Viscosity of Petroleum Products Conversion of Kinematic Viscosity to Universal Saybolt Seconds' W. B. MCCLUERAND M. R. FENSKE,Pennsylvania State College, State College, Pa. HE conventional method of determining the viscosity
T
routine measurements of the viscosity of petroleum oils was of petroleum products in this country is by means of described. For the standardization of the Saybolt viscomethe Universal Saybolt viscometer (1). The Saybolt ter, oils of accepted Saybolt seconds viscosity are used and viscometer is considered satisfactory for plant control work corrections to the viscometer applied. The alpha oil standand for determining the specifications of commercial petro- ard of the American Petroleum InstituteZ is the principal leum products. On the other hand, this viscometer is not standard for checking the Saybolt viscometer. The work sufficiently accurate for many purposes (4) and requires in- here consisted of two parts. First, an accurate determinaconveniently large amounts of material for its use in research tion was made of the viscosity of alpha oil in stokes or work. Also, the resultant unit of viscosity, known as the poises in a single viscometer referred to water as a basis. Saybolt second, is entirely arbitrary and as such cannot be Although a careful viscometer design was necessary in order used in engineering design and physical measurements. to accomplish this, the method was chosen since more than Other types of viscometers are preferred for accurate casual attempts to obtain viscous pure organic liquids of viscosity measurements and for use in research work where suitable properties for viscometer standardization have not the quantity of processed material must be kept relatively resulted in success. Secondly, having established the vissmall. The results obtained by these improved viscometers cosity of alpha oil in fundamental viscosity units and havare expressed in fundamental units. These units are satis- ing used it also to standardize the Raybolt viscometers alfactory to the designing engineer but have no practical ready mentioned, the experimental relationship remained significance to those accustomed to express viscosity in to be determined between kinematic viscosity and Saybolt Saybolt seconds. Hence, there is a demand for accurate seconds over a wide viscosity range using a variety of oils. interconversion data in these units of viscosity both on the This was accomplished by measuring the viscosity of one part of the design engineers and on the part of the tech- hundred oils in each of two accurately calibrated, modified Ostwald viscometers (10) and in each of two Universal Saynologists of the petroleum industry. Equations have been proposed a t various times for con- bolt viscometers. DESIQNOF LARGEVISCOMETER.The viscometer used for verting fundamental units of viscosity to Saybolt seconds. m e a s u r i n g t h e viscosity of alpha oil directly Formulas of this nature are generally expressed against water is shown in Figure 1. In viscomein terms of kinemat,ic viscosity instead of abso-3.7-4 ters of this sort all errors or corrections arising lute viscosity since the densities of oils vary apbecause the experimental conditions do not cornpreciably. The effect of density on the reported pletely fulfill the conditions for Poiseuille's law viscosity of oils is similar in the case of Saybolt are expressible in terms of the length of capillary seconds and kinematic viscosity. Equations extube. Therefore, if this tube is made long, the pressing this relation are usually, therefore, given errors are immediately reduced in magnitude. in terms of kinematic viscosity. Certain errors or corrections mentioned below, Some of the interconversion equations proposed not normally of importance, would now become more recently are as follows: a p p r e c i a b l e i n covering a viscosity range of 1.88 KV = 0.00216 (8) - about one hundred fold as encountered here with s alpha oil and water, unless the viscometer were 1.80 purposely designed for this work. The small KV = 0.002115 (8) modified Ostwald viscometers would not be suit1.95 able. The nearest approach to a suitable visKV = 0.00226 (8) - s cometer for this purpose was that of Washburn and Williams (9). However, this viscometer when S is less than 100 and was never intended for this purpose, and the 1.35 design shown in Figure 1 is materially better. K V = 0.00220 (8)- 7 The best design data €or viscometers to be used over wide viscosity ranges have been inwhen S is greater than 100. dicated previously (IO)and are in agreement with In each of these equations, KV is kinematic the w o r k of G r u n e i s e n (6), Applebey (I), viscosity in stokes and S is Saybolt seconds. Washburn and Williams (9),and others. FollowFor any given kinematic viscosity, the results ing is a brief comment on the errors involved in obtained by using the equations may vary as the work here. much as 4 per cent. The need of a more accuKinetic Energy. While there is still disagreerate system of conversion based on a large amount ment ( 6 ) as to whether formulas or corrections of experimental data is evident. involving m@/g (where m is a constant, u the velocity of flow, and g the gravitational conEXPERIMENTAL WORK stant) constitute the best method for estimating errors due to kinetic energy, it appears In a previous paper (IO)the standardization of in viscometers (such as is shown in Figure 1, modified Ostwald viscomet.ers for the accurate FIGURE 1. IMPROVED 3 Obtained from the Atlantic Refining Company, Phila-
s
1
For the first paper in this series see literature citation
10.
