INDUSTRIAL A N D ENGINEERING C H E M I S T R Y
January, 1924
25
Fluidity Anomalies in Refined Mineral Oils' By Eugene C. Bingham, William L. Hyden, and G. Raymond Hood LAFAYETTE COLLEGE, EASTON, PA.
I
T HAS been observed that when mineral oils are blended
the fluidity-volume concentration curves of the mixtures are not linear, as would be expected2 were the oils pure paraffin hydrocarbons. The cause of this anomaly is the more worthy of investigation because mineral oils are being used as standard substances for the calibration of viscometers. Two oils, known to the trade as Nujol and Mineral Seal Oil, were particularly suited for investigation because on mixing they give a linear specific volume-volume concentration curve, which makes unnecessary any correction3 on account of change in volume on mixing. The fluidities and densities were measured as already des ~ r i b e dthe , ~ materials not being subjected to any purification whatever. The fluidity-temperature curves obtained from the data given in Table I depart slightly from linearity, as would he expected. The fluidity-specific volume curves are all sagged, the pure Nujol the most of all. This is not what we ought to expect6 of pure hydrocarbons. The fluidityvolume concentration curves (Fig. 1) are considerably sagged, quite outside of any experimental error. In explaining this sag in the curves, it is noted that these oils are not pure compounds, but are complex mixtures containing considerable amounts of colloidal material. Since a sag in the fluidity curve may be caused by chemical reactions giving rise to large molecules6 or by a change in the condition or amount7 of the colloidal material present, it appears that the anomaly may be explained on the basis of a chemical reaction between some of the constituents or by the formation of colloidal complexes of increased number or size. The observations of Fulweiler and Jordans on the changes in fluidvty of an oil on standing suggested that Kujol would probably show anomalous changes in fluidity on treatment. The writers have therefore again measured its fluidity after two years) standing a t room temperature. They have subjected it to heat and to cold and have filtered it through activated fuller's earth. The viscometer used was the same throughout, and the temper:tture during the measurements was controlled t o 0.01" C. Corrections for any drainage error were made. Each observer obtained the constants of the viscometer separately. They were as follows:
thermometer, due to heating. The thermometer was removed from the bath during the heating. I n the spring of 1921 Mr. Hyden found the fluidity of Nujol to be 0.9243 a t 20" C. in closely agreeing determinations. I n December, 1922, Mr. Hood made six readings which agreed satisfactorily and obtained the value 0.9372. The instrument was cleaned out and refilled and four more measurements were made. The value obtained was 0.9366, which is essentially the same as before. There has therefore been an increase in the fluidity of 1.3 per cent in two years. By using different shearing stresses, it was proved that the oil did not possess a yield value greater than 0.8 dyne per sq. cm.; hence it must be regarded as negligible until measurements can be made with a still smaller experimental error. I n February, 1922, the fluidity of the Nujol which had been maintained a t room temperature was redetermined to be 0.9397, which is a further increase of 0.3 per cent. On heating this oil for several hours in the viscometer at the temperature of boiling water, the fluidity showed an immediate increase to 0.9435, or 0.4 per cent. This experiment was then repeated. The original fluidity was 0.9398 and the fluidity after heating and cooling back to 20" C. was 0.9430. All these values were the average of three or more, no one of which deviated from the mean more than 0.1 percent. 50
I 7
CONSTANTS OF VISCOMETERNo. 6 C
C'
hi
Hyden 7 . 9 5 4 - x 10-0 0.01296
0.08
Hood 7 . 9 5 3 x 10-1 0.01296 , 0.10
The radius of the capillary is 0.03202 cm., the length 13.75 em., and the volume of flow is 4.00 ml. No correction is necessary for hysteresis of the glass of the viscometerg or 1 Presented before the Division of Petroleum Chemistry at-the-65th Meeting of the American Chemical Society, New Haven, Conn., April 2 to 7, 1923. 2 Bingham, "Fluidity and Plasticity," p. 162. a I b i d . , p. 165. 4 I b i d . , p. 295. 5 I b i d . > p. 141. I b i d . , p. 113. 7 I b i d . , p. 293. THISJOURNAL, 14, 723 (1922). 0 Bingham, "Fluidity and Plasticity," p. 65.
