This standard is published for the first time. This standard specifies the test method for the melting point and melting range of chemicals - capillary method. This standard is applicable to the determination of the melting point and melting range of chemicals, and is a general method for temperatures ranging from 300°C to above. This standard is equivalent to JISK0064:1992 "Method for determination of melting point and melting range of chemicals" (English version). GB/T 21781-2008 Test method for melting point and melting range of chemicals - capillary method GB/T21781-2008 Standard download decompression password: www.bzxz.net
This standard is published for the first time. This standard specifies the test method for the melting point and melting range of chemicals - capillary method. This standard is applicable to the determination of the melting point and melting range of chemicals, and is a general method for temperatures ranging from 300°C to above. This standard is equivalent to JISK0064:1992 "Method for determination of melting point and melting range of chemicals" (English version).
This standard is equivalent to JIS K0064:1992 "Methods for determination of melting point and melting range of chemicals" (English version).
This standard is proposed and managed by the National Technical Committee for Standardization of Dangerous Chemicals Management (SAC/TC251). The
drafting units of this standard: Guangdong Entry-Exit Inspection and Quarantine Bureau, Hubei Entry-Exit Inspection and Quarantine Bureau, Shenzhen Entry-Exit Inspection and Quarantine Bureau.
The main drafters of this standard: Liu Yingfeng, Zhai Cuiping, Zhou Minghui, Li Dan, Li Quanzhong, Zheng Jianguo, Cui Hairong, Guo Jian, Li Ying, Li Qingxiang.
This standard is published for the first time.

The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, the parties to the agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version shall apply to this standard.
GB/T514 Specifications for glass liquid thermometers for petroleum product testing
GB/T8170 Rules for numerical rounding
JISK0050 General principles for chemical analysis
JISK0211 Technical terms for analytical chemistry (general part)
JISR3503 Glassware for chemical analysis
Japanese Pharmacopoeia (12th revised edition)

ICS13.300
National Standard of the People's Republic of China
GB/T21781—2008
Test method for melting point and melting range of chemical products - Capillary tube method
Published on 2008-05-12
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Standardization Administration of China
Implementation on 2008-09-01
This standard is equivalent to JISK0064:1992 Test method for melting point and melting range of chemicals (English version). This standard is proposed and managed by the National Technical Committee for Standardization of Dangerous Chemicals (SAC/TC251). GB/T 21781—2008
The drafting units of this standard are: Guangdong Exit-Entry Inspection and Quarantine Bureau, Hubei Exit-Entry Inspection and Quarantine Bureau, Shenzhen Exit-Entry Inspection and Quarantine Bureau. The main drafters of this standard are: Liu Yingfeng, Cui Ping, Zhou Minghui, Li Dan, Li Quanzhong, Zheng Jianmu, Cui Hairong, Guo Jian, Li Ying, Li Qingxiang. This standard is published for the first time.
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1 Scope
Test method for melting point and melting range of chemicals Capillary method
This standard specifies the test method for melting point and melting range of chemicals - Capillary method: GB/T 21781—2008
This standard is used for the determination of melting point and melting range of chemicals, and is a method with a temperature range from above room temperature to 390°C. Note 1: Melting point is used for substances with a definite melting point. Note 2: For materials with a melting range (such as glass, amorphous bodies, or multi-component mixtures such as oils, waxes, etc.) without a definite melting point, Note 3: If the test method specified in the standards for other individual products or a series of products is not recommended by this standard, it is recommended to test according to the method in this standard.
Note 4: The method described in the standard is a general method and is applicable to chemicals with good safety. For some chemicals, due to their volatility, explosiveness or radioactivity, the safety of the test cannot be guaranteed and the standard is not applicable. ? Normative references
The clauses in the following documents become the clauses of this standard through reference in this standard. For all dated references, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, the customers who submit the documents to this standard are encouraged to study whether the latest versions of these documents can be used. For all undated references, the latest versions are applicable to this standard. GB/T5[4 Technical conditions for glass liquid thermometers for testing petroleum products GB/T8170 Rules for numerical rounding off
JIS KOO General rules for chemical analysis
JIS K0211 Technical terms for analytical chemistry (general part) JIS R3503 Glassware for chemical analysis Japanese Pharmacopoeia (12th revised edition)
3 Terms and definitions
Technical methods and definitions established in JIS K0050 and JIS K 021. apply to this standard. 4 General requirements
The general requirements for the determination methods in this standard shall comply with the requirements of JIS K0050. Glassware shall comply with the requirements of JIS R3503. The numerical rounding off shall comply with the requirements of the standard GB/T8170. 5 Test method for melting point
The method for determining the melting point can be carried out by any of the following methods: a) daily measurement method;
b) instrumental method.
