INDUSTRIAL AND ENGINEERIA\TG CHEMISTRY
94
VOI. 19. No. 1
Changes in Properties of Four Unblended Mineral Oils Produced by Prolonged Treatment with Ozone' By M. V. Dover and J. H. Cromwell ENGINEERING EXPERIMENTAL STATION. UNIVERSITY OF MISSOVRI,COLUMBIA, Mo.
T
HE effect of prolonged treatment with ozone upon some of the physical and chemical properties of four unblended mineral oilsz has been investigated with a view to determining, if possible, whether or not some relation exists between these properties and t.he stat'ic coefficient of frict'ion, as measured with the Deeley machine3between steel surfaces, :vhen each of these oils, treated and untreated, is used as lubricant. Two of the oils which have been investigated are paraffin-base and two are so-called asphaltic-base. The following properOies of each oil have been determined both before and after each treatment with ozone: specific gravity, surface tension, interfacial tension (oil-water), viscosity, acid number, iodine number, refractive index, and coefficient of static friction. Oils Tested Four samples of 100 per cent unblended, neutral oils, each from a different type of crude, were obtained from several refiners of petroleum products. Three of these lubricants had approximately the same viscosity, that of the fourth was considerably higher. Nos. 1 and 2 are paraffin-base and Nos. 3 and 4 are asphaltic-base oils. Experimental Methods DETERMINATION OF CoNsTAxTs-The coeficient of static friction was determined by means of a Deeley machine. The friction surfaces (steel) were carefully prepared as described in a former paper by one of the writer^.^ The scale readings are converted into coefficients of static friction by means of the following formula:6 1 Received August 28, 1926. Presented under the title "An Investigation of Some of t h e Changes in Physical and Chemical Properties of Four Unblended Mineral Oils Produced b y Prolonged Treatment with Ozone" before the Division of Petroleum Chemistry at the 72nd Meeting of t h e American Chemical Society, Philadelphia, Pa., September 5 t o 11, 1926. 2 T h e words "oil" and "lubricant" are used interchangeably throughout this paper. 8 Proc. Phys. Soc. London, 32, Pt. 11, 25 (1920); Dept. Scientific and Industrial Research of Great Britain, Report of Lubrication and Lubrication Inquiry Committee, 1920. 4 THISJOURNAL, 18, 63 (1926). 6 PYOC. Phys. SOC.L o n d o n , 32, P t . 11, 25 (1920).
F = - R X 10 C X L
where R is the reading on the machine, C, the constant of the machine (34.25), and L the load in pounds per square inch. For each load from five to ten readings were taken (if regular, five; if irregular, more). If the runs checked fairly well for all loads, only two were made, if the checks were poor, more runs were made. Acid number as determined by method D88-24T of the American Society for Testing Materials. Iodine number was determined by the Hub1 method. Specijc gravity was determined by the pycnometer method. Surface tension was measured with a Traube stalagmometer and reported in dynes per centimeter. Interfacial tension (oil-water) was measured by means of a Traube stalagmometer, allowing water to drop into oil, the same capillary being used in each case. Values are reported in arbitrary units. This method is a modification of the one used by Southcomb and Wells.6 Viscosity was measured with a Standard Saybolt universal viscometer. These constants were measured a t 25" C. in the cases of oils 1, 2, and 3, and a t 22" C. in the case of oil 4. Each of the above determinations was made in triplicate and the average of these reported. O z o s ~TREATMENT-The ozone was prepared from pure oxygen by a laboratory ozonizer.6 Each oil was treated with ozone for 8 hours a t room temperature and also for 16 hours a t 27' C. X o attempt was made to estimate quantitatively the ozone which, with some oxygen, was bubbled steadily (not rapidly) through about 250 cc. of oil in each case. This fact renders it difficult to repeat experiments exactly, but the authors believe that a fairly good idea of the effect of ozone or oxidation by ozone may be obtained from the measurement recorded in the following table : J . SOC.Chem. Ind.,39, 51T (1920) Am, SOC.Testing Materials, Tentative Standards, D85-24T; Bur. Mines, Tech. Papev 323A,Method 304. 8 Manufactured by the U. S Ozoiie Co., of Scottdale, Pa. 0
7
P h y s i c a l and C h e m i c a l P r o p e r t i e s of Oils T e s t e d VISCOSITY SURFACE INTERSaybolt SPECIFICGRAVITY TENSION F A C I A L TESSION seconds 15' C. 2 5 O C. Dynes/cm.
