JPH0471175B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for testing the distillation of volatile substances.
More specifically, it relates to a method for measuring dry point in a distillation test for volatile substances. [Prior art] As a typical distillation test method for volatile substances, the Japanese Industrial Standards include "Fuel oil distillation test method" (JIS K-
2254-1980 (hereinafter referred to as JIS) is specified. This test method specifies a method in which a fixed volume of sample is distilled under predetermined conditions and the initial boiling point, distillation temperature, distillation amount, decomposition point, end point, and/or dry point, etc. are measured. It is said that there is no need to measure if the sample does not have a decomposition point. Each of the above terms is defined in JIS as follows. (1) Initial boiling point (°C): The reading on the thermometer when the first drop of distillate falls from the bottom of the condensing tube. (2) End point (℃): The highest temperature obtained during the distillation test.
This is usually seen after the sample at the bottom of the flask has completely vaporized. (3) Dry point (°C): The reading on a thermometer when the bottom of the flask is dry. At this time, the inner wall surface of the flask and the surface of the thermometer may be wet. <Remarks> Generally, the end point is more often used than the dry point, but the dry point is sometimes used in cases such as JIS K 2201 (industrial gasoline). For samples where the end point cannot be obtained with the specified accuracy,
Use dry point instead of end point. (4) Decomposition point (°C): The reading on the thermometer when the sample begins to undergo thermal decomposition. <Notes> Thermal decomposition can be recognized by the generation of white smoke and irregular temperature drops. (5) Distillation temperature (°C): Thermometer reading corresponding to the distillation volume. (6) Distillate volume (% by volume): Volume of distillate corresponding to thermometer reading. When measuring the initial boiling point according to the method specified in the above JIS, it is sufficient to read the reading on the thermometer when the first drop of distillate falls from the lower end of the condensing tube, or When measuring the temperature of the distillate amount (volume %), it is sufficient to read the indicated value of the thermometer when a predetermined distillate amount is reached. The end point can be determined by reading the maximum temperature indicated by a thermometer after the distillation flask is emptied. However, the dry point is defined as "the reading on the thermometer when the bottom of the distillation flask is dry," so when measuring it, carefully observe the conditions inside the distillation flask and decide when to take the measurement. That is, it is necessary to determine the timing of measurement. However, according to the JIS regulations, in order to maintain the distillation rate of the sample at a predetermined rate and to prevent any danger from occurring under normal usage conditions, distillation must be carried out using a metal windshield of approximately 100 to 100 mm. It is supposed to cover the test equipment. A viewing window (70 mm or more in diameter) is required to be attached to the windshield in order to observe the condition of the distillation flask. It is difficult to observe the distillation flask through this viewing window and determine the moment when the bottom part of the flask is dry, and the dry point is often measured at a point far past the original point of view. The timing of dry point measurement may change. Therefore, variations in measured values tend to occur, which poses a major problem in terms of measurement accuracy. In addition, visual observation requires the person performing the measurement exclusively, and is not a preferable method in terms of labor saving in measurement. [Problems to be Solved by the Invention] An object of the present invention is to provide a distillation test method that solves the above problems and enables dry point measurement with high accuracy. [Means for Solving the Problem] As a result of intensive study, the present inventors found that in a distillation test, the temperature at the bottom of the distillation flask rapidly increases when the dry point is reached, using a special thermometer. The inventors have discovered that the above object can be achieved by detecting the temperature and measuring the distillation temperature at this time, leading to the present invention. That is, in the distillation test of volatile substances, the present invention (1) installs the thermometer (A) so that the detection part of the thermometer contacts the bottom of the distillation flask;
(B) is installed so that the detection part of the thermometer is located slightly below the branch point of the branch pipe of the distillation flask, and (3) after the distillation of the test substance to be distilled is completed, This distillation test method is characterized by using a thermometer (A) to detect the point in time when the temperature of the sample (A) suddenly increases, and the reading on the thermometer (B) at this time being taken as the dry point. A feature of the present invention is that two thermometers (A) and (B) are used, and (A) is placed in contact with the bottom of the distillation flask to detect the timing of dry point measurement. Its purpose is to use it as a thermometer. In the present invention, thermocouple thermometers are preferably used as the thermometers (A) and (B). In the present invention, "the distillation of the test substance to be distilled is completed" means that the test substance to be distilled has been distilled out and no test substance to be distilled remains in the distillation flask. The signs of this condition depend on the type of test substance to be distilled and the amount of sample, but in general, the distillation amount is between 95 and 98
This is determined by whether the amount of distillation becomes approximately % by volume or more, or by the fact that the amount of distillation per unit time, for example, per minute, becomes extremely small. If the distillation amount per unit time is extremely well controlled, this can also be determined by measuring the elapsed time from the start of the distillation test. Therefore, at least when the above-mentioned sign that "the distillation of the test substance to be distilled is finished" appears, the thermometer (A) must be started to detect the timing of dry point measurement. The specifications of the distillation test equipment such as the distillation flask, condenser, wind shield, flask support stand and plate, receiver, etc. used in the present invention, the conditions of the distillation test, and the test procedure are as follows:
Those specified in JIS are preferably used. The thermometer used in the present invention is preferably a thermocouple thermometer rather than a glass rod mercury thermometer or a platinum resistance thermometer. Thermocouple thermometers are suitable for measuring the temperature of minute parts because the detection part is a minute joint between two types of metal, and it is suitable for measuring the temperature of a small amount of residual liquid in a distillation flask. This is preferable in that it is possible to accurately detect the point in time when the inside of the distillation flask becomes empty. It is also preferable in that temperature changes can be measured as changes in current. There are no particular restrictions on the type of thermocouple thermometer; the commonly used chromel/alumel types,
Iron/constantan type etc. are preferably used. Furthermore, when an electric heater is used to heat the distillation flask, the temperature change at the bottom of the flask can be measured by measuring minute changes in the electrical resistance of the electric heater itself. On the other hand, glass rod-shaped mercury thermometers are not suitable for use as an instrumentation mechanism that connects two thermometers online, and electric conduction resistance thermometers have a detection part of about 100 mm in length, so It is not suitable for measuring the temperature of minute parts. Hereinafter, embodiments of the present invention will be described in detail using the drawings. FIG. 1 shows a cross-sectional view of a part (a part where a distillation flask and a thermometer are installed) of an example of a distillation test apparatus used in the present invention. The distillation flask 1 is a flask with two branch pipes. Measure the temperature at the bottom 6 of the flask with a thermometer 5 (corresponding to the above thermometer (B)) to measure the temperature (distillation temperature) from the mouth 3 of the flask to a point slightly below the branch point 4. Insert thermometer 7 (corresponding to thermometer (A) above). The thermometer 5 is installed so that its detection part is located at a location specified by JIS. The thermometer 7 is installed so that its detection part is in contact with the bottom of the flask. A predetermined amount (usually 100 ml) of the test substance 8 to be distilled is placed in the distillation flask 1, and the distillation flask 1 is heated from the bottom using an electric heater or the like. When the temperature of the test substance 8 to be distilled begins to rise due to heating, it gradually vaporizes, and the vaporization becomes intense at the boiling point, and the generated gaseous test substance 8 to be distilled reaches the condensation pipe from the branch point 4 through the branch pipe 2. , is cooled and becomes a condensate. The condensate is received in a receiver. The reading on the thermometer 5 when the first drop of distillate falls from the lower end of the condensing tube is defined as the initial boiling point. Adjust the heating rate so that the time from the start of heating until reaching the initial boiling point falls within the range specified by JIS. A distillation temperature corresponding to a specified distillation amount (volume %) and/or a distillation amount corresponