ASTM D5236-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5236 − 18a D5236 − 23
Standard Test Method for
Distillation of Heavy Hydrocarbon Mixtures (Vacuum Potstill
Method)
This standard is issued under the fixed designation D5236; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method covers the procedure for distillation of heavy hydrocarbon mixtures having initial boiling points greater than
150 °C (300 °F), such as heavy crude oils, petroleum distillates, residues, and synthetic mixtures. It employs a potstill with a low
pressure drop entrainment separator operated under total takeoff conditions. Distillation conditions and equipment performance
criteria are specified and typical apparatus is illustrated.
1.2 This test method details the procedures for the production of distillate fractions of standardized quality in the gas oil and
lubricating oil range as well as the production of standard residue. In addition, it provides for the determination of standard
distillation curves to the highest atmospheric equivalent temperature possible by conventional distillation.
1.3 The maximum achievable atmospheric equivalent temperature (AET) is dependent upon the heat tolerance of the charge. For
most samples, a temperature up to 565 °C (1050 °F) can be attained. This maximum will be significantly lower for heat sensitive
samples (for example, heavy residues) and might be somewhat higher for nonheat sensitive samples.
1.4 The recommended distillation method for crude oils up to cutpoint 400 °C (752 °F) AET is Test Method D2892. This test
method can be used for heavy crude oils with initial boiling points greater than 150 °C (302 °F). However, distillation curves and
fraction qualities obtained by these methods are not comparable.
1.5 This test method contains the following annexes:
1.5.1 Annex A1—Test Method for Determination of Temperature Response Time,
1.5.2 Annex A2—Practice for Calibration of Sensors,
1.5.3 Annex A3—Test Method for Dehydration of a Wet Sample of Oil,
1.5.4 Annex A4—Practice for Conversion of Observed Vapor Temperature to Atmospheric Equivalent Temperature (AET), and
1.5.5 Annex A5—Test Method for Determination of Wettage.
1.6 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for
information only and are not considered standard.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.08 on Volatility.
Current edition approved July 1, 2018Nov. 1, 2023. Published July 2018November 2023. Originally approved in 1992. Last previous edition approved in 2018 as D5236
– 18. DOI: 10.1520/D5236-18A.– 18a. DOI: 10.1520/D5236-23.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5236 − 23
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific warnings, see 6.5.4.2, 6.5.6.3, 6.9.3, 9.5, 9.7, and A2.3.1.3.
1.8 WARNING—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious
medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use Caution
when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional
information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national
law. Users must determine legality of sales in their location.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D941 Test Method for Density and Relative Density (Specific Gravity) of Liquids by Lipkin Bicapillary Pycnometer (Withdrawn
1993)
D1217 Test Method for Density and Relative Density (Specific Gravity) of Liquids by Bingham Pycnometer
D1250 Guide for the Use of the Joint API and ASTM Adjunct for Temperature and Pressure Volume Correction Factors for
Generalized Crude Oils, Refined Products, and Lubricating Oils: API MPMS Chapter 11.1
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
D1480 Test Method for Density and Relative Density (Specific Gravity) of Viscous Materials by Bingham Pycnometer
D2892 Test Method for Distillation of Crude Petroleum (15-Theoretical Plate Column)
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D5002 Test Method for Density, Relative Density, and API Gravity of Crude Oils by Digital Density Analyzer
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 atmospheric equivalent temperature (AET), n—the temperature converted from the measured vapor temperature using
equations in Annex A4.
3.1.1.1 Discussion—
The AET is the expected vapor temperature if the distillation was performed at atmospheric pressure and there was no thermal
decomposition.
3.1.2 boil-up rate, n—the quantity of vapor entering the distillation head per unit time.
3.1.2.1 Discussion—
It is approximately equal to the takeoff rate, differing only by the parasitic heat losses. It is expressed in millilitres per hour for
a head of any given internal diameter or millilitres per hour per square centimetre of cross-sectional area of the throat for
comparative purposes.
3.1.3 condenser, n—the apparatus connected to the outlet of the distillation head in which condensation of the product occurs.