IODINE No.
ACID
Untreated 8 hours a t room temperature 16 hours a t 27' C.
8.68 9.02 8.90
Neutral
0.922 0.926 0.926
0.913 0.920 0.920
Untreated 8 hours at room temperature 16 hours a t 27' C .
13.70 7.99 4.86
Neutral
0.871 0.877 0.883
0.865 0.871 0.877
Untreated 8 hours at room temperature 16 hours a t 27' C.
8.88 8.63 6.81
0.5 2.7
0,887 0.889 0.893
0.880 0.883 0.887
0.1 0.8 1.8
(15.5' C.) 0.928 0.931 0,934
OZONETREATMENT
No.
I N D E X OF
REFRAC-
CO1,OR
TION
Oil S o . 1 1.5 2.3
34.45 34.83 34.29
1386.28 1379.82 1315.16
435 659 537
1.5095 1.5070 1.5048
3 N-. P. A. Slightly darker, bloom lost Slightly darker than shorter treatment, slightly hazy
1654.25 1269.14 1038.37
349 437 478
1.4808 1.4828 1.4812
4 N. A. P. Appreciably darker, but clear Much darker, very cloudy, appreciable amount solid settled on standing few days
2319.56 1542.14 1100.00
418 659 537
I .4779
1.4931
2 . 5 N. P. A. Considerablydarker,flocculentppt. Darker than after first treatment, hazy, and flocculent ppt.
3237.84 2050.73 1633.0
168 182 203
1.5097 1,5095 1,4987
Oil S o . 2 1.0 4.0
33.43 33.94 33.66 .
Neutral
~. .
34.12 34.16 34.93
1.4892
Oil No. 4 Untreated 8 hours at room temperature 16 hours a t 27" C.
10.1 8.6 6.4
(22' C.) 0.926 0.928 0,931
32.76 33.48 32.45
N. P. A. Much darker Almost black and considerable ppt.
3.5
January, 1927
INDUSTRlAL A1VD ENGINEERI,VG CHEMISTRY Observations
The average coefficients of static friction for the four oils are given in the accompanying graphs and the other properties in the accompanying table. Discussion
INTERFACIAL TEh-sIow-comparing the interfacial tensions (oil-water) of these four oils, both treated and untreated, with the corresponding coefficients of static friction, it seems impossible to assume that the lowering of the interfacial tension has a direct relation to the lowering of static coeffi-
95
oil No. 3 there is a slight increase in surface tension upon treatment for 8 hours, and a further slight increase upon treatment for 16 hours, with, in general, a decrease in the coefficient of static friction. In both cases the decrease is more marked when the treatment is prolonged. I n case of oil No. 4 there is a marked increase in surface tension with the 8-hour treatment, but a marked decrease with the 16-hour treatment. The coefficient of static friction decreases with the first treatment and increases with the second, though it is greater after the longer treatment than before the first treatment. The surface tension is lower after the 16-hour 'treatment than before the oil was treated.
I P
3
IO
20
33
40
60
50
70
80
90
100
Lbs p e r s q in
0 I9 0 28 0 27 0 26 C
0 0.25 024
u
0.23
g
022
c
0 0.21
z
02
I
t
0.19
3
?
