967
V O L U M E 28, N O . 6, J U N E 1 9 5 6 of the chemical and spectrographic methods in cases where *ampling difficulties are minimized; tivo additional samples xere excluded from the table because they were inhomogeneous, as revealed by the greater spread of duplicate chemical determinations as well as the lack of agreement betn-een chemical and spectrographic results. The discrepancy b e k e e n chemical and spectrographic results for these tiyo samples was of the order of lv, absolute. Spectrographic analysis was particularly useful for detecting segregation, because i t utilizes a small area. S’ariations of as much as 25% of the amount present have been detected along the length of an %inch bar. However, in a few cases similar variations have been found in adjacent areas about 0.5 inch apai t. Another advantage of the spectrographic procedure is the speed with which the analysis may be accomplished. One analyst may complete with ease in one day about 25 samples exposed in triplicate. The small time between receipt of the sample and completion of the analysis is of considerable help
in a research program where the next step may depend upon the analysis of the previous melts. ACKNOW’LEDGBIENT
The author is indebted to Jerome E. Baird, Metallurgy Division, for the preparation of the spectrographic standards, to James K. Brody, Chemistry Division, for his helpful assistance in various phases of this xork, and to Ralph E. Telford, Chemistry Division, for excellent chemical work on t,he standard alloys. LITERATURE CITED
(1) Churchill, J. R., ISD. ESG. CHEM.,ANAL.ED. 16, 653 (1944). (2) Kiess, C. C., Humphreys, C . J., Laun. D. D., J . Research S a t ! . Bur. Standards 37, 2 (1946). (3) Pierce, W. C., Kachtrieb, K,H., ISD. ENG.C H m r . , A N A L . ED. 13, 777 (1941). (4) Tomkins, F. S., Fred, AI., J . Opt. SOC.Amer., 39, 357 (1949).
RECEIVEDfor review .4ugust 3 , 1955.
Accepted March 15, 1430.
Detection and Determination of Contamination of Aviation Gasoline by Heavier Fuels JOHN A. KRYNITSKY and WILLIAM D. GARRETT N a v a l Research Laboratory, Washington 25,
D. C.
To satisfy a military need, a simple test suited for field use has been developed and standardized for the detection and determination of small quantities of heavier fuels in aviation gasoline. This method is based on the fact that the height to which a contaminated gasoline will wet a calibrated paper under controlled experimental conditions is governed largely by the character and quantity of the heavy component present. The effect of the heavier fuel generally is to increase this wetting height. As the response is somewhat semilogarithmic in nature, it is most sensitive in differentiating between the lower levels-e.g., 0, 0.5, and lc/c JP-S-of contamination.
these conditions, the height to which the paper is wetted in a given time (creep height) is governed largely by the quantity and volatility of the heavy components in the gasoline. This “creep height” is easily indicated by the incorporation of a suitable oil-soluble dye into the gasoline sample. Preliminary experiments were encouraging, EO it was decided to develop this technique into a standardized test method. APPARATUS
The equipment developed for this work is shown i n Figures 1 and 2.
B
ECAUSE of the increased use of various types of aviation fuels, a need has arisen for a simple field method of detecting the contamination of premium gasolines by small amounts of heavier jet fuels. At least four different approaches had been considered: evaporative residue techniques ( I ) , distillation, selective solubility in alcohol of a topped concentrate, and tagging the heavy fuel by fluorescent or possible radioactive tracers ( 3 ) . The first method is unsuited for field use and the second lacks sufficient quantitative sensitivity. The third method is objectionable because preliminary experiments showed it to be highly dependent on the base fuel stocks. The last approach is potentially practical; however, it would require further additives in the heavy fuels and considerable work on the development of a suitable detecting instrument for field use. From all considerations, i t was deemed most desirable that the test should be based on the inherent existing differences in physical or chemiral properties of the individual fuels. Curtis R. Singleterry of this laboratory suggested a novel technique, which appeared to offer a most promising approach. In essence this method involves the suspension of the lover portion of a strip of filter paper in the gasoline and the passing of an air stream over the exposed paper surface. The gasoline rises up the paper by capillary action and is evaporated. Under
_ _
I
Figure 1. Test apparatus
The test box has a 100-cubic-feet-per-minute exhaust blower located on one end to provide the proper air velocity. The aluminum funnel in the after portion and the staggered caning a t the inlet are incorporated to smooth out the air pattern. The dial thermometer and accompanying wick are used to obtain the necessary wet- and dry-bulb temperature readings. The circular
!368
ANALYTICAL CHEMISTRY
rn
recess in the bottom of the box serves to position the test paper assembly. The test can be viewed at all times through the Plexiglas door.