3.1.4 distillation flask, n—the flask, of glass or metal, in which the charge is boiled.
3.1.4.1 Discussion—
The flask is sometimes called a kettle or pot.
3.1.5 distillation head, n—the section immediately above the distillation flask containing the entrainment separator.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
D5236 − 23
3.1.6 distillation pressure (or operating pressure), n—the pressure measured in the distillation head just before the outlet to the
recovery system.
3.1.7 distillation temperature (or vapor temperature), n—the temperature of the vapors in the distillation head at the point of
measurement.
3.1.8 loading, n—the volume of charge relative to the cross-sectional area of the neck.
3.1.9 pressure drop, n—the difference between the operating pressure and the pressure measured in the distillation flask.
3.1.9.1 Discussion—
It is a result of the friction developed by driving the vapors through the system expressed in kilopascals (mm Hg).
3.1.10 spillover point, n—the lowest point in the head above the entrainment separator over which the vapors can flow to the
condensing region.
3.1.11 static hold-up (or wettage), n—the amount of liquid material remaining on the inside of the walls of the apparatus after the
distillation has been completed.
3.1.11.1 Discussion—
In this test method, it includes wettage of the distillation flask in the case of the steel flasks, but not in the case of glass flasks that
are removed for weighing after the distillation is completed.
3.1.12 takeoff rate, n—the quantity of product removed per unit time.
3.1.12.1 Discussion—
It is approximately equal to the boil-up rate differing only by parasitic heat losses.
4. Summary of Test Method
4.1 A weighed volume of sample is distilled at absolute pressures between 6.6 kPa and 0.013 kPa (50 mm Hg and 0.1 mm Hg)
at specified distillation rates. Cuts are taken at preselected temperatures. Records of vapor temperature, operating pressure, and
other variables are made at intervals, including at each cutpoint.
4.2 The mass of each fraction is obtained. Distillation yields by mass are calculated from the mass of each fraction relative to the
total mass recovery.
4.3 The density of each fraction is obtained. Distillation yields by volume are calculated from the volume computed for each
fraction at 15 °C (59 °F) relative to the total recovery.
4.4 Distillation curves of temperature versus mass or volume percent, or both, are drawn using the data from 4.2 and 4.3.
5. Significance and Use
5.1 This test method is one of a number of tests conducted on heavy hydrocarbon mixtures to characterize these materials for a
refiner or a purchaser. It provides an estimate of the yields of fractions of various boiling ranges.
5.2 The fractions made by this test method can be used alone or in combination with other fractions to produce samples for
analytical studies and quality evaluations.
5.3 Residues to be used in the manufacture of asphalt can also be made but may not always be suitable. The long heat soaking
that occurs in this test method may alter some of the properties.
NOTE 1—While the practice of reblending distillates with residue can be done to produce a lighter residue, it is not recommended because it produces
blends with irregular properties.
5.4 Details of cutpoints must be mutually agreed upon before the test begins.
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STILL HEAD DIMENSION CHART
Size A B C D E F G H I
25 mm 85 mm 75 mm 64 mm 47 mm ID 40 mm OD 4–5 mm 35/25 28/15 35 mm
36 mm 90 mm 75 mm 64 mm 68 mm ID 57 mm OD 5–6 mm 65/40 35/25 35 mm
50 mm 110 mm 100 mm 75 mm 94 mm ID 79 mm OD 7–9 mm 75/50 35/25 45 mm
70 mm 140 mm 100 mm 100 mm 131 mm ID 111 mm OD 10–11 mm 102/75 50/30 70 mm
FIG. 1 Distillation Head
5.5 This is a complex procedure involving many interacting variables. It is most important that at the time of first use of a new
apparatus, its components be checked as detailed in Annex A1 and Annex A2 and that the location of the vapor temperature sensor
be verified as detailed in 6.5.3 and Fig. 1.