VISCOMETER 82
delphia, Pa.
January, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY
83
where both the inlet and outlet of the capillary are in the calibrated by the Bureau of Standards were used, each readfluid) that the real error would involve the difference in two able to at least 0.01' C. (0.02' F.). I n addition, a check on of these quantities, one applied to the capillary inlet and the temperature was obtained by a ten-junction copper-cope1 other to the outlet. The results of Gruneisen ( 5 ) appear thermocouple readable to 0.01" C. that was calibrated by the more suitable and have been used by other investigators sodium sulfate transition point (32.383' C.), the ice point, with success. When Gruneisen's data for the large vis- and a known temperature of 20.0" C. One of the thermomecometer i n Figure 1 are used, with the highest rates of flow (R-ater a t 37.78' C.) the kinetic energy 8oo corrections, or end or turbulence effect?, are well below 0.1 per cent. Surface Tension. This factor may introduce an appreciable error when referring the v i s c o s i t y of oils t o w a t e r in the same viscometer. For the viscometer of Xashburn and Williams ( 9 ) this error might be about 0.45 per cent, provided both the oil and water wet the viscometer completely. For the viqcometer in Figure 1, since the capillary tube is much longer, the difference due to surface tension between mater and oil is about 0.08 per cent and nas t?~ neglected in this work. Drainage. This is the only principal error in- 8 volved in wing viscometers of this type since Ehe ' fluid drains incompletely from the upper bulb with a consequent variation in amount of fluid flowed through the capillary. For the viscometer uqed here, tl-e error might be 0.2 to 0.4 per cent. It was reduced in magnitude to negligible proportions by using another bulb made as nearly as posjible like the upper bulb on the v i s c o m e t e r , but with no capillary tube attached to it. The same oil was used in this bulb and allowed to drain a t the same temperature for the same time as the time of flow in the viscometer. It was then weighed and the drainage correction determined from the difference in this weight and the dry weight of the bulb. Relative Position of Bulbs. For the viscometer in Figure I , a ehift of 5 mm. a t the bottom, assuming the top pivoted, would introduce a n error of 0.1 per 20 40 WBU100 2w 400 6W8wlcocl 1Da7 4oooMoo cent. However, the dimensions of the wide arm are W e m a t S a v . Sewn& such that the d u m b bob used in it could a t most FIGURE 2. KINEM~TIC VISCOSITY US. UNIVERSAL SAYBOLT SECONDS s w i n g o n l y through about 2 mm. Since it was easy to align the viscometer vertically with the plumb bob to ters was also checked at the sodium sulfate transition point better than 2 mrn., the possible errors introduced in a!igning and agreed within 0.005O C., which is about the limit for the viscometer in the thermostat were negligible. reading the thermometer. All temperature measurements agreed within 0.01" C.; it is believed therefore that all temDIMENSIOKS OF VISCOMETER.The final dimensions chosen for the viscometer mere a capillary length of about 42 cm. peratures reported here are accurate to +=0.01' C. A conand a n inside diameter of about 0.065 cm. The diameter stancy of temperature of +=0.01' C. during a run was also atof the lower bulb, effective in the use of the viscometer, was tained; a Beckman thermometer served as a n additional about 4 cm. The upper bulb had a volume of approximately check. During a run, temperatures were tabulated a t 14 to 15 cc., and the volume of sample