PAPER HOLDER-
GENERAL PROCEDURE
To carry out a test, 60 ml. of fuel are placed in the jar togetlicr with 10 drops of the indicator dye. The brass top is fastened in place and the paper suspended so that the ruled immersion line coincides with the upper surface of the top. This assembly is then allowed to stand in the test box for 1 hour with the exhaust blower running. The test paper is withdrawn and the distance between the height to which the dyed sample had crept and the reference immersion line is measured.
.
BRASS TOP
TEST J A R
STUDY OF VARIABLES
I=- 1.4 T E S T PAPER
Inasmuch as the experimental part of this work involved the performing of well over 1000 tests, only limited and condensrd portions of the data which illustrate the various phases are described. Because many different fuel sources were used throughout these studies, each material was given a code designation. I n presenting the data, the designation of the fuel used is indicated in parentheses after the fuel type.
PAPER ASSEMBLY
SlOE VIEW
TOP VIEW'
Indicator Dye. Five oil-soluble dyes were tried: Sudan Blue (General Aniline & Film Corp.), oil yellow PHW (Calco), oil green No. 2 (Geigy), oil orange KO.4 (Geigy), and oil-soluble r e d 4 (Calco). Although all these dyes were satisfactory. oil orange KO.4 was judged to be superior because i t produced the clearest demarcation line and the best contrast. The indicator dye was added to the test fuel in the form of a 570 benzene solution; 10 drops were uscd per GO ml. of gasoline. The addition of the benzene was found to have no effect on the test.
BRASS TOP
Figure 2.
60
Teat paper assembly
0
A\i C A S A A J G A S A t 0 5 5 JP-SI11 0 A'/ GAS A tl 0% JP-5(1)
-
X
Test Time. Four periods of t h e were tested: 15 minutes, 30 minutes, 1 hour, and 2 hours. The shortest time yielded erratic results and failed to distinguish clearly between the various test fuels. Resolution was obtained a t 30 minutes and improved with the longer times. The 1-hour test was considered to be the best compromise, as the longer period did not sufficiently improve the resolution to warrant the extra time.
p--O-
20
Table I. (Test conditions. Concn. Of JP-5(1) in Avgas A , % 0 0 . .j
1.0
Table 11.
-P A P E R
Effect of Shape of Test Paper
Tcmjwrature, 75' F. Relative humidity, 50qo. grade. JVhatman No. 1)
Paper
____
Crecp Height, Arm. Rectangular Shaped paper strip paper strip 17 20 1 24 32 7 30 42 2
Yariations between Rolls of 1-Inch Whatman No. 1 Paper
[Test conditions. Temperature, 7.5' E.- Relative humidity. 5 0 R . Test f u p l , avgas A O.oc/, JP-5(1)] A v . Creep AV. Standard nI,u S o . of Height, Dei-intion. Deviation'i, 1)eiign;ition Tests AIm. Mm. Mrn. 13 56 32.7 1.6 2.0 D 6 26 8 1.4 1.7 G 6 28.4 1.1 1.6 L 63 34.2 1.4 1.9 AI 6 30.2 1.8 2.3
+
Paper Shape. I n the early studies, rectangular 1 X 6 inch stripe of paper were used. Although resolution was obtained, the creep height boundary was not well defined and the values obtained for different degrees of contamination were somewhat closer than desired. It was reasoned that a clearer boundary and better resolution might be produced by using a shaped
i
0
100
Figure 3.