6. Apparatus
6.1 Four sizes of apparatus, based upon the internal diameter of the distillation head (25 mm, 36 mm, 50 mm, and 70 mm), are
allowed. The apparatus (see Fig. 2) consists of a flask with heating mantles, an upper compensator, and a head containing an
entrainment separator. Attached to the head are the vapor temperature sensor, a connection for the vacuum gauge, a condenser, a
rundown line, a product receiver(s), and a vacuum pumping line with pump. The parts are connected by vacuum-tight joints to
facilitate servicing.
6.2 Distillation Flask:
6.2.1 The sizes specified for flasks are at least 50 % larger than the size of the charge to provide space for suppression of foam
and for bubble breaking. The size of the charge for each size of still is determined from the loading factor. The recommended
Cooke, Industrial and Engineering Chemistry, Vol 55, 1963, p. 36.
D5236 − 23
FIG. 2 Apparatus
loading factor is between 200 mL and 400 mL of charge per square centimetre of cross-sectional area in the neck of the head. Table
1 shows the range of charge volume that is recommended with each size of apparatus.
6.2.2 Flasks are made of borosilicate glass except those larger than 10 L, which are made of stainless steel for reasons of safety.
6.2.3 The flask is fitted with a thermowell reaching to within 6 mm of the bottom and offset from the center to avoid a stirring
bar. In the case of glass flasks, the bottom shall be slightly flattened or slightly concave, but not perfectly flat to facilitate the
rotation of the magnetic stirrer. Steel flasks can have a cooling coil for rapid quenching of the distillation in an emergency. Fig.
3 shows a typical example.
6.3 Stirring System—A magnetically driven stirring bar approximately 3 mm diameter and 20 mm long shall be provided for the
glass flasks, or 6 mm diameter by 50 mm long for the steel flasks. The edges shall be rounded to minimize grinding the wall of
the flask. The external magnetic drive must be capable of rotating the bar in the flask when located directly below and touching
the mantle. The drive can be used to support the apparatus above. An adjustable jacking mechanism is recommended for raising
and lowering the stirrer.
6.4 Heating System:
6.4.1 The flask shall be heated by means of a nickel-reinforced quartz fabric heating mantle on the lower half so that boiling rates
2 2
of up to 150 mL/h per cm of the cross-sectional area of the neck can be maintained. A heat density of 0.5 W/cm is adequate.
Usually two or more circuits are used to improve heat control by applying automatic heat to the bottom circuit.
6.4.2 A temperature sensor shall be located between the wall of the flask and the mantle for control of the skin temperature.
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TABLE 1 Standard Charge and Flask Size
Throat
Inside
Cross-Sectional Charge, L Flask, L
Diameter, mm
Area, cm
25 5 1–2 2–3
36 10 2–4 3–6
50 20 4–8 6–12
70 40 8–16 12–24
6.4.3 The upper half of the flask shall be covered with a mantle to compensate for heat losses. A heat density of 0.2 W ⁄cm is
adequate.
6.5 Distilling Head:
6.5.1 The head shall conform to the details shown in Fig. 1. It shall be made of borosilicate glass and be totally enclosed in a
silvered glass vacuum jacket having a permanent vacuum of less than 0.0001 kPa (0.00075 mm Hg).
6.5.2 The head shall be enclosed in a heat-insulating system such as a glass fabric mantle capable of maintaining the outer wall
of the glass vacuum jacket at a temperature 5 °C below the internal vapor temperature in the head. For this purpose, the vacuum
jacket shall have a temperature sensor fastened to the outer wall of the jacket at a point level with the vapor temperature sensor
and opposite to the outlet arm of the head.
6.5.3 The head shall be fitted with an adapter to support the vapor temperature sensor so that it is held centered in the neck with
the top of the sensing tip 3 mm 6 1 mm below the spillover point. This dimension can be checked by removing the temperature
sensor and inserting in its place a copper wire having a short right angle bend at the bottom. By feeling for the spillover point,
the distance from the top joint of the adaptor can be found. Laying the wire on the temperature sensor will then permit checking
of this dimension.