8 GI8 2
0 I7 10
20
30
40
50
lbs per
eient of friction-i. e., to the increase of effiriency of these oils as lubricants-though Wells and Southcombg found this assumption to hold for several oils which they investigated. The results obtained in this investigation substantiate the view expressed by Wilson and Barnard.lo Bs one example, No. 4, upon treatment with ozone for 8 hours, shows a lowering of coefficient of friction-i. e., rise of eficiency-and a lowering of interfacial tension; upon further treatment with ozone the interfacial tension is lowered still more, but the coefficient of friction is raised for all loads. No. 3 shows a lowering in interfacial tension with both treatments with ozone; while the coefficient of friction shows, in general, a decrease for both treatments. Nos. 1 and 2 show a decrease of both interface and of coefficient of friction-i. e., increase in efficiency. SURFACE TENSION-The surface tension of oil No. 1 increases upon treatment with ozone for 8 hours but decreases upon prolonged treatment, though the coefficient of static friction decreases more with the 16-hour treatment than with t h e 8-hour treatment. The surface tension of oil No. 2 decreases after 16 hours' treatment with ozorie. I n case of 9
J . SOC.Chem. Ind., 39, 5lT (1920).
10
J . Automotive Eng., 11, 149 (1922).
54
60
70
e0
e0
100
in.
VIscosITY-Upon comparing viscosity with coefficient-of static friction, an interesting phenomenon is seen in the case of oil No. 4. At 22" C. this oil has a viscosity of 168 Saybolt seconds but a coefficient of static friction greater than oil No. 3, which has a viscosity of 418 Saybolt seconds. It is true that there are three degrees difference in the temperature a t which these viscosities are measured, but this difference would be in favor of No. 3-i. e., the viscosity would be less a t 25'' C. than a t 22" C., while the coefficient of friction, as measured, changes very little, if at all, with temperature. Again, oil No. 1, with a viscosity of 435 Saybolt seconds at 25" C. has an average coefficient of static friction of 0.286 for a load of 10 pounds, while No. 2, with a viscosity of 349 Saybolt seconds, shows a coefficient of static friction of 0.242 for 10 pounds load. This decrease in coefficient of static friction is shown not only for lighter loads, but for all loads from 10 to 100 pounds per square inch. ACIDNUMBER-In the paraffin-base mineral oils that have been investigated, both blended and unblended, the increase in acid number produced by ozonization was accompanied in each case by a lowering of coefficient of static frictionL i.e., the oils when used as lubricants. As for the asphaltic-base samples, it may be seen from curves for oils Nos. 3 and 4 that
INDUSTRIAL A N D ENGINEERING CHEMISTRY
96
this relation of acidity to the coefficient of friction is much less regular. IODINE NUMBER-Judging from these and former investigations, iodine number is an unsatisfactory property upon which to base any a priori opinion as to the lubricating value of an oil, or the power of the oil to reduce friction. It would seem, however, that, other things being equal, a more unsaturated oil would be a more efficient lubricant than a more saturated one. Oil No. 3, an asphaltic base oil with an iodine number of 8.88, shows a slightly lower coefficient of static friction than oil No. 2, a paraffin-base oil with an iodine number of 13.7. In a previous report by one of the writers" an analogous case was cited. 11
THISJOURNAL, 18, 499 (1926).
VOl. 19, N o . 1
Conclusion
The results obtained in the course of this investigation do not indicate a definite relation between any of these properties and the value of an oil as a lubricant. At the present stage of this work (further investigation is in progress) the authors hesitate to express further conclusions. Treatment with ozone reduces the coefficient of static friction of paraffin-base oils, so far invesitigated, when used as lubricants between steel surfaces; but similar treatment produces a less regular and less pronounced change in the asphaltic-base oils so far investigated. In general, the readings of the Deeley machine are considerably more regular after the lubricant has been treated with ozone than before treatment.
Separation of Minute Quantities of Gold from Ferric Oxide' By Edward Wichers2 NATIONAL
BUREAUOF
STANDARDS,
u. s.