200 AIR VELOCITY lFT./HIN)
300
0
Effect of air velocity on creep height
paper having a long narrow evaporating surface fed by a r i d e wick. This requirement was fulfilled by stamping out uniform test strips with a standard bone-shaped die ( 2 ) . Experiments comparing the shaped papers with the rectangular strips proved the reasoning to be correct (Table I). Except for this study, all work was carried out using shaped papers conforming to the dimensions indicated in Figure 2. Paper Texture, Standardization, Repeatability. .4s it was obvious that a highly uniform paper was necessary, only the three specially selected Whatman papers (grades 1, 3, and 4), intended for chromatographic use, were tried. Experimental test strips were cut from all those grades using the three forms available (1-inch-wide rolls, ll/&ch-wide rolls, and 181/2 X 221/2 inch sheets). Tests showed that the most satisfactory and reproducible papers were obtained from the I-inch-wide Whatman N o . 1 rolls. Although any particular roll of this paper appeared to be rather uniform, variations between rolls were noted. Each roll used was checked and standardized by running tests under identical conditions on papers cut from various parts of the roll. Typical results showing the variation between rolls are presented
V O L U M E 28, NO. 6, J U N E 1 9 5 6
969
in Table 11. The data show that the method has good repeatability. Thus, for the standard 0.5% contaminated aviation gasoline (avgas), the 56 papers tested from roll B yielded an average creep height of 32.7 mm. with an average deviation of 1.6 mm. and a standard deviation of only 2.0 mm. Approximately 1000 shaped test papers could be cut from a 600-foot roll of 1-inch Whatman No. 1 paper. Unless noted otherwise, test papers used throughout this work were cut from roll B. Air Velocity. To establish optimum conditions, tests were run in the apparatus using various exhaust blowers and blower speeds. I t was desirable to standardize on a speed within the region where the creep height i s independent of air velocity (between 200 and 400 feet per minute, a3 shoivn by the curves of Figure 3). Except for this study, the standard air velocity used was approximately 280 feet per minute. Air Direction. I n the standardized test, the sample bottle and paper assembly are placed within the apparatus, so that the test paper directly faces the air stream. Although this procedure was followed, experiments in n hich the test assembly n a s purposelv
rotated as much as 30' from the prescribed position showed little, if any, effect on the creep height. Sample Volume. With the devised apparatus, approximately 51 ml. of sample are required to bring the level in the test jar to the base of the test paper. Because approximately 3 ml. of aviation gasoline are evaporated in a typical test, the minimum sample which can be used is about 54 ml. The effect of the sample volume was determined by running similar tests using volumes of 55, 60, and 65 ml. For these, the distances from the liquid meniscuses to the upper edge of the slotted brass top TTere 21.4, 16.8, and 11.6 mm., respectively.
Table 111.
Effect of Sample Volume
[Test conditions. Temperature, 75' F. Relative humidity, 50%. Test fuel avgas A 0.5% JP-5(1)] Distance from Liquid Level Av. Creep Height Compared t o Creep Compared t o Sample Liquid t o Volume, Top of Slota, 60-All. Sample, Height, 60-hl1. Sample, 311. Mm. 1Im. Mm. Xfm. 55 21.4 -4.6 27.8 -4.9 60 16.8 32.7 +i'2 39.3 46:s 65 11.6
+
0
lleasured with cathetometer.
