaker t o a height of 5 cm. The color was read when cooled to room temperature. REPORTOF COLORREADIh-ffS-The reading of the Color of oil may be reported as total luminosity value. The perfect luminosity is 100 per cent for all color screens. The total of the three readings, red, green, and blue-violet, after multiplying by the respective luminosity factors, 0.19,0.71, and 0.10, equals 100. If the color is not perfectly white, the luminosity will be reduced. By multiplying the readings by the respective luminosity factors, and adding the products, we may obtain the “total per cent luminosity.”
of Various Bleaching Tests
TEMP. OF
cc. Parsons (IO) Parsons (If) Wesson (16) Maynard and Mallory (9) Bailey and Allen (3) Davidsohn (5) Benedict ( 4 )
a
Clay
375
STIRRINQ METHOD
COLOR
FILTRATION
READINO
Min. 5 3 3 Reguiar period
120
60 30 3
Shaking
Hot water funnel
Stir Stir
Filter while hot With or without suction
Agitation Stir Stir
Hot-water suction Through filtefpaper Filter paper steam-jacket funnel Filter paper, not below 105‘ C.
..... . ,
Stir at 250 r. p. m.
5
..................
Compare d t b standards Lovibond Lovibond LovIbond
Lovihnd
Oil bath
Need for Further Study of Method
I t is obvious that the bleaching test used by different authors varies in the quantity of material, time and temperature of bleaching, etc. The reasons for the conditions and specifications of the various methods were not found in the literature, nor was the effect found of variation of the conditions on the methods. Doubtless they were known to the original workers from the experimental data obtained in their use. The secretary of the American Oil Chemists’ Society knew of no publication covering the subject in question, so the writers undertook the following investigation. There appeared to be no color-reading instrument on the market which gave perfect satisfaction. For scientific investigations one was perhaps as good as another. The HessIves tint photometer appeared reasonably promising. The especial advantage of this instrument was that it gave numerical color values on a percentage basis, which was more intelligible than the color scale of the Lovibond glasses. For this reason it was used in this work. As Wesson (25) pointed out, proper precaution should be taken when using this instrument, such as should be applied to any instrument of precision. Experimental Procedure
All experiments were conducted according to the official method of bleaching test with the official fuller’s earth and with cottonseed oil, refined but unbleached, except in cases of purposely arranged variations. Beakers were used instead of
REPORTOF RESULTSOF BLEACHING TEsTs-The total per cent luminosity tells the color of the oil, but not the quantity of coloring matter removed nor the bleaching efficiency of the earth. I n order to express the result of bleaching test in terms of the quantity of coloring matter removed by the earth, the expression “per cent of bleach” is suggested, and is found from the following equation: loo(‘ - L , = per cent of bleach 100 - L where T = total per cent luminosity of bleached oil I, = total per cent luminosity of unbleached or original oil Table 11-Effect of Varying Amount of Oil Used Clay: official fuller’s earth, 6 per cent Oil: cottonseed, refined, unbleached Temperature: 120’ C. Time, 5 minutes
-
RED
EXPT.OIL
GREEN
I BLUE-VIOLE~rOTAL LUMI-
Lead- Lumi- Read- Lumiing nosity ing nosity
.:admg
Luminosity
1 Origi nul
84
15.96
54
38.34
0
2 3 4 5
300 300 300 300
91 93 93 93
17 29 17.67 17.67 17.67
84 83 83
83
58.93 59.64 58.93 58.93
6 7 8 9
100 100 100
93 92 93 93
17.67 17 48 17.67 17 67
83 84 83 83
58.93 59.64 58.93 58.93
100
%
%
Grams
%
OSITY,
BLEACH
T %
%
0
54.30
4s 48 45 46
4.8 4.8 4.5 4.5
81.02 82.11 81.12 81.12
58.22 60.85 58.68 58.68
45 46 45 45
4.5 4.6 4.5 4.5
81.12 81.72 81.12 81.12
58.68 59.90 58.68 58.68
0
4 K A L Y TICAL EDI T I O S
376
Effect of Variation in A m o u n t of Oil
Table I1 gives results of varying the amount of oil used in the official bleaching test. The total luminosity or per cent of bleach of Nos. 2 , 3 , and 7 differed from the rest, and the difference might be accounted for by the reason that the skill of manipulation and the reading of the color were not well developed. As a matter of fact, the end point of the instrument is not sharp but is within plus or minus one point. This is sufficient to cause a variation of 1 per cent or more. The bleaching obtained from 100 grams of oil is practically identical with that obtained from 300 grams of oil.
1'01. 2 ,
KO.
4
The data (Table IT and Figure 2) show that best bleachings were obtained from 92" to 125" C. At 130" C. quite a drop in bleaching is observed compared with that a t 125' C. I t drops more and more as the temperature elevates. Table IV-Effect
of Varying Temperature
-
RED
TOTAL J,VXI- BLEACH^
l&\IP.