introduced into the definite time intervals, and the average was chosen as the viscometer for a measurement was 20 cc. The distance be- correct temperature. tween the two arins of the viscometer was about 3.7 cm. -4large Pyrex jar with a capacity of 42 liters served as The pipet for filling the viscometer was made in three the thermostat. It was filled with water that was stirred sections joined by ground-glass joints so that the pipet could with compressed air. be easily taken apart and weighed to determine the amount of TIME hIEdSUREhiESTS. From three to four timepieces sample introduced into the viscometer. -4variation of 0.5 were used in the runs with the large viscometer. These cc. in this volume would introduce a n error of only 0.1 per watches mere checked against each other and with a jeweler's cent. watch that checked with Arlington time signals. One of the The following apparatus and auxiliary equipment relates timepieces was a n electric stop clock, used primarily as a to the use of the large viscometer and the viscosity measure- check on the spring watches since no observations were made ments of alpha oil a t 20.0' C. (68.0' F.) and a t 37.78" C. on the frequency of the current. The spring watches were a (100.0" F.). Jaquet stop watch and a Meylan stop watch, both readable to TEMPERATCRE AM^^^^^^^^^^^. At about 38" C. (100 F.) 0.1 second. In addition, on the long time runs an accurate the viscosity of alpha oil changes approximately 0.3 per cent pocket watch was used. per 0.05" C. (0.1' F.) change in temperature. At 20" C. OPERATORS.Two operators independently observed the (68' F.) the change in viscosity is about 0.4 per cent per time of flow for each run. The results of the watches and 0.05" C. change in temperature. These facts require that operators were averaged to obtain the final value of time, the temperature be accurately known as well as maintained In general, the maximum deviation of any watch and any constant. Three thermometers which had been previously operator from this average time x a ? 0.2 per cent or less.
4
*8
'
O
84
1
N D U S T R I A L -4 N D E N G I N E E R I N G
TABLEI. KINEMATIC AND SAYBOLT VISCOSITY MEASUREMENTS AT 37.8' C. 1
2
3
4
5
1
2
3
4
VIS-
OIL KINEMATIC SAYBOLTCOSITT No. VISCOSITYVISCOSITYINDEX Centistokes Seconds 33.3 1 2.17 ... 36.3 3.21 2a 62 38.8 102 3.94 3a 42.1 103 5.10 40 42.3 50 5.11 107
DEYIATION
OIL No.
%
VIS-
KINEMATIC SAYBOLT COSITY VISCOSITY VISCOSITY [NDIX Centistokes Seconds 20.85 101.4 102 21.60 103.7 71 22.68 109.1 96 24.88 118.0 ... 24.91 118.8 99
0.0 f0.5 -0.3 +0.2 0.0
35 36" 37" 38 390
0.0 -0.2
-0.8
40a 415 42 43 440
25.14 30.20 31.38 31.52 32.56
120.7 141.9 147.2 146.9 153.8
102 78 103 107 99
CH E M AND
5 TION
9S.9" C. 1
DEVIA-
OIL NO.
7% -0.3
ISTR Y
68 69 70 71 72
OF
Vol. 27, No. 1
ONE HUXDRED OiLs
2
3
4
112.9 117.0 130.1 138.0
523.6 546.8 600.2 638.7
113 67 98 100
-0.9 -1.3 0.0 0.0
141.2 141.4 142.2 144.2 147.6
667.8 650.3 659.3 664.4 671.6
...
102 95 101 71
-2.4 +0.4 -0.4
-0.9
73" 74 75 76a 77
... .. .. .. ...
+0.5
-0.2 +0.4 -0.2
10Q
5.78 5.81 5.86 6.17 6.32
44.3 44.5 45.1 45.5 46.4
95 107 108 19 100
110. 12" 13a 14O 15a
6.77 7.47 7.89 8.57 10.24
48.0 49.6 51.5 53.1 59.3
43 95 93 15 101
-1.2 0.0 -0.9 +0.5 -0.3
45 46 47 48 49
35.36 38.59 40.39 40.67 47.62
165.7 178.7 188.3 188.9 220.6
101 107 95 108
-0.4 f0.5 -0.3 +0.2 0.0
78 79 80 81 82
166.8 176.4 185.6 189.0 192.7
777.0 821.7 864.9 879.2 895.1
16O
59.4 59., 60.0 60.8 61.4
6i
96 98 93 96
-0.3 0.0 -0.3 -0.4 -0.3
50a
17a 185 19" 2ou
10.25 10.43 10.46 10.65 10.83
51" 52 53 54
51,44 57.74 58.55 64.03 65.04
238.7 268.2 269. t 296.9 302.2
...
