Mav. 1926
INDUSTRIAL AAVDE-VGINEERING CHEMISTRY
527
A Possible Test for the Oiliness of Oils’*’ By Augustus H. Gill and Helen Gill’ OIL AND GAS LABORATORY, MASSACHUSETTS INSTITUTE OR TECHNOLOGY, CAMBRIDGE, MASS.
I
T HAS long been known that the viscosity of a n oil does not fully measure its lubricating power. Parish4showed in 1910 that of two oils of the same viscosity the coefficient of friction was 14 per cent less in one case than in the other. Later work by Wilson5 indicates that there is a very close relationship between friction and viscosity tests-that the friction machine is simply a glorified viscometer. Kone of the proposed methods for determining the oiliness or greasiness being satisfactory it occurred to the senior author that possibly the method used by Perrotta for measuring the “length” of carbon (gas) blacks might be adapted to oils. Perrott mixed different carbon blacks with the same sample of linseed oil and meajured in the MaclLIichael viscometer the deflection of both the oil itself and the mixtures a t different speeds. The deflection corresponds to the pressure in Binghain and Green’s plastometer, and the speed of rotation corresponds to the volume flowing through the capillary. Perrott states that “1ongJJ~arbon blacks have lower cohesion than “short” blacks and they show less “spread” between the curve (or rather straight line) of the oil itself and that of the oil mixed with the carbon black. Carbon black being chemically such an active agent and likely to change the composition of the oils, other more inert substances were sought. It was hoped that some finely divided metal similar to those used in shafts or bearings could be used-that is, iron, brass, antimony, lead, or tin. This had to be abandoned on account of their specific gravities, as even iron reduced by hydrogen settled so rapidly out of the oil as to render its use impossible. “Aluminum bronze’’ powder, after dissolving out the stearic acid used in its manufacture with ether, was only fairly satisfactory. The powder finally employed was diatornaceous or infusorial earth which had been ignited for half an hour at a red heat to burn out the organic matter. Procedure
The deflection of the oil by itself is first measured in degrees MacMichael a t four to six different speeds of rotation, varying from 5 to 80 revolutions per minute, a t 26” C. Ten grams of the infusorial earth are mixed with 100 cc. of the oil to be tested, the mixture is heated to 25’ C., arid its deflection in degrees Machlichael read a t four to six different speeds of rotation as above. These observations are plotted, with degrees MacMichael as ordinates and revolutions per minute as abscissas. The ‘‘spread” or difference between the two straight lines obtained with the oil, and with the mixture of oil and earth, is read off in degrees XfacPvIichael a t 70 r. p. m. and changed to centipoises by a similar plot using glycerol solutions of known gravities to give solutions of known viscosity. Two different wires are employed for heavy and light oils. The oils are arranged in pairs indicated by brackets for ready comparison, using oils of closely corresponding absolute viscosity. The results are shown in Tables I and 11. All the oils were used in a fresh condition-that is, they had not been exposed to the air. The organic oils were all of 1 Received February 26, 1926. * Contribution No. 89 from t h e Oil a n d Gas L a b o r a t o r > , M I. T. 4
6 6
Now Mrs. Charles McK. Welling. Trans A m . SOC.M e c h . Eng , 32, 834 (1910) THIS JOURNAL, 14, 683 (1922) Bur Mines Bull. 192.
excellent quality, the lard oil being-“prime.” All were practically free from acid. The porpoise-jaw oil had the folloming characteristics: iodine value 28 (Hanus), acid value 2.9 mg. KOH. The writers regret their inability to furnish further data about these oils. They were not determined. as the need of them was not evident. The names of some of the petroleum oils can be furnished to interested investigators. Results I n Table I it will be noticed that castor oil and lard show less spread than petroleum oils of the same viscosity. These organic oils when fresh and unoxidized are known to be better lubricants than the petroleum oils. The same holds true of the two petroleum oils compared with glycerol. I n Table I1 we see a similar condition of affairs. Sperm, an excellent lubricant, shows less spread than a mineral spindle oil. Porpoise jaw, lard, and rapeseed, of the same viscosity, show the same property. Reverting to Table I, the Red Engine oil and the “ M o ” oils seem to be distinctly better in their respective classes and the “cheap light oil” nearly as good as lard. Table I-Spread
of Different Oils a t 2 5 O C. and 70 R. P. M . with No. 22 Wire
OIL
Castor Pennsylvania oil of same viscosity
Viscosity Saybolt a t 100’ F. ( 3 8 0 C.) Seconds hfacM. 1485 124 185
Asphaltic-base oil (Be) Glycerol of same viscositya
516
Paraffin-base oil (bfo) Glycerol of same viscosity
604
36 43
Centiposes
18.1
Diff. 5,4
-1.3
1.0
21.3
5.3
24 28.5
3.7
3.0
0.7
Lard 214 Asphaltic-base oil of same viscosity ( T e )
11
1s
1.4 2.3
0.9
233
16 24
2.0 3.1
0.11
Asphaltic-base oil (Te medium), said t o be poor 285 Oil (Mo) above
56 24
7.1 3.1
4.0
13.5 11
1.7 1.4
0.3
Red engine oil heavy (said t o be poor) Oil ( h l o ) above
“Cheap light oil” (said to be poor) Lard
20s 214
Cal medium 381 55 o Glycerol was used here, as no oil of t h e same viscosity was ohtainable; glycerol is a notoriously poor lubricant.
Table 11-Spread
of Different Oils a t 25‘ C. and 70 R. P. M. with No. 26 Wire Viscositv Saybol; a t 100’ F.
(38” C )
OIL
Winter sperm Spindle same viscosity
Seconds 104
Porpoise jaw Pa spindle same viscosity
101
Lard Asphaltic-hase oil (Te) Same viscosity
214
Rapeseed Asphaltic-base oil ( T e above)
247
O
CentiM a c M . poises 18.5 0.55 0.93 34
23 34
0.65 0.95
0.30
I.GO
1.70
57 118.5
3.30
57.5
1.61 3 30
118.5
Diff 0.40
1.6’3
The writers fully realize that from so few experiments weighty conclusions cannot be drawn; however, they confirm Perrott’s work with gas blacks, and are interesting. They are now given out simply as a tentative method in the hope that the method may be tried by those interested, and found of use.