Table IV. Effect of JP-5 Concentration on Creep Height (Test conditions. Concn. of JP-S(I)in Avgas A, Yo 0 0.5 1.0 2.G 3.0 4.0 5.0
FUELS USED-AV GAS A JP-5(I)
From the data given in Table 111, it is seen that the creep height was influenced greatly by the liquid level. In view of this, it was apparent that valid results could be obtained only I)y adhering to a uniform sample size and using closely matchrd test jars
T E M F z 7 5 O E
RH
30
1
40
50
~50%
60
70
Two-ounce, wide-mouthed, Duraglas, green ointment jars were selected and screened by placing 60 ml. of distilled water in a jar, securing the brass top, and measuring the vertical distance between the liquid meniscus and the upper edge of the slot with a cathetometer. For a number of jars, this measurement was found to average 16.3 mm. Only jars which gave values within A 1 mm. of the average were selected. Of the batch screened, approximately 15% were rejected.
80
CREEP HEIGHT(HH3
Figure 4.
Temperature, 75O F. Relative humidity, 50%) Av. Creep 4v. x o . of Hpight, Deviation, Tests hlm. Mm. 12 20.1 1.4 56 1.6 32.7 12 42.2 1.0 4 58.1 2.1 65.5 4 1.2 69.5 4 1.2 4 72.9 0.9
Effect of JP-5 concentration on creep height
Sensitivity toward JP-5 Contamination. The sensitivity of the test to\\ a d detecting JP-5 contamination [JP-5 (jet propulsion fuel grade 5), one of the aircraft turbine and jet engine fuels specified under RIilitary Specification &TIL-F-5624B of 18 May, 19553 was established by running a number of samples of 115/145 avgas to which different amounts of JP-5 had been added. The results given in Table IV show that the presence of small quantities of JP-5 caused substantial changes in the creep height. Figure 4 shows that, for the papers used, a fairly good linear relation exists between the creep height and the log (7,contami0.5%). As this indicates that the sensitivity response nation is somewhat semilogarithmic in nature, it is evident that this test is best able to differentiate between the lower levels of contamination. Temperature. The effect of temperature was determined by running three different test solutions (avgas, avgas 0.57, JP-5, and avgas 1.07, JP-5) a t five different temperatures (60°, 70") 75O, 80°, and 90" F.). I n all cases the relative humidity was controlled a t 50%. The plot of the data presented in Figure 5 indicates that the creep height is inversely proportional to the
+
0
60
ao
TO
1E M PE R A1U RE
Figure 5.
(
90
'F,I
Effect of temperature on creep height
+
+
ANALYTICAL CHEMISTRY
970 temperature. From the shapes and roughly parallel relation of the curves it was possible to construct a correction table whereby creep heights obtained a t any temperature within the 60" to 00' F . range could be converted to a standard value. Humidity. This variable was evaluated a t several fixed temperatures by running tests under different conditions of relative humidity. Papers used in these studies were allowed to age for a t least 1 hour under the test conditions prior to use. Figure 6 presents a typical result of these studies. From this and other similar a o r k , it M-as evident that below 70yothe test is relatively insensitive to humidity. At the higher humidities, however, lower creep height values were observed. From a practical standpoint, it was considered that no serious error was introduced uhen the test was operated without using a correction a t humidities as high as 80%. Avgas and JP-5Sources. The response of the test toxard a wide variety of aviation gasolines and jet fuels was checked by measuring creep heights for: (1) uncontaminated 115/145 avgases obtained from different sources, (2) an aviation gasoline contaminated by nine different JP-5 tvpe fuels, and (3) various aviation gasolines contaminated by different JP-5's. Results of these tests are summarized in Figure 7. For each contamination level the obtained values fell within a band of creep heights about 7 to 12 mm. wide. The separation of bands for the 0, 0.5, and 1% contaminations, however, was great enough to prevent overlap. At the higher JP-5 concentrations, differentiation Mas not conclusive, as the limited data obtained showed some overlap. Heavy Contaminants Other than JP-5. Although the test nag
Table V.