-0.3 -0.4 f0.4 -0.3 -0.5
83 a4 85 86 87
202.5 223.2 241.8 247.6 258.6
944.3 1041 1100 1143 1197
21a 22" 230 24 25a
11.34 12.17 12.78 13.03 13.15
63.5 65.6 68.6 68.8 70.7
103 71 -17 98 95
-0.g
-0.4 +0.7 -1.5
55 56' 57 58 59
65.12 66.48 73.05 78.17 78.67
302.5 312.1 338.5 363.0 370.9
-0.5 -1.6 -0.5 -0.7 -2.2
88 89 90 91 92
275.1 314.7 317.8 345.1 349.8
1259 1452 1466 1610 1624
-78 17
26a 27a 28a 29 30a
13.63 13.82 14.03 15.19 15.26
71.3 72.4 73.1 79.1 77.8
100 102 101 62 98
t0.4 -0.1 0.0 -2.0 0.0
60 61 62 63 64
90.48 92.01 96.00 96,70 99.30
416.0 424.8 443.2 446.3 463.t
101 98 96
...
fO. 1 -0.2 -0.2 -0.1 -1.3
93 94 95 96 97
383.5 408.9 530.2 610.2 801.1
1769 1882 2496 2852 3878
71 16 99 7s
477.9 479.0 483.7
96 93 103
-0.7 -0.2 -1.2
98 99 100
844.8 1178 1270
3993 5552 5924
6O 7" 8" 96
-1.1 0.0
+o.,
88.1 16 31n 17.72 -0.3 93.2 32" 18.96 -0.2 is 97.1 i8 330 20.15 +1.0 -0.2 99.9 20.55 100 345 5 Measurements a t 98 Sa C. (210' F)
65 66
67
102.9 103.6 103.6
SMALL VISCOMETERS.The calibration of these viscometers has been described previously (IO). They were used to measure the viscosity in centistokes of one hundred different oils whose Saybolt viscosities also were determined. Thus the experimental relationship between Saybolt seconds and kinematic viscosity was defined. Two accurately calibrated viscometers were used with each oil. A check on the viscosity of alpha oil as obtained in the large viscometer described above and the values obtained in ten different small viscometers showed the maximum deviation of any viscometer from the average of the ten to be 0.2 per cent, while the average of the ten checked the re*ult. on the large viscometer within the 0.2 per cent. UNIVERSALSAYBOLT ~ I s c o m x ' E R s . d new 3tandard instrument3 containing two tubes and certified by the Bureau of Standards as having zero correction was used. Each of the hundred oils was run in both tubes. The procedure wa. that of the American Society for Testing Materials (I). During the course of the work the tubes were checked a t frequent intervals with standardized oils. The primary basis, however, for standardizing the Saybolt viscometers was alpha oil having a viscosity of 295.0 Saybolt seconds. OILS.The hundred different oils used to define the relationship between kinematic viscosity and Saybolt seconds were from various sources and represent oils from a great variety of typical crudes. Viscosities were determined by each method a t 37-78' C. (100.0" F.) and a t 98.89' C. (210.0' F.). The oils varied in viscosity a t 210.0' F. from 37 to 682 Saybolt seconds, and a t 100.0" F. from 34 to 6049 Saybolt seconds. After the kinematic and Saybolt viscosities had been determined, the results were plotted on a large graph, approximately 2.2 X 2.7 meters in size. The abscissa was the logarithm of Saybolt seconds while the ordinate was the logarithm of kinematic viscosity expressed in centistokes The use of logarithmic coordinates expressed the results with a Purchased from the American Instrument Company, Wasliiiigtm. D C
100
... 95 93
...
19
... 43 ... 22
,..
5
VIS-
KINE~IATIC SAYBOLTCOSITY DEYIAVISCOSITY VISCOSITY INDEX TION Centistokes Seconds % 112.6 519.5 15 -0.3
-0.9 -0.1 -0.1
f0.5
f0.2 0.0
98
-0.8 -0.6 -0.6 -0.4 -0.3
101
-0.6 -0.7 f1.9 1-0.3 +o. 1
...
80 85 100
96 102 99
... ...