6.5.4 The vapor temperature sensor shall be either a platinum resistance thermometer, a thermocouple with the junction head fused
to the lower tip of the well, or any other device which meets the requirements in 6.5.4 and 6.5.4.1. It shall have a response time
of less than 60 s as described in Annex A1.
6.5.4.1 The vapor temperature measuring device shall have an accuracy of 0.5 °C or better and be measured with a resolution of
0.1 °C or better.
6.5.4.2 The vapor temperature measuring device shall be calibrated over the full range of useful temperatures in combination with
its associated instrument at the time of first use and at least once per year thereafter as described in A2.2.2. Alternatively, certified
sensors may be used, provided the calibration of the sensor and its associated recording instrument can be traced back to a primary
temperature standard. Recalibrate when either the sensor or the instrument is repaired or serviced. (Warning—Vapor temperature
measurement is one of the two major sources of error in distillation data.)
6.5.4.3 Verification of the calibration of the vapor temperature measuring devices is to be made on a regular basis. Verification
at least once a month is recommended. Verification of the calibration of the sensors can be accomplished potentiometrically by the
use of standard precision resistance or by distilling a pure compound with accurately known boiling point, as described in A2.2.3.
6.5.5 A head trap as illustrated in Fig. 4 shall be fitted to the adapter described in 6.5.3 for connection to the vacuum sensor. It
shall be kept filled with crushed dry ice at all times while in service.
6.5.6 A vacuum sensor shall be connected to the sidearm of the trap. The sensor shall be capable of reading the pressure with a
precision equal to or better than 0.00133 kPa (0.01 mm Hg), whichever is greater. A non-tilting McLeod gauge or other primary
reference device can achieve this accuracy when properly used, but a mercury manometer will permit this accuracy only down to
a pressure of about 1 kPa and then only when read with a good cathetometer (an instrument based on a telescope mounted on a
vernier scale to determine levels very accurately). Also, electronic sensors of the diaphragm type have been found satisfactory.
Vacuum gauges based on hot wires, radiation, or conductivity detectors are not recommended.
6.5.6.1 Primary standards, such as the non-tilting McLeod gauge, mercury manometer, or other analogous primary standard
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SYSTEM SIZE A B
25 mm 35/25 3 L
36 mm 65/40 6 L
50 mm 75/50 12 L
70 mm 102/75 24 L
FIG. 3 Distillation Flask
FIG. 4 Head Trap and Temperature Sensor
pressure devices, can be used without calibration when properly used and maintained. Alternatively, a tensimeter or certified
electronic sensors may be used, provided the calibration of the sensor and its associated recording instrument can be traced back
to a primary pressure standard.
D5236 − 23
CONDENSER DIMENSION CHART
System Size A B C D
25 mm 51 mm 28 mm 300 mm 35/25
36 mm 75 mm 45 mm 300 mm 65/40
50 mm 80 mm 54 mm 400 mm 75/50
70 mm 120 mm 80 mm 400 mm 102/75
FIG. 5 Condenser
6.5.6.2 Noncertified gauges shall be calibrated from a non-tilting McLeod gauge, another primary reference device, or a secondary
electronic standard traceable to a primary standard. A basic calibration procedure is described in A2.3. Recalibrate when either the
sensor or the instrument is repaired or serviced.
6.5.6.3 Verification of the calibration of pressure sensors is to be made on a regular basis. A frequency of at least once a week is
recommended. Verification of the calibration of the sensors can be accomplished using the procedures described in A2.3 or against
a certified reference system. (Warning—Measurement of vacuum (operating pressure) is one of the two major sources of error
in the distillation procedure. It is therefore of prime importance that the instructions on calibration and verification be followed
with great care and on a routine basis.)
6.6 Condenser—A condenser made of borosilicate glass shall be connected to the outlet arm of the head (see Fig. 5). It shall have
sufficient capacity to condense essentially all vapors and capable of operating at coolant temperatures up to 70 °C to prevent wax
buildup.
6.7 Pumping Line:
6.7.1 A pumping line shall be connected from the outlet of the condenser to the vacuum pump. The pumping line can be made
of heavy-walled rubber or light metal tubing, but its inside diameter must be greater than half the inside diameter of the outlet of
the condenser and less than 2 m long.