5.1 Visual method
5. 1. 1 Principle of the method
Heat the sample in a glass capillary tube placed in a heat transfer liquid and observe the melting point by visual inspection. 5.1.2 Instruments and equipment
5.1.2.1 Melting point determination device
Fix the capillary tube containing the sample on the thermometer so that the part of the capillary tube containing the sample is close to the middle of the mercury ball of the hygrometer. Immerse the sample in the center of the heat transfer liquid in the heating device at a position 20m above the imaginary part, as shown in Figure 1: I
GB/T21781—2008
Heater III
Heat transfer liquid;
In addition,
Thermometer
Immersion line
Thermometer with immersion line;
Elastic body for fixing temperature;
Control the opening of the heat transfer liquid:
Coiled elastic body:
Capillary tube:
Elasticity for fixing the lid.
Hot liquid melting point
Figure 1 Example of melting point determination instrument (visual method)
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Unit: mm
GB/T21781—2008
You can also choose a measuring device that circulates the heat transfer liquid by stirring, as shown in Figure 2. This device requires that the bottom end of the capillary tube containing the sample is fixed as close as possible to the mercury ball of the thermometer, D
-Observation lamp
Lighting lamp:
Thermometer:
Liquid surface of heat transfer body:
Capillary tube:
Heater:
Temperature control sensor:
Heater:
Agitator:
J—-Heat transfer body:
-Cooling fan.
Figure 2 Example of melting point tester (visual method -
5.1.2.2 Heater
Made of first-grade hard glass, shape and size as shown in the table! 5.1.2.3 Heat transfer liquid
Use a container with a stirrer to circulate the heat transfer liquid)... Generally water or silicone oil. Silicone oil should be thermally stable above the measurement temperature, and the kinematic viscosity at 25°C should be between 50 mm2 /s~3
GB/T 21781—2008
100mm*/s.
5.1.2.4 Cover
Made of tetrafluoroethylene resin, rubber or cork. 5.1.2, 5 Thermometer
No.1 to No.6 thermometers with immersion wire (sticking type) specified in this Pharmacopoeia (12th revised edition). If the expected melting point is 7C℃ or lower, GI-54 and GB-55 thermometers specified in GB/T514 can be used. 5.1.2.6 Capillary
A tube made of hard glass. One end is closed, with an inner diameter of 0.8mm~1.2mm, a wall thickness of 0.2mm~0.3mm, and a length of about 150mm.
5.1.2.7 Heater
It can heat the liquid from 15℃ below the expected melting point to 5℃ above the expected melting point, and can control the heating rate of the heat transfer liquid to be about 3℃/min or 1℃/min.
5.1.2.8 Dryer
It contains glue as a detonator.
5.1.3 Sample pretreatment
Grind the sample into fine powder. If there is no special requirement, the sample should be dried in a desiccator for 21 hours. 5.1.4 Determination steps
5.1.4.1 Put the dried sample into a capillary tube with one end closed and stand it upright with the closed end at the bottom. Take another dry glass tube about 7 cm long and stand it upright on a glass or porcelain plate. Drop the capillary tube containing the sample into it several times until the sample in the capillary tube is compressed to a height of 3 mm.
5.1.4.2 Heat the heat transfer liquid and slowly raise the temperature to a temperature about 10°C lower than the expected point. 5.1.4.3 Adjust the liquid level of the heat transfer liquid to be consistent with the immersion line of the thermometer. 5.1.4.4 Set the capillary tube containing the sample as shown in Figure 1 or Figure 2. 5.1.4.5 Heat the heat transfer liquid at a rate of about 3°C/min. When the temperature rises to about 5°C below the expected melting point, reduce the heating rate to about 1C/min.
5.1.4.6 When there is no identifiable solid sample in the capillary (i.e., when it is completely liquefied), read the thermometer reading at this time (accurate to one tenth of the smallest scale), which is the melting point of the sample and is used as a measured value of the melting point. 5.1.4.7 Repeat steps 5.1.4.1 to 5.1.4.6 at least three times, take the average value, and round it to one decimal place to obtain the melting point. 5.2 Instrument method
5.2.1 Principle of the method
Heat the sample in the capillary and use an instrument to detect the current fluctuation caused by the phase change process or the change in transmittance during the phase change. Record the temperature at that time to determine the melting point.