... ...
f1.4 4-0.6 f0.7 -0.4 fO. 1
f0.8 t l . 1 -0.7 f0.2 -0.5 -0.7 f0.4 4-1.7
constant percentage accuracy throughout the viscosity range investigated. On this large graph a distance of 1 mm. was equivalent to a deviation of about 0.2 per cent. DISCUSSION OF RESULTS
c.
VISCOSITY O F WATERAT 20.0" c. $t 20.0" (68.0' F.) there were twenty-two runs made on water using four different samples of water from two different lots, the measurements being made over a period of 17 days. One lot was a laboratory-distilled sample of water. The other was from a Barnstead triple all-tin distillation unit. The water from the latter unit averaged about 1.7 parts per million of solids, had a pH of 6.1 and an electrical conductivity of 1.4 X lo-* reciprocal ohms. The average time of flow for all these runs was 273.7 seconds; the maximum deviation of any run, any sample, any operator, and any watch from this average time was 0.2 per cent. The best runs check the average to 0.1 per cent. There were no corrections to be applied to the viscosity determinations on water for the viscometer shown in Figure 1. Since an error of 0.5 cc. in the sample of water introduced into the viscometer produced an error of only 0.1 per cent in the head, and the samples of water added to the viscometer a t 20.0' C. (68.0" F.) as well as a t 37.78' 0. (100.0' F.) were the same within 0.1 gram, these corrections were negligible. VISCOSITY OF WATER AT 37.78" C. At 37.78" C. (100.0" F.) there were twelve runs made on water using three different samples from the same two lots above. The measurements extended over 25 days. The average time of flow for all these runs was 188.0 seconds; the maximum deviation of any run, any sample, any operator, and any watch from this average time was 0.1 per cent. TEMPERATURE-V~SCOS~TY COEFF~CIEXT FOR WATER. Using 0.99820 and 0.99307 as the density of water a t 20.0" and 37.78' C., respectively, the ratio of the viscosity of water in centipoises a t 37.78" to centipoises a t 20.0" ir readily obtained by the relationship:
I N D U S T R I A L -4,?i D E
January 1935
S GI SE E R 1 5G
TABLEI:[, COSVERSIOX SAYBOLT VISCOSITY Seconds 30 40 50 60
io
80 90
7 -
1
0
.....
.....
4.36
4.69
7.88
7.58 10.49 13.24 15.81 18.23
10.77 13.50
16.05 18.47
4000 5000 6000
7000
8000 9000
10000
30
40
50
60
27 5 2 49.70 71.52 93.35 115.0 136.5 158.1 179.3
'9.79
.31.04
34 2 5
117.0 138.7 160.3 181,4 202.8
54.06 i5.87 97.66 119.2 140.8 162.4 183.6 205.0
100 237.3 450.5 662.0 8i3,2 1082 1286 1490 1695 1859 2103
PZ p =
19.42
3 10 6 32 0.33 12.14 14.80 17.28 15.66
20
47.50
69.25 91.21 112.8 134.4 156.0
177.2 198.5
51,s: 73.71 95. so
200.7
"00
300
400
500
258.8 471.6 683.1 894,2 1102 1306 1510 1714
280.0 492.7 704.2
301.5 513.6 725,3 936.5 1143 1347 1551 1755 1960 2164
?,?a. 0
1919 2123
915,s
1123 132i 1531 1735 1940 2144
PI = tidi _ _
where
2.77 6.00 9.04 11.86 14.53 17.04
25.22
175.1 196.4 0
18.70
2.44 5.67 8.75 11.59 14.28 16,79 19.19
2.07 5.34 8.46 11.32 14.01 16.56 18.94
10
153,s
215, 8 429.5 640.8 852.1 IO61 1265 1469 1674 1878 2082
1.70 5.02 8.18 11.05 13.76 16.30
td?
