82. The Effect Of Heat On Oils is very marked in all cases; some oils being much more subject to change than others, in viscosity and other properties, under the influence of an increase of temperature.
The lubricating power of an oil is decreased, while its tendency to spread is increased, with a rise of temperature. In order to ascertain the relative values of various oils in this respect the writer used a plate of glass 28 cm. x 40 cm., placed it flat on a table, and, depositing one drop of each oil near one of its longer edges, allowed it to remain in a temperature of 21° C. (= 70° F.) for 30 minutes. At the end of this time the glass plate was placed in a vertical position, with its edge near which the drops of oil had been deposited uppermost and horizontal. The time required by each oil to run down to the bottom, a distance of 25 cm., was noted. The width of the track, at a point 3 cm. from the location of the drop at the start, was measured when the oil had passed that point, and again measured at the same point when the oil had reached the bottom.
The same test was repeated, with all the conditions similar except that the temperature of the room was raised to 38° C. (= 100° F.) before the oil was placed on the glass; but the glass was allowed to remain in this temperature also for 30 minutes.
The results of both experiments are shown in table IX.
TABLE IX.
Relative Viscosity, Cohesion and Adhesion of Oils.
Temp. 21° C.(= 70° F.) and 38° C. (= 100° F.) Inclination Vertical.
| SYMBOLS ACCORDING TO TABLE III. | MINUTES REQUIRED TO FLOW 25 CM. AT A TEMPERATURE OF | WIDTH OF TRACK IN MM. AT A POINT 3 CM. BELOW STARTING PLACE WHEN THE OIL HAD FLOWED | ||||
| 21°C. =70°F. | 38°C. = 100°F. | Temp. 21°C (=70°F.) | Temp. 38°C. (=100°F.) | |||
| 3 CM. | 25 CM. | 3 CM. | 25 CM. | |||
| E. K. w. | 21 | 14 | 5 | 5 | 5 | 5 |
| W. F. N. w. | 18 | 12 | 5 | 5 | 5 | 5 |
| D. C. S. w. | 20 | 13 | 5 | 5 | 5 | 5 |
| D. C. S. ch. | 15 | 10 | 5 | 5 | 5 | 5 |
| D. C. S. cl. | 20 | 11 | 5 | 5 | 5 | 5 |
| W. C. w. | 13 | 8 | 5 | 1 | 5 | 1 |
| B. & K. w. | 13 | 11 | 5 | 0 | 5 | 0 |
| S. B. & Co. w. c. | 15 | 11 | 6 | 6 | 6 | 8 |
| C. L. Co. w. | 17 | 15 | 6 | 7 | 7 | 8 |
| C. L. Co. No. 1. | 15 | 10 | 6 | 6 | 5 | 5 |
| Glyc. | 14 | 10 | 6 | 6 | 5 | 8 |
| Alb. f. | 14 | 10 | 6 | 6 | 5 | 6 |
| Sp. | 10 | 7 | 6 | 1 | 5 | 0 |
| Ol. | 14 | 12 | 5 | 2 | 5 | 1 |
While the relative viscosity of oils in varying high temperatures is shown in table IX, the width of the track indicates the same properties as were explained in reference to table VII. Thus it is seen that the third and fifth columns of figures denote the relative adhesion of the oils, approximately according to the value of the figures; while the fourth and sixth columns exhibit their relative cohesion, and absence of adhesion, approximately according to the inverse value of the figures. Thus the tendency of the oil to spread, in the warm temperature to which time keeping mechanisms are frequently subjected, is indicated.
83. The Effect Of Cold On Oils is very observable in some varieties, converting them into greases, or even into hard, waxy solids. For out-of-door work unguents must be selected that will "feed" at any temperature to which they are exposed in the working of the bearings to which they are applied.