This method is not applicable to the detection of optically opaque samples in the molten state. 5.2.2 Instruments and Equipment
5.2.2.1 Instruments
The measuring equipment used is shown in Figure 3. If necessary, the results obtained by using this device for substances with known melting points will be compared with those obtained according to 5.1 method to compare the values ​​measured, confirming that there is no difference between the two. 4
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Metal block (furnace):
Sample,
Light source:
Fan;
Temperature control sensor;
Data processing and recording protocol,
Light drive instrument:
Heater;
Energy capillary;
Edge arrow.
GB/T 21781—2008
, one by one, put the capillary into the metal block (furnace), heat it according to the preset heating rate, and the light beam emitted from the light source is projected to the sample through the light source: Determination principle
When the sample is melted, the light transmitted increases, which is detected by the light sensor and converted into voltage. The output data is sent to the recorder, which records the rate curve:
Figure 3 Example of automatic melting point determination instrument (instrument method) 5.2.2.2 Capillary
Made of hard glass, one end of the closed tube, the inner diameter is 0.8mm-~1.2mm, the wall thickness is 0.2mm-0.3mma, the length of the capillary depends on the instrument used, after installation, the exposed part should be 10mm~-20rl, 5.2.2.3 Dryer
Same as 5.1.2. 8.
5.2.3 Sample pretreatment
Same as 5.1.3,
5.2.4 Determination steps
5.2.4.1 Load the sample according to 5.1.4.1
5.2.4.2 Set the working conditions, heat the sample at a rate of about 1℃/min, and determine the melting point. 5.2.4.3 Repeat steps 5.2.4.1 to 5.2.4.2 at least three times, take the flat groove value, and round it to one decimal place to obtain the melting point, GB/T 21781—2008
6 Test method for melting range
6.1 Principle of the method
The melting range refers to the temperature range from the sintering point to the full melting point. 6.2 Instruments and equipment
Same as 5.1.2.
6.3 Sample pretreatment
Same as 5.1.3.
6.4 Determination procedure
After installing the sample according to 5.1.1.1, perform the determination according to the following steps. 6.4.1 Heat the heat transfer liquid and slowly raise its temperature to about 10°C below the expected melting temperature. 6.4.2 Adjust the liquid level of the heat transfer liquid to be consistent with the immersion line of the thermometer. Insert the capillary tube filled with the sample and fix it so that the part of the capillary tube containing the sample is in close contact with the top of the mercury bulb of the thermometer. 6.4.3 Heat the heat transfer liquid at a rate of about 3°C/min. When the temperature rises to about 5°C below the expected humidity, reduce the heating rate to about 1°C/min.
6.4.4 Observe the sample carefully and read the sintering point temperature (through the wetting point) to one tenth of the smallest scale. Measure the sintering point temperature. 6.4.5 Continue to observe the total melting point, passing through the collapse point and the half-moon point, and read the temperature of the total melting point, accurate to one tenth of the smallest scale, to obtain the measured value.
6.4.6 Repeat the steps from filling the sample to 6.4.5 at least three times, take the average value, and obtain the sintering point and the total melting point. The temperature range from the sintering point to the total melting point is the melting range of the measured compound. Note: When the sample is heated, the following five changes will be observed (see 4): a) The wetting point is the stage where uniform small droplets are formed on the surface of the companion product and the glass wall. The stage when the sample begins to adhere and a gap is formed between the inner wall of the glass and the sample. b) The sintering point
The stage where the sample begins to collapse and melt to the bottom of the capillary. e) The collapse point
The half-moon point
The stage where the collapsed sample is partially dissolved in the body and a complete half-moon is formed above the liquid. Stages of complete liquefaction of solid products
a) Wetting point b) Sintering point e) Collapse point d) Half-moon point e) Complete melting point Figure 4 Changes of samples when heated
7 Precautions for handling chemicals
When handling chemicals, first determine the product's terminology and safety characteristics. If the product's safety cannot be determined due to insufficient details of its physical properties, first investigate and study it, and then operate it after having a sufficient safety plan. When handling toxic, harmful, and radioactive chemicals that are legally restricted, you should follow the relevant laws and regulations and only operate after providing sufficient preparation and planning.