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INTERMEDIATE RECEIVER DIMENSION CHART
System Size A B C
25 mm 45 mm 120 mm 35/25
36 mm 51 mm 120 mm 35/25
50 mm 64 mm 150 mm 50/30
70 mm 75 mm 150 mm 50/30
FIG. 6 Receiver System
6.7.2 A surge tank of a size at least equal to the capacity of the flask shall be inserted in the pumping line adjacent to the pump.
6.7.3 An isolation valve of a diameter at least equal to the diameter of the pumping line shall be connected between the surge tank
and the vacuum pump.
6.7.4 A dewar-type trap made of borosilicate glass, such as that illustrated in Fig. 4, shall be placed between the top of the
distillation head and the vacuum sensor. It shall be kept filled with crushed dry ice at all times during the distillation to protect
the vacuum system from contamination with residual vapors.
6.8 Vacuum Source—A single-stage mechanical vacuum pump capable of maintaining a steady pressure in the system at all
operating pressures shall be connected to the pumping line. Automatic or manual control can be used.
6.9 Recovery System:
6.9.1 The recovery system is connected to the lower outlet of the product condenser and consists of a vacuum adapter to permit
removal of distillate receivers without disturbing the pressure in the system. A suitable manual device is illustrated in Fig. 6.
D5236 − 23
6.9.2 Alternatively, either automatic or manual devices can be used to collect part or all of the fractions within the system without
disturbing the operating pressure until the end of the run. Heating must be provided when needed to maintain the product in the
liquid state.
6.9.3 The product receivers shall be made of borosilicate glass and large enough for the size of the fractions to be collected. They
shall be calibrated to the nearest 1 % from the bottom. (Warning—This apparatus operates under high vacuum and high
temperature. It is recommended that these stills be kept in an enclosure to ensure that in case of an implosion, the operator and
others nearby are protected from flying debris, but that the front, at least, be transparent and removable for access to controls and
so forth. Automated stills, which are left unattended for long periods, should be equipped with an automatic fire extinguisher,
automatic quench, and alarm.)
7. Sampling
7.1 Obtain the sample for distillation in accordance with instructions given in Practice D4057 or Practice D4177. The sample can
also be a residue from Test Method D2892.
7.2 The sample must be in a closed container when received and show no evidence of leakage.
7.3 If the sample looks waxy or has solidified, warm it enough to liquefy it and ensure that it is thoroughly mixed before using.
7.4 If, upon examination, there is evidence of water in the sample, perform a preliminary distillation as described in Annex A3.
8. Preparation of Apparatus
8.1 Clean and dry all glass parts and assemble them with freshly lubricated joints as shown in Fig. 2. In the case of ball joints,
use only enough lubricant to produce a thin continuous film. An excess of lubricant can promote leakage. The rings of O-ring joints
should be made of Vitron-A, or silicone of equivalent hardness, and be lightly lubricated.
8.2 Tare the receivers to the nearest 0.1 % of the weight of the charge.
8.3 To check for leaks, pump the system down to a pressure of approximately 0.05 kPa (0.4 mm Hg) and isolate it from the vacuum
source. If, after 1 min, the rise in pressure is no greater than 0.01 kPa (0.075 mm Hg), the system is acceptable. If the rise in
pressure is greater than 0.01 kPa (0.075 mm Hg) in 1 min, the gauge and its connections must be examined and leaks corrected
before proceeding.
8.4 Calibrate the temperature and pressure sensors as described in Annex A2.
9. Procedure
9.1 Determine the density of the sample by one of the following test methods: Test Method D941, D1217, D1480, D5002, or
D1298. Refer to Guide D1250 to correct densities to 15 °C.
9.2 Insert the stirring bar.
9.3 From Table 1, determine the volume of the charge and calculate the mass to be charged by multiplying its density by the
desired volume.
