Olson, Walter T

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MR June 1943
ADVISORY COMMITTEE FOR AERONA14~
WAIW’IME lUNBORT
ORIGINALLY ISSUED
June 1943 as
Memorandum Report
THE LOW -TEMPERATURE VOLUBILITY OF TECHNICAL
XYLIDINES IN AVIATION GASOLINE
By Walter T. Olson
Aircraft Engine Research Laboratory
Cleveland, Ohio
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WASHINGTON
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I3 117601354 1629
NiVCIONALADVISORY COMMITTEE FOR AERONAWICS
MmfoRANIuM REPORT
THE LOW-TEMPERATURE VOLUBILITY OF TliX3HNICAL
XYLIDINES IN AWATION GASOLINE
By Walter T. Olson
SUWY
Tests were made to determine the low-temperature volubility of
technical xylidines in aviation gasoline. The tests inciuded measuring
the cloud point, .orincipient“separationtemperature, at several con-
centrations of technical Xylidines in a 65-octane-number clear gasoline
without aromatics and with aromatics added in various percentages up
to 15 percent by volume and a grade 130, specification AN-F-28, emend.
‘ent 2} FJaSOline. Cloud points were determined as a function of con-
centration of xylidines in the gasolines described with an experimental
reproducibility of *1.5° C. The concentrations of xylidines that gave
a cloud point of -60° C as found by interpolation of the experimental
data were:
Concentrateon
of xylidines
(percent by weight),
3.7
5.0
7.3
Over 10
From the results it was
Fuel
—.
Extracted grade 65
Grade .55as delivered
IRtracted grade 65 containing
5 percent by volume of mixed
aromatics
Grade 65 containing 10 and
15 percent by volume of mixed
aromatics; grade 130
concluded that:
1. Technical xylidines in quantities LIp to 3.5 percent by weight
may be added to hydrocarbon fuels similar to those used in this inves-
tigation with no likelihood that separation will occur at -60° C.
2. The presence of aromatic hydrocarbons in the fuel increases
the volubility of xylidines.
2INTRODUCTION
The work reported herein covers the solulility of technical
xylidines in aviation ga~oline at low temperature~, especially at
-60° C, and is part of a series of tests to determine the suitability
of xylidines as an added antiknock component in aircrsft-engine fuel.
Specifically, cloud point, or incipient sepal*ationtemperature,
was determined for each of several concentrations of’technical
xylidines in gasoline. Several gasolines were selected for the te~ts,
both to determine the effect of aromatic ccntent on volubility of
xylidines and to represent typical military aircraft-engine fuel.
The investigationwas conducted at the National Advisory Committee
for Aeronautics, AircrafmtEngine Research Laboratory, Cleveland, Ohio,
during May 1943.
M+ARATUSANDTEST PROCETXJRE
Apparatus. - Figure 1 illustrates the apparatus used, A glass
gasoline sempie tube 30 by 2.5 centimeters was provided with a vent
and drying tube, an air-motorwdriven glass stirrer rctating in a
brass bushing, and a three-junction iron-const~i]tanthermopile in a
glass well. The gasoline sample ti.iDe was held in place with a stopper
in a 25 by 7 centimeter Dewar flask through which acetone as a coolant
was circulated by means of a centrifugal pump. The coolant was cir-
culated through approximatel~-35 feet of copper tubing coil in a
kerosene -dry ice refrigerating bath. The coolant temperature was
regulated by means of a valved bypass mound the refrigerating bath.
A thermometer in a well in the coolant line permttted observation of
the coolsnt temperature. The Dewar flask was supported in an insu-
lating box provided with windows. A small quantity of phosphorous
pentoxide placed in the bottom of’the insulating box as a drytng agent
prevented condensation of moisture on the walls of the glass Dewar
flask. The three-junction i.ron-constantanthermopile was used to
measure the gasoline sample temperature in the usual manner with dis-
tilled water ice as the reference temperature. Calibration of the
thermopil.ewas performed against a platinum resistance thermometer,
which had been calibrated “bythe National Bureau of Standards.
@n>les. - The analytical balance was used to make up test ssmples
of technical xylidines in the following gasolines:
1. Grade 65, specification AN-W-F-756, amendment 2.
2. Grade 65 with the aromatic hydrocarbons extracted.