viscosity, centipoises
t = time of flow, seconds d = density of fluid
Using t'he values above, the ratio, p3,.7s/pL20.0 is 0.13833. It is surprising that there is such a wide disagreement for this ratio in the literature. Yet unless this ratio is known accurately, it is impossible to obtain any accurate absolute viscosity values a t various temperatures, since water is invariably used as the standardizing or reference fluid. One of the most accurate viscosity measurements (to 0.03 per cent) on water was that of Washburn and Williams (9). They measured the viscosit,y of water a t 18.0", 25.0', and 50.0' C. and also indicated the discrepancies for the ratio pt1/pt2 existing among several investigators. Washburn and Williams pointed out that their work checked closest' and very well the data of Hosking ( 7 ) . Hosking reported the viscosity of water a t 20.0" C. as 0.0100436 poise and a t 37.78" as 0.006850 poise, giving for the ratio p 3 7 . 7 8 / p 2 ~the . ~ value 0.68225. This checks the value found above to 0.15 per cent. The values of Binghani and Jackson (3) give for this ratio 0.68078, a difference of 0.38 per cent from the values found here. The data in the International Critical Tables (8) give for this ratio 0.6761, which differs by 1per cent from the values determined here. Since the value 0.6833 checks Hosking best and also the accurate work of Washburn and Williams, it will be used here as the basis for calculating the data a t 37.78' C. The value of 1.005 centipoises a t 20.0" C. is used as the absolute viscosity of water since this appears to be the most probable correct value. The viscosity of water a t 37.78" C. is then (1.005 X 0.6833 =) 0.6867 centipoise. VISCOSITYOF ALPHAO I L -4T 37.78" c. At 37.78' (100.0" F.) there were ten runs made on alpha oil using five different samples from one lot of oil; t.he measurements extended over 6 days. The maximum deviation of any run, any sample, any operator, and any match from the average time was 0.2 per cent Using the values outlined above for water, and correcting for variations in the sample added to the viscometer and for drainage from the upper bulb (total corrections of about 0.1 per cent), the viscosity of alpha oil a t 37.7s" C. is 63.91 centistokes. The density of alpha oil a t 37.78" i3 0.8923 and at 20.0 is 0.9025.
c.
S T K I:
85
O F \-lSCOSlTT UNITS
KIXEM.ATIC VISCOSITY IS CEXTISTOKEB 4 5 3 6
22.92 45.27 67.13 89.03 110.t 132.2
0
1000 2000 3000
2
C H E 31 I
534.9 746.5
957.4 1164 1368
1572 1776 1980
2185
56.23 (8.04 99.80
121.3 143.0 164.6
185.7
207.2 600
344.3 556.0 767.7 978 4 1184 1388 1592 1796 2000 2205
8
I
3.42
6.64 9.64 12.42 15.06 17.54 19.91 70
36.47
58.40 80.25 102.0 123.5 145.; 166.t 187.6 209.4
3.73 6.97 9.93
12.69
15.32 17.77
20.15
5ii.2
788.8 999.4 120.1. 1409 1611 1817 202 1 2?26
-
4.03
7.28
10.21 12.97 15.57 18.00 20,38
80
90
38.63 60.57 82.41 104.0 125.7 147.3
40.82 62.75 85.02 106.3
168.8
189.9 211.6 800
700 365 7
J
387.3 598.2 809.9 1020 1224 1429 1633 1837 204 1 2245
127.9 149.4 170.8
192.1 213.6 900 408.5 619.4 831.0 1041 1245 1449 1654 1858 2062 2266
YI~COSITY OF ALPHA i~ 20.0" C. The viscosity of alpha oil a t 20.0" C. (68.0' F.) was obtained by using another viscometer exactly like the one described in the foregoing except that the capillary tube was about 1 . 5 mm. in diameter. Thiq viscometer was standardized a t 37.78 O C. with alpha oil, and then the temperature was lowered to 20.0. There were eight runs made with two different samples of oil from the same lot used previously. The maximum deviation of any run, any sample, any operator, and any watch from the average was 0.27 per cent. This wider variation was probably due to temperature control since a t 20.0" C. a variation of 0.05" C. (0.1' F.) cawes a 0.4 per cent change in viscosity. The viscosity of alpha oil a t 20.0' C. is 191.25 centistokes. ViscosiTY MEASUREMENTS ON &HER OILS. Having established the foregoing standardization for water and alpha oil, the hundred other oil3 were measured in the small viscometers and standard Saybolt tubes as indicated. The experimental results are given in columns 2 and 3 of Table