TOSITY,
T -
% 24 55 74 84 92 100 110 125 130 140 160 200 215 a
92 95 97 98 100 100 100 100 100 100 100 99 89 L
=
0.8 2.8 3.6 4.0 4.6 4.5 4.3 4.6 4.4 4.3. 3 9 3.5 3.3
%
70
68.17 77.65 80.96 82.26 85.02 84.56 84 56 85.37 83.75 83.65 81.83 76.27 72.04
33.04 51.74 58.67 61.50 67.50 66.50 66.50 68.26 64.73 64,52 60.56 48.47 39.28
58 97 per c e n t
Effect of Variation of Quantity of Earth
Bleaching tests were made according to the official method except the quantity of earth was varied from 1 per cent to 15 per cent. The source of illumination for the Hess-Ives tint photometer was a 75-watt daylight bulb in the place of the ordinary electric bulb previously used. Higher luminosity value was obtained with the daylight bulb. The results, given in Table I11 and Figure 1, show that for this particular earth the efficiency of bleaching was highest for the first 4 per cent of earth used. At 7 per cent the curve tended to level off and the bleaching power of the earth was about exhausted under the conditions of the experiment. At least above 7 per cent the amount of earth used gives no comparable advantage. Table 111-Effect FULLER'S
1
2 3 4 5 6 7 8 10 12 15
I
of Q u a n t i t y of Official Fuller's Earth
RED
92 96 98 100 100 100 100 100 100 100 100
LUMI-
17.67 18.24 18.43 19.00 19.00 19.00 19.00 19.00 19.00 19.00 19.00
I
67 75 81 85 86 86 88 88 88 89 89
47,57 53.25 57.51 60.35 61.06 61.06 62.48 62.48 62.48 63.19 63.19
I
6 20 30 36 38 41 51 50 50 50 53
0.6 2.0 3.0 3.6 3.8 4.1 5.1 5.0
5.0
5.0 5.3
25.78 ~ 3 . 4 9 42.41 78.94 5 4 . 2 8 8 2 . 9 5 63 00 8 2 . 9 5 63 on 84.16 6 5 . 6 3 8 6 . 5 8 70 81, 86.48 70.67 86.48 70.67 87.19 72.21 87.49 72.87 !5.84
,
Effect of Temperature
Bleaching tests were made according to the official method, but varying from room temperature (24" '2.1 to 215" C.
Temperature Figure 2-Effect
- "6.
of Varying Temperature o n t h e Official Method of Bleaching Test
The lowering of the bleaching due to the increase of temperature may be explained by assuming that either the viscosity of the absorbed or adsorbed coloring material is lowered a t temperatures higher than 125" C., and flows back into solution again, or that there is some internal change in the coloring matter of the oil itself under the influence of earth a t that temperature. If the latter were true two distinct reactions may have occurred in the batch of bleaching: (1) At temperatures below 125' C bleaching action took place. (2) Above 125' C. coloring matter developed by the oil and this new coloring matter could not be absorbed by the earth present, which was long ago saturated with the old coloring matter.
It is also possible that a hydrate such as clay gradually ceases to function as a bleaching agent above 125" C. for vegetable oils The earth, on the other hand, might change its structure under these conditions. The porosity might be reduced so that the power of holding the absorbed material would be lessened, and under high temperature and continuous stirring the coloring material would go back into solution.
I r D USTRIAL AiYD ENGIXEERl'iVG CHEMISTRY
October 15, 1930
Effect of Time of Bleaching
Bleaching tests were made according to the official method but varying the time from 1 minute to 72 minutes. The official time was 5 minutes. The results are shown in Table V.
377
With efficient stirring the bleaching reached its height in the first minute. This means that the bleaching action is very fast. Bleaching for more than 1 hour gave no added effect. Literature Cited
T a b l e V-Effect
of Variation of T i m e of Bleaching Test
RED
I
Min.
TOTAL
ing
nosity
43 44 45 44 44 45 44 45 45 44 44
4.3 4.4 4.5 4 4 4.4 4 5 4 4 4 5 4 5 4 4 4 4
70
7c
85 84 85 84 85 85 85 84 85 84 85
60.35 59.64 60.35 59.64 60 35 60.35 60.35 69.64 60.35 59.64 60.35
L = 53.97 per cent
70
70 83.65 83 04 83 85 83.04 83.75 83 85 83 75 83 14 83 85 83 04 83 75
%' 64.52 63.19
ti:!: 64.74 64.95
i:,:: 64.95 :::;!