*
MIN€RdL S E A L
NUJOL
FIG.1
If the increase in fluidity is due to a decrease in the size or number of the colloidal particles, it seemed probable that refrigerating the oil might cause a reversal of the process. This would not be the case, however, if the action going on in the oil was a process of chemical origin, such as oxidation. A sample of the oil was therefore kept a t a temperature of 5" C. for 40 days and the fluidity was then found to be 0.9381. As the fluidity immediately before chilling was 0.9398 and increasing steadily, and as the drop from 20" to 5" C. is less than one-fifth of the rise from 20" to 100" C . , this decrease in the fluidity is quite as much as we have a right to expect.
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
26
TABLEI-FLUIDITIESAND DENSITIES OF MIXTURES OB NUJOL AND MINERAL SEALOIL, Percentage Mineral Seal Oil
Temp.
C.
0 P
10
20 30 40 50 60 70 80
14.42 (a
0.8845 0.4564 0.8774 0.9243 0,8715 1.686 0.8652 2.889 0.8590 4.500 0,8527 6.613 0.8464 9.286 0.8402 12.52
P
24.19
c
0.8767 1.268 0.8694 1.836 0.8631 3.128 0.8564 4.900 0.8503 7.396 0.8430 10.14 0.8376 13.70 0.8312 17.79
P
40.27
c
0.8705 1.397 0.8640 2.484 0.8643 4.047 0.8508 6.167 0.8447 8.869 0.8384 12.21 0.831: 15.72 0.8253 20.88
P
0.8613 0.8543 0.8478 0.8412 0.8351 0;8288 0.8221
0.8150
54.99
c 2.464 4.115 6.301 9.165 12.70 16.91 21.68 27.18
In filtering the oil through activated fuller’s earth a 12.7-cm. (5-inch) column of the earth was used and the oil aspirated through the earth fifty times, the time of flow being about 5 minutes. Before filtration the fluidity was 0.9398 and afterward 0.9441, an increase of nearly 0.5 per cent. It is not assumed that this treatment has removed all the material capable of being removed by filtration, but it does prove that the process of filtration produces a marked change in fluidity. This investigation gives evidence that certain anomalies in mineral oils can be explained by the presence of colloidal material which presumably decreases the fluidity of the oil.
P 0.8226
0.8456 0.8391 0.8324 0.8263 0.8204 0.8133 0.8066
c 3.966 6.268 9.204 12.85 17.43 22.60 28.45 35.87
-
DIFFERENT TEMPERATURES
69.71
84.97
P
.(a
0.8444 0.8372 0.8310 0.8242 0.8181 0.8115 0.8046 0.7981
5.938 8.929 12.67 17.33 22.78 28.90 35.71 43.29
100
P
Q
P
lo
0.8362 0.8290 0.8226 0.8157 0.8091 0.8027 0.7959 0.7892
8.48 12.25 16.92 22.57 28.85 35.97 43.86 52.39
0.8290 0.8207 0.8140 0.8072 0.8006 0.7942 0.7875 0.7840
11.76 16.49 22.18 28.76 36.12 44.30 53.22 62.97
This colloidal material is less noticeable after the oil has been standing for a long time, or after the oil has been heated or filtered through fuller’s earth, but cooling the oil has the opposite effect. Lack of time prevented an investigation of the efficacy of powdered glass as a filtering medium. If colloidal material is adsorbed on glass, it seems possible that on the walls of the capillary it might cause the fluidity to appear to decrease with successive determinations. No such effect has, however, been observed. Thus, the fluidity of Nujol as measured in December, 1922, was 0.9370, 0.9373, 0.9379, and 0.9367.
Coal Products Chart By Alexander Lowy UNIVERSITY OF PITTSBURGH, PITTSBURGH, PA.
C o p y r i g h f 1923, by D Van Nostrand Company.
AT
Vol. 16, No. 1
The chad publishedby tbe D run Nostrand Cornpanu is printed in two rdors. B/a& tqpe infficates products direcfly obtuined from rodand fhe red type indicates products prepared by chemical methods