Temperature 75O F. Relative humidity, 50%. Papers from roll VI) % Contamination 0.0 0.5 1.0 2.0 3 0 > 0 Contaminant .4verage Creep Height, h1ni.a
JP-5 Diesel fuel Viscount fuel b Viscount fuelc Viscount fueld Viscount fuel' Kerosine JP-1 JP-3 JP-4
Averages of three determinations each. b Viscount fuel, essentially a kerosine, obtained through courtesy of Capital Airlines. C Test conducted in 115/145 commercial avgas. d Test conducted in 100/130 commercial avgas. e Test conducted in 91/96 commercial avgas.
Table VI.
Temperature, 75' F.
Lubricant Hydrocarbon lubes Grade 1005 light turbojet Grade 1010 turbojet Grade 21 10 light engine Grade 9250 Diesel Grade 1080 aircraft engine Polyester oils Diamyl adipate Bis (2-ethy1hexyl)sebacate Bis(2-ethylhexyl) brassylate Tri(2-ethylhexy1)tricarballylate 0
Kinematic Viscosityat 68' F . , Cs.
20
50
40
30
70
60
80
90
RELATIVE HUMIDITY [PERCENT)
Figure 6.
Effect of relative humidity on creep height
w 0
0
IO
Figure 7.
20
30
40 50 60 CREEP HEIGHT(MM)
70
80
Creep height spreads for various JP-5aviation gas combinations
designed to detect and determine JP-5 in 115/145 avgas, experiments were run using other common fuel and lubricant-type materials. The results of the tests for ten fuels are summarized and compared with the behavior toward JP-5 in Table V. From this, it is evident that the responses t o Diesel fuel, Viscount fuel, kerosine, and JP-1 contamination are similar to that for JP-5; M hile JP-3, JP-4, Varsol, and motor gasoline give somewhat lower values. Contrary to first expectations, the test proved to be of no value for detecting the presence of either ethyl alcohol or navy special boiler fuel in aviation gasoline. The results for lubricating oils given in Table VI and plotted in Figure 8 prove that, for any given level of contamination, the creep height is an inverse funrtion of the viscosity of the non-
Relative humidity, 50%. Papers from roll VI) % Contamination 0 0 0.5 1.0 2.0 3.0, 5.0 Creep Height, Mm.
8 9 20.0 95,O 301.3 543.0
18.3 18.3 18.3 18.3 18.3
35.8 32.3 27.8 22.0 19.5
43.0 40.0 28.5 22.5 18.5
53.8 44.8
57.5
..
..
7.4 23.5 31.5 57.0
18.3 18.3 18.3 18.3
37.8 30.8 31.8 26.8
45.0 35.8 35.0 31.8
57.3 40.8 40.0 32.3
62.5 45.3 41.8 32.0
Averages of two determinations each.
I
0
Effect of Lubricating Oil Contaminants on Creep Height of Avgas B
(Test conditions.
1
0 '
TEMP.~75'f.
Effect of Heavy Fuel Contaminants on Creep Height of Avgas B
(Test conditions.
o .0gA V-G A"S -A t AV CAS A t 0 . 5 % JP-5(1)
Y Y
, . ..
, .
10.0
62.3 50.5 28.8 19.0 16.0
68.8 54.2 30.0 17.5 15.5
69.3 47.3 42.5
75.2 50.5 43.0
..
..
V O L U M E 28, NO. 6, J U N E 1 9 5 6
971
volatile contaminant, 4 s the viscosity of the heavy component increases, the creep height response curves tend to flatten. Contamination by oils of very high viscosities may result in either no change or even a slight lowering of the creep height as compared to that for the neat fuel. Gasolines Other than 115/145. A ~ I A T I OGRADE. X Because the distillation characteristics required 1)y specification MIL-F55i2-4 are identical for all grades of aviation gasoline, i t was of interest to compare the test response of the lower grades with that for tlie premium product. From t,he limited data obtained (Table 1-11), it is seen that for each level of contamination tested the tn.0 lower grades (91/96 and 100/150) yielded results within the limits expected for the 116/145 gasoline. COJIMERCIAL MOTORGASOLINE.To broaden the scope of this work, experiments \T-ere made using 17 different motor gasolines commrrcially sold in the Kashington, D. C., area. In running these, i t was necessary to cut the test time to 0.5 hour because the creep hrights a t 1 hour were in some cases above good reading limits. The results given in Table 1'111 show t\vo
Table VII.