I. Column 2 is the measured kinematic viscosity and column 3 the Saybolt seconds. These data are represented logarithmically in Figure 2, which is a reproduction of the large graph mentioned previously. Column 4 gives the viscosity index of the oils and indicates the types of oils covered. In addition, column 5 gives the percentage deviation in the Saybolt viscosity from that obtained by converting the kinematic hiscosities to Saybolt seconds by Table 11, and the Saybolt seconds actually observed. After the data had been plotted on the large logarithmic graph, a curve was drawn through the established points. The average deviation of the data from the curve was approximately 0.5 per cent. Value3 were determined from the curve a t frequent intervals, and conversion tables, based on interpolation between the closely spaced determined values , were constructed. A tabular form of the conversion data was preferred to conversion formulas bince quadratic equations are cumbersome when a large number of conversions are made daily. This material is contained in Table 11. A cursory examination of these data on the basis of the relation in which constants A and B of the general equation K V = A S - -B
s
or
w e cr;iiii;rted by piotting I< i.,S YS. l/SLiiidicates that the converrrim cannot he representad by any simple single relation. Tliat is, when tlie experiinental d a h are evaluated and plotted iu ilie above manner, the data cannot be averaged aeenrateiy by a lineam rolation. llence it appears that either sweral ilntiilrntic equations over relatively narrow viscosity iunits or R single equation having exponents greater than 2 are necessary if the data are expressed laatliematically. The lollowing e i p t i o n , tiomever, has been found applicable for
KV
=
0.002042 S
+ 0.40
The data Riven in Table I aod represented in Figure 2 iudicate that the w n e conversion can be used for viscosities at either 3i.78" C. (l(H.0" F.) or 98.89" C. (210.0° FJ. It was anticipated that differences would be found, hut they wore not. evidenced by t,liedata obbnined. .ACKSUWLEDUMENT
The authors are indebted for the data presented to members of the laboratory staff,chid among wboin were M. R. Cannon, R. E. Hersh, J . I). Long, A. R. Rescorla, J. W. Johnson, xnd
J. 11.Pollack. This work was a part of the research program of tho Pennsylvania Grade Crude Oil Association, and this rriaterial is published with the permission of the School of Clieinirtry and Physics, Pennsylvania State College, and of tlie Association.
l (1)
r CITED ~
~
hinericm Society of Teeting Msterials. Standards. Part 11. p.
a n m;w.
~ ~M. P., i J . ~mem. b sot., ~ 97,2000 ~ .iiginj. ( 3 ) Binaham and Jnokson, in Iiatsohek's "Visoosity of Liquids." D. G S , Now York. D. Van Nostrand Co.. 1928. (4) Davis, G. 1% 13.. Lapoyrouse, hZ.,and Dean, E. W . , Oil Gos J., 30,No,46,92(19V2). (.SI Grunciuen, Wisr. Ahhand physik. fech. Heic/i8aanulrrlf, 4, 151 (2) ~
(1'305).
IG) Hatschok, "Viscosity 01 Liquids," p. 20, New York, D. Van NortrandCo., 1928. (7) Nosking, R., Phil. Mag., 18, 260 (1909); Science .Abstracts, 12, 503 (11~09). (8) Internstional Critiod Table?. Vol. 5 , p. 10, Now York, MoGmwHill Book Go.. 1928. 19) Waahburnand Williams, J. Am. Chem. Soc., 35,73711913). (IO) Willihngane. E. W.. McCluor. W. B. Fenske. M. R., snd MoGrew,R. V., Ieo. ENO.Cnmr., 4nal. Ed.,6.231 (1934). R ~ C ~ Y IFebruary ID 0. 1834:
This month we present our Erst iliustra. tion (No. 49 in the Bcrolzheimer Series of Alchemical and Historical Re roductions) by a Scottish artist. Sir Wi6iam Fettes Douglas w a born ~ in Edinburgh in 1822 and died in Newhurgh in 1891. From I877 until I882 he % a s Curator of the National Gallery of Scotland and later was President of the Royal Scottish Academy. Ile painted autodidactically. The original, which was painted in 1855, is in the Victoria and Albert M u s e u m in London, and has the richest coloring of any of the paintings in the series.
"But holy Alchimy of righte is to bee loved. which treateth of a pretious medicine, such as truly maketh golde and sylver fine."
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