9.4 Weigh this mass of charge into the flask to the nearest 0.1 %. In the case of flasks too large to handle, the flask can be put
in place and the charge drawn in from a container (weighed with its transfer line) using a pressure of 90 kPa to 95 kPa in the still.
The charge may need to be warmed to facilitate transfer. Its mass can be determined from the difference.
Vitron A is a registered trademark of DuPont E.I. De Nemours and Co., Wilmington, DE 19898.
D5236 − 23
TABLE 2 Operating Pressures and Distillation Rates
Operating Boil-Up
Take-Off Rate, mL/h
Pressure, Rate, mL/
25 mm 36 mm 50 mm 70 mm
kPa (mm Hg) (h·×·cm )
6.67 (50) 90–150 450–750 900–1500 1800–3000 3600–6000
1.33 (10) 75–125 375–625 750–1250 1500–2500 3000–5000
0.133 (1) 45–75 225–375 450–750 900–1500 1800–3000
0.0400 (0.3) 30–50 150–250 300–500 600–1000 1200–2000
0.0133 (0.1) 10–20 50–100 100–200 200–400 400–800
9.5 Attach the flask to the column (in the case of smaller flasks), and put on all the heating mantles. Put the stirring device in place
and turn it on. (Warning—Ensure that the safety shield is in place.)
9.6 A contiguous cutting scheme may be achieved in one of two ways, while remaining within the scope of the key aspects of
this method. It may be achieved by gradually reducing the pressure over the course of the distillation (dynamic) or done stepwise,
by slowing (or stopping) the takeoff rate to allow lowering of the operating pressure to achieve the final cut temperature. In each
case, this must be done keeping in mind the necessity to avoid starving the distillation (due to a slow takeoff rate), while at the
same time avoiding entrainment (by reducing too quickly the pressure applied to the system).
9.7 Apply heat to the flask at a rate that will raise the temperature of the charge quickly, but no faster than 300 °C ⁄h (540 °F ⁄h).
Do not exceed a skin temperature on the flask of 400 °C (750 °F) or cracking may result on the walls of the flask.
(Warning—Some hydrocarbon mixtures cannot tolerate 400 °C for any useful length of time. Reducing the skin temperature may
be necessary in these cases.)
9.8 Turn on the head compensation mantle and maintain the outer wall of the glass vacuum jacket at a temperature approximately
40 °C below the temperature of the liquid in the flask.
9.9 Reduce the pressure in the system gradually to a suitable starting pressure. Choose from Table 2 the highest pressure that is
consistent with the expected initial boiling point as well as the lowest pressure that is consistent with the maximum cutpoint, using
Fig. 7 as a guide. A pressure of 0.133 kPa (1.0 mm Hg) has been found satisfactory for starting a material having an initial boiling
point of 343 °C (650 °F) AET, such as residues from Test Method D2892 distillations.
NOTE 2—Degassing of the charge is sometimes evident before the actual distillation begins. This appears as bubbling at the surface without generation
of condensable vapors.
9.10 When distillation begins, evidenced by vapors entering the neck of the flask, reduce the heat input to a level that will maintain
the chosen distillation rate from Table 2 (see Note 2). Adjust the heat compensator on the head to maintain the outer wall of the
glass vacuum jacket at a temperature 5 °C below the vapor temperature.
NOTE 3—Although a range of distillation rates is permitted, 80 % of the maximum allowed is recommended.
9.11 In cases in which the observed initial vapor temperature will be 150 °C (302 °F) or lower, it is desirable to refrigerate the
first fraction receiver to ensure the retention of light ends. If solid, waxy material appears on the walls, warm the receiver with
an infrared heat lamp or hot air gun to liquify the product in the receiver in order to improve the accuracy of the reading. In
automatic operation, the receivers must be thermostated at a temperature high enough to ensure that no solidification takes place
and low enough to prevent evaporation of light material.
9.12 When using the dynamic method of pressure reduction, calculate a projected final cutpoint using the operating pressure and
the differential between the vapor and pot temperature as the operating envelope. Estimating that the difference between the vapor
and the pot temperature remain relatively constant, determine if the final vapor tempe
...