DISTILLATION/CETANE INDEX
OBJECTIVE
Acquire knowledge on performing PMCS, preparing the
laboratory apparatus, performing test procedures, reporting
results, and identifying environmental considerations for
ASTMs D-86 and D-976.
491-77L10
Lesson B-02
VGT 01
DISTILLATION/CETANE INDEX
Key Terminology
• Decomposition Point - the thermometer reading that
coincides with the first indications of thermal
decomposition of the liquid in the flask
• Dry Point - the thermometer reading that is observed at the
instant the last drop of liquid evaporates from the lowest
point in the flask
• End Point or Final Boiling Point - the maximum thermometer
reading obtained during the test
• Initial Boiling Point - the thermometer reading that is
observed at the instant that the first drop of condensate falls
from the lower end of the condenser tube
491-77L10
Lesson B-02
VGT 02
DISTILLATION/CETANE INDEX
Key Terminology
• Percent Evaporated - the sum of the percent recovered and
the percent loss
• Percent Loss - one hundred minus the percent total
recovery
• Percent Recovered - the volume in millilitres of condensate
observed in the receiving graduate, in connection with a
simultaneous thermometer reading
• Percent Recovery - the maximum percent recovered
• Percent Residue - the volume of residue in millilitres
491-77L10
Lesson B-02
VGT 03
DISTILLATION/CETANE INDEX
Key Terminology
• Percent Total Recovery - the combined percent recovery
and residue in the flask
• Thermometer Reading - the temperature of the saturated
vapor measured in the neck of the flask below the vapor
tube
491-77L10
Lesson B-02
VGT 04
DISTILLATION/CETANE INDEX
Preparation of Apparatus
Group 1
Group 1
Group 2
Group 3
Group 4
Flask, mL
100
125
125
125
125
ASTM Distillation Thermometer
7C (7F)
7C (7F)
7C (7F)
7C (7F)
8C (8F)
IP Distillation Thermometer
5C
5C
5C
5C
6C
Flask Support
A
B
B
C
C
32 (1.25)
38 (1.5)
38 (1.5)
50 (2.0)
50 (2.0)
0 TO 4.5
13 TO 18
13 TO 18
13 TO 18
Not above
32 TO 40
55 TO 65
55 TO 65
55 TO 65
ambient
Not above
Not above
Not above
Not above
ambient
ambient
ambient
ambient
C
0 to 4.5
13 to 18
13 to 18
13 to 18
13 to ambient
F
32 to 40
55 to 65
55 to 65
55 to 65
55 to ambient
Diameter of hole, mm (in.)
Temperature at start of Test:
Flask and thermometer, C
F
Flask support and shield
Graduated and 100 mL charge,
491-77L10
Lesson B-02
VGT 05
DISTILLATION/CETANE INDEX
Position of Thermometer in Distillation Flask
491-77L10
Lesson B-02
VGT 06
DISTILLATION/CETANE INDEX
Arithmetical Procedure
T = TL + (TH - TL)(R - RL)
RH - R L
where:
R = percent recovered corresponding to the prescribed
percent evaporated
RH = percent recovered adjacent to, and higher than R
RL = percent recovered adjacent to, and lower than R
T = thermometer reading at the prescribed percent
evaporated
TH = thermometer reading recorded at RH
TL = thermometer reading recorded ar RL
491-77L10
Lesson B-02
VGT 07
DISTILLATION/CETANE INDEX
Calculated Cetane Index Using Equations
Calculated Cetane Index = - 420.34 + 0.016 G2 + 0.192 G log M
+ 65.01 (log M)2 - 0.0001809 M2
or
Calculated Cetane Index = 454.74 - 1641.416 D + 774.74 D2
- 0.554 B + 97.803 (log B)2
Where:
G = API Gravity
M = mid-boiling temperature, degrees F
D = density at 15 degrees C, g/ml
B = mid-boiling point, degrees C
491-77L10
Lesson B-02
VGT 08
DISTILLATION/CETANE INDEX
Nomograph for Calculated Cetane Index
491-77L10
Lesson B-02
VGT 09
DISTILLATION/CETANE INDEX
SUMMARY
• Selecting and Preparing the Test Apparatus
• Performing the Test Procedure
• Reporting the Test Results
• Performing PMCS on Applicable Equipment
• Calculating the Cetane Index Using Equations
• Calculating the Cetane Index Values for Distillate Fuels by
Means of the Alignment Chart
491-77L10
Lesson B-02
VGT 10