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GB/T 21781-2008
People's Republic of China
National Standard
Test method for melting point and melting range of chemicals-capillary method
GB/T 2:781 2C08
Published by China Wuzhunshan Publishing House
No. 16-, Sanlihebei Street, Fuxingmenwai, Beijing
Handan Government Code: 100015
Net spe. net. cn
Tel: 6853394668517-48
Printed in Ningguo Changchengshanbanlansuhuangdao, distributed by Xinhua Bookstores all over the country
Format 880×12301/15
Printing sheet 0.75 Word count 13,000 words
First edition in July 2008
First printing in July 2008
Book number: 155066·1-32162 Price 14.C0 yuan If there is any printing error
Send it to the distribution center of our company for replacement
Copyright exclusive infringement will be investigated
Tel: (010) 68533533Repeat step 5 at least three times, take the average value, and get the sintering point and the full melting point. The temperature range from the sintering point to the full melting point is the melting range of the measured compound. Note: When the sample is heated, the following five changes will be observed (see 4): a) The wetting point is the stage where uniform small droplets are formed on the surface of the sample and the glass wall. When the sample begins to stick and a gap is formed between the inner wall of the glass and the sample. b) The sintering point
The stage where the sample begins to collapse and melt to the bottom of the capillary. e) The collapse point
The half-moon point
The full melting point
The stage where the collapsed sample is partially dissolved in the body and a complete half-moon is formed above the liquid. Stages of complete liquefaction of solid products
a) Wetting point b) Sintering point e) Collapse point d) Half-moon point e) Complete melting point Figure 4 Changes of samples when heated
7 Precautions for handling chemicals
When handling chemicals, first determine the product's terminology and safety characteristics. If the product's safety cannot be determined due to insufficient details of its physical properties, first investigate and study it, and then operate it after having a sufficient safety plan. When handling toxic, harmful, and radioactive chemicals that are legally restricted, you should follow the relevant laws and regulations and only operate after providing sufficient preparation and planning.
TTKAONTKAca-
GB/T 21781-2008
People's Republic of China
National Standard
Test method for melting point and melting range of chemicals-capillary method
GB/T 2:781 2C08
Published by China Wuzhunshan Publishing House
No. 16-, Sanlihebei Street, Fuxingmenwai, Beijing
Handan Government Code: 100015
Net spe. net. cn
Tel: 6853394668517-48
Printed in Ningguo Changchengshanbanlansuhuangdao, distributed by Xinhua Bookstores all over the country
Format 880×12301/15
Printing sheet 0.75 Word count 13,000 words
First edition in July 2008
First printing in July 2008
Book number: 155066·1-32162 Price 14.C0 yuan If there is any printing error
Send it to the distribution center of our company for replacement
Copyright exclusive infringement will be investigated
Tel: (010) 68533533Repeat step 5 at least three times, take the average value, and get the sintering point and the full melting point. The temperature range from the sintering point to the full melting point is the melting range of the measured compound. Note: When the sample is heated, the following five changes will be observed (see 4): a) The wetting point is the stage where uniform small droplets are formed on the surface of the sample and the glass wall. When the sample begins to stick and a gap is formed between the inner wall of the glass and the sample. b) The sintering point
The stage where the sample begins to collapse and melt to the bottom of the capillary. e) The collapse point
The half-moon point
The full melting point
The stage where the collapsed sample is partially dissolved in the body and a complete half-moon is formed above the liquid. Stages of complete liquefaction of solid products
a) Wetting point b) Sintering point e) Collapse point d) Half-moon point e) Complete melting point Figure 4 Changes of samples when heated
7 Precautions for handling chemicals
When handling chemicals, first determine the product's terminology and safety characteristics. If the product's safety cannot be determined due to insufficient details of its physical properties, first investigate and study it, and then operate it after having a sufficient safety plan. When handling toxic, harmful, and radioactive chemicals that are legally restricted, you should follow the relevant laws and regulations and only operate after providing sufficient preparation and planning.
TTKAONTKAca-
GB/T 21781-2008
People's Republic of China
National Standard
Test method for melting point and melting range of chemicals-capillary method
GB/T 2:781 2C08
Published by China Wuzhunshan Publishing House
No. 16-, Sanlihebei Street, Fuxingmenwai, Beijing
Handan Government Code: 100015
Net spe. net. cn
Tel: 6853394668517-48
Printed in Ningguo Changchengshanbanlansuhuangdao, distributed by Xinhua Bookstores all over the country
Format 880×12301/15
Printing sheet 0.75 Word count 13,000 words
First edition in July 2008
First printing in July 2008Www.bzxZ.net
Book number: 155066·1-32162 Price 14.C0 yuan If there is any printing error
Send it to the distribution center of our company for replacement
Copyright exclusive infringement will be investigated
Tel: (010) 68533533
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