Effects Using Aviation Gasolines of Yarious Grades
(Test conditions. Grade of Gasoline"
Temperature. 75' E. Relative humidit). , 50"~) Concentration of JP-5 b 0 5% 1 OF' Source " Creep Height, Rlm.
33.0 40.5 AA 19.0 37.0 47.0 AB 19.5 lB.O 33.0 43.5 100 :i130 B -1 32.5 42.5 BB 18.0 29.0-38.0 38.5-48.5 lld/14.5 .1 t o K 12.0-21.5 Sample rf 80 grade aviation gasoline was unavailable. 1, JP-5 froin source 1 used t o contaminate 91/96 and 100/130 grades. \-aliirs f o r 1 l.Vl4.i grade taken from Figure 7.
91,'9(i
Table VIII.
Creep Heights of ,\lotor Gasolines
( T r s t conditions. Temperature, 75O F. Relati\e humidity, 50Yc. Test time. 30 minutes)
Brand
Creep Heighta, 1 I m . Regular Premium gasoline gasoline 62.5 72.7 55.0 Gl.2 57,2 70.5 72.7 68.7 66.7 72.0 71.2
73.0 67.i
60
c
0
I
/"
05 I O
20
33
O I 0
50
LORE
OIL C O N C E Y T R A T I O N I P E R C E N I I
Figure 8. Effect of various lubricating oil contaminants on creep height of aviation gas B
7 8
I
70.0 69.7 . ~ T - P I . ~ $ of F two determinations. .%I..
GI
.a
58.i 70.2
...
63 0
interesting phenomena: Commercial motor gasoliries yield far higher creep heights than aviation grades, and, for most premium brands, the creep height is substantially lower than for the corresponding regular grades. Furthermore, an analysis of the data shoned that for these gasolines a definite relation exists between the creep heights and upper distillation characteristics. This is shomn in Figure 9, in which the creep heights are plotted against the evaporated distillation values [ l / 2 (end point temtemperature) 1. All values, except one, fall perature +OO'% within a straight narrov hand. 4 ? r ~ OXIDATIOK IUHIBITORS. Effect of Additives. CORROSIOS Studies using 20 corrosion inhibitor candidates and t v o oxidation inhibitors showed that none of these materials when present a t maximum or contemplated maximum allon able concentrations had any appreciable effect on the creep height of the gasoline used. IGXITIOSNODIFIERS. Results of v ork using tricresyl phosphate and tetraethyllead made it evident that neither of these materials has any substantial effect when present in concentrations up to those normally used. ACKNOWLEDGMENT
The authors are deeply indebted to C. R. Singleterry for invaluable technical assistance during the course of this work and to R. L. Shuler and C. A. McLean for their aid in performing many of the tests required. LITERATURE CITED
(1) Am. Sac. Testing Materials, ASTM Committee D-2 on Petroleum
4
50350
360
370
380
390
4 00
9 0 % TEMP+ END POINT TEMP. 2
Figure 9. Creep height vs. upper distillation characteristics of motor fuels
Products and Lubricants, Section A. Research Division V, of Technical Committee J on Aviation Fuels; under study. ( 2 ) ASTAI standard D 412-5lT, die B. (3) Johnson, J. E., Saval Research Lab., KRL Report 4182 (1053). RECEIVED for rei-iew January 23, 1956. Accepted March 22. 195l3. T h e opinions and assertions contained in this article are the private ones of the authors and are not t o be construed as reflecting tlie viervs of the N a v y DriJartment or t h e naval establishment a t large.