DEPARTMENT O F COMMERCB,
ECENTLY it became necessary for the writer to determine a minute quantity of gold, .possibly of the order of 0.005 mg., in a residue consisting mainly of ferric oxide and weighing slightly more than 1gram. It was questionable whether a quantity of gold less than 0.01 or 0.02 mg. could be satisfactorily identified in such a material by fire assay methods. The color reaction with benzidines seemed to offer a suitable method for an approximate determination of the gold if it could be obtained in a chloride solution separated from the iron and from any other interfering substances. There are other sensitive methods for the detection of gold, but no comparative tests of this method with others were made after it was found possible to detect 0.001 mg. of gold per cubic centimeter and an absolute quantity of 0.0001 mg. of gold (0.1 cc. of the above solution contained in a small porcelain crucible). The reaction between the solution of benzidine (1 gram in 50 cc. of water and 10 cc. of glacial acetic acid) and dilute solutions of gold chloride is marked by a clear blue color, which rapidly fades and then changes to a violet shade less intense than the first color. It is not a characteristic reaction for gold. Ferric chloride and chlorine water give the same color, but cupric chloride does not cause a visible reaction. The color is doubtless that of an oxidation product of benzidine. Chloroplatinic acid gives a dark flocculent precipitate on standing, this reaction being sensitive to at, least 0.01 mg. of platinum per cubic centimeter if the test is allowed to stand overnight. Once the small quantity of gold was separated from the large mass of residue, the elimination of any interference from other substances (except chlorine) was simplified by using chlorine water to dissolve the metallic gold. Chlorine water, of course, has no effect on most ignited substances, but dissolves finely divided gold readily. Digestion on the steam bath and evaporation of most of the water usually served to remove all of the excess of chlorine, although special precaution was necessary to make sure of this. Too long digestion permitted a possible reduction of gold by dust particles or in other ways. Usually two or three portions of
R
Received June 29, 1926. Published by permission of the Director, National Bureau of Standards. Malatesta and di Nola, Boll. chim.-farm., 62, 461 (1013); J. Cham. SOC.(London), 104, 883A (1913). 1
1
WASHINGTON,
D. c.
chlorine water were subjected to digestion and evaporation under the same conditions, so as to provide checks on the elimination of all chlorine from the solution containing the gold. Experiments were made to determine whether the gold might be separated from the ferric oxide by fusion with potassium pyrosulfate. Volumes of gold chloride solution known to contain 0.005 mg., 0.01 mg. (duplicates), and 0.05 mg. of gold were added to each of four solutions of ferric nitrate equivalent to slightly more than 1 gram of ferric oxide. The solutions were evaporated to small volume and absorbed in filter papers, which then were burned off in porcelain crucibles. Each residue was fused with about 50 grams of potassium pyrosulfate until the melt was clear. The melts were dissolved in water acidified with sulfuric acid and filtered through S. & S. No. 589 blue ribbon papers which had been treated with a suspension of paper pulp and wet with dilute sulfuric acid. Although the filters were washed thoroughly with dilute acid, on burning off the paper the ash contained some finely divided ferric oxide, which yielded a colored suspension and thereby interfered with the subsequent color reaction. The fusion was therefore repeated, using a very small quantity of potassium pyrosulfate, and the resulting solutions were filtered in the same manner. The papers were burned off and the slight residue was digested with chlorine water. At the same time four similar porcelain crucibles containing 0.001 mg., 0.005 mg., 0.01 mg., and 0.05 mg. of gold as chloride were treated with chlorine water in the same manner. Two crucibles containing chlorine water only were used as blanks to insure the elimination of chlorine in the digestion and evaporation which followed. Upon the addition of several drops of the benzidine reagent all four samples gave a positive test for gold. In each case the color was less intense than that in the corresponding known quantity of gold which had not passed through the pyrosulfate fusion. It was apparent, however, that more than half of the gold was recovered in each case. By comparing the depth of color produced by the unknown material with that of the samples which had been separated from a similar quantity of ferric oxide, and assuming a proportionate recovery of gold, it was possible to give an approximate figure for the quantity of gold in the original material.