33. Extracted grade 65 to which was added 5 percent by volume of
aromatic mixture consisting of five parts xylene, one part
,to,luene,and two parts.cumene.
4. Extracted grade 65 to which was,added 10 percent by volume .;
of an aromatic mixture consisting of five parts xylene,
one part toluene, and two parts cumene.
5. Grade 65 as delivered to which wae added 15 percent by volume
of an aromatic mixture cons~sting of five parts xylene, one
part toluene, and two parts cumene.
6. Grade 130, spectiication AN-F-28, amendment 2.
The grade 65 fuel as delivered was a clear gasoline and contained
4.5 percent aromatic hydrocarbons, approximately 60 percent of which
was benzene. The grade 130 fuel contained approximately 15 percent
aromatic hydrocarbons as well as tetraethyl lead, inhibitor, and dyes.
Table I lists the properties of the technical xylidines used.
Technical xylidines is a mixture comprising five of the six possible
xylidines.
TABLE I
PROPERTIES Or TECENICAL X’YZIDINFS
A.S.T.M. distillation, ‘C:
First drop
10 percent
30
50
70
90
End point
Specific g~avity, 25° C/!%”C
Refractive index, nD, at 25° C
Flash point (open cup), ‘C
160
209
209.5
210
210
210
212
0.972
1.55s7
96
Procedure. - To measure the cloud point of a test solution, s.
30-milliliter sample was placed in the sample tube, stirred, and the
temperature was lowered by circulating coolant. The temperature of
the sample at which a visual cioud first appeared was recorded as
the cloud point. This temperature was quite definite for each sample
and was obtained exactly by approaching it from both lower and.higher
temperatures. Reproducibility of the test data from operator to
operator was better than +l.5° C.
IF
RFSUUTS AND DISCUSSION
Table 11 lists the cloud points of technical xylidines for various concentrations
in the several ~~asolinesindicated.
TABLE II
CLOUD POINT OF ‘TECHNICALXYLIDINES IN AVIATION GASOLINE
Concentrat_ion!Grade65 as\Grade 65 ‘GradQ 65
of xyl.idines delivcrcda extracted ext?acted
(percentby 1 (°C) (“c) plds 5 &er-
weight) I cent ~lxed
,Z.GF:;C+
I , ——
3 ---.------- -62.5 I--------.--
~ ----------- -SQ.5 ~------------
5 -50.0 -56.0 -------_.-.,-
6 -57.5 ---------- -----------
1: -54.5 , -53.,0 -60.5
i ----------- -----.---- -5s.5
L 8.5 -52.010 , -49.5 ----------~---:;;-;----47,0 , ..——.—
acontained 4..5percent aromatics.
bAramatic-?i*ee.
clMixedaromatics consisted of five parts m~l.ene,
Grade 130
as delivered
(“c)
------------j-- ---------- 1------------ I
------- ------ [ :>-.65 >-65 1
>435 f----...---..+ >-65 i
one part toluene, and two parts cumene.
—5
.
Table III lists the solubillty of technical xyiidines in the
various gasolines at -60° C as determined by interpolation of the
experimental cloud-point data.
.,
TABLE III
VOLUBILITY OF TE2HNICAL XYLIDINES AT -60° C
Xylidifies
Fue1 (perc~:ty
.—
Grade 65 extracted (aromatic-free)
—
3.7
Grade 65 as delivered (4.5 percent aromatics) 5.0
Grade 65 extracted plus 5 percent mixed 7.3
aromatics
Grade 65 extracted plus 10 ‘percentmixed >1~.o
aromatics
Grade 130 as delivered (approx. 15 percent >10.0
aromatics)
.—— —
aMixed aromatics consisted of five parts xylene, one part
toluene, and two parts cumene.
It is apparent that the volubility of technical xylidines in
gasoline increases with increasing content of aromatic hydrocarbons.
Furthermore, the greater volubility of xyl.idi.nesin “Uleextracted
grade 65 fuel plus 5 percent of the xylene-toluene-cumenemixture
than in the grade 65 fuel as delivered (4.5 percent aromatics, mostly
benzene) indica~es that the benzene homologies are more effective
solubiiit,yimprovers for x~lidines than is benzene alone.
Aircraft Engine Research Laboratory,
National Advisory Committee for Aeronautics,
Cleveland, Ohio, June 4, 1943.
T“””’”’1 A
B
:
E
F
G
H
I
J
(potentiometer
with
Qgaluononfeter
NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS
Coolant-thermometer uell
Insulotlng box I
Oiwss ond uolue
1
$omple tube
Three-junction Iron-constonton
thermoplte
~iye;iosk
Cold-junctfon both
Centrifugal clrculotlnf pump,
uorioble speed
Refriferoting both
Figure 1. - cloud-point opporotus.
llllll
3 117601354 1629


The low-temperature solubility of technical xylidine in aviation gasoline

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