(1) American Oil Chemists' Society, Official Methods, p. 17 (1919' (2) Bailey, J . Ozl Faf I n d . , 2, No. 1, 8 (1925). (3) Bailey and Allen, Cotton Ozl Press, 7, Xo. 8, 36 (1923). (4) Benedict, J . Ozl Fat I n d . , 2, KO. 2, 62 (1925). ( 5 ) Davidsohn, Seifcnsieder-Zfg., 60, 648 (1923). (6) Hardy, J. Oil F a f I n d . , 6, Xo. 9, 31 (1929). ( 7 ) Keuffelt, Ibid., 2, KO. 1, 14 (1925). (8) Kress and McNaughton, J. IND. ENG.CHEM.,8, 711 (1916). (9) Maynard and Mallory, Chem. Met. Eng., 26, 1074 (1922). (10) Parsons, J . Am. Chem. Soc., 29, 598 (1907). (11) Parsons, Bur. Mines, Bull. 71, 23 (1913). (12) Porter, U. S. Geol. Survey, Bull. 316, 268 (1907). (13) Priest, J . Oil Fat I n d . , 6, KO.9, 27 (1929). (14) Smalley, Cofton Oil Press, 2, Xo. 3, 42 (1918). (15) Wesson, Ibid., 2, No. 3, 52 (1918). (16) Wesson, Trans. A m . Ins!. Chem. E w , 3, 327 (1910).
Early Stages of Oxidation in Rubber' A Quantitative Application of the Pyrrole Test J. W. Temple, Sidney M. Cadwell, and Morris W. Mead, Jr. UNITED STATES RCBBERCOMPANY, DEVELOPMENT DEPARTMEXI', PASSAIC, N. J.
The pine splint-hydrochloric acid test for oxidation holding a pine splint in the products of rubber has been developed in a quantitative vapors. They obtained posithe simple products of way. The technic and special apparatus are fully tive tests with both raw and its ultimate oxidation described. cured rubber which had been many stages intervene. For Data from application of the test to a wide range of oxidized. I t has been found the practical rubber techcommercial stocks are given. Its use in following early possible, through a number nologist chief interest in this stages of oxidation as they occur in accelerated aging of refinements, to increase oxidative process is centered of vulcanized rubber is described, and attention is greatly the sensitivity of the in that portion which has called to an apparent difference between oxygen aging reaction, and to use the inoccurred up to the time when and heat aging. Evidence is cited that the substance tensity of color developed as the rubber has so c h a n g e d which gives the test, presumably levulinic aldehyde, a comparative measure of that it has lost its value as is formed independently of, and previous to, the actual the amount of this particurubber. physical deterioration of the rubber. lar oxidation product in a This paper describes a semisample. The sensitivity is quantitative application of the well-known pine splint-hydrochloric acid test for pyrrole such that it is usually possible to get positive tests before derivatives which the authors have found useful in following there is any evidence of physical deterioration as shown by the early stages of oxidation in rubber, particularly in vul- tensile measurements. canized rubber. It consists essentially of digesting the aged Testing Technic rubber with fused ammonium acetate, distilling with steam, and treating an ether extract of the distillate with an alcoFigure 1 shows an apparatus which was developed for use holic pinewood extract to which has been added hydrogen chloride. A red color develops, which is compared with a in the test. LL'ith several of these in use simultaneously three or four analyses can be finished in from 20 to 30 set of permanent standards. Several different observers have noted that water will minutes. The rubber sample is cut into thin slices and accurately extract from oxidized rubber a substance which can be condensed with ammonium acetate, and thereupon gives the weighed. One gram is suitable for a stock only slightly pyrrole color reaction with a pine splint. Bruni and Pe- aged, with smaller samples in proportion for those which lizzola (.e) credit Gorter with being the first to record this are further advanced in oxidation. The sample is placed fact, and cite several others who verified it. The active in the short-neck flask and from 2 to 3 grams of crystalline substance is generally assumed to be lewlinic aldehyde, ammonium acetate are added. After the delivery tube has since the y-ketoaldehydes give the reaction, and since been placed in position, the flask is gently heated with a small Harries (8)and Whitby (6) have identified it among products direct flame until the acetate is completely fused, using care from rubber ozonide and oxidized rubber, respectively. t o avoid charring the rubber. Gentle heating is continued Bruni and Pelizzola ( 2 ) simplified the test by heating for from 3 to 5 minutes in such a way that the level of conthe rubber directly with fused ammonium acetate and densing vapors on the sides of the flask rises barely to the ground-glass fitting. After the flask has cooled, 8 to 10 cc. Presented before the Division of Rubber 1 Receired April 15, 1930. of water are added, and this is then distilled over into the Chemistry at the 79th Meeting of the American Chemical Society, Atlanta, long-stemmed flask as a receiver. Most of the ammonium Ga., April 7 t o 11, 1930.
ETWEES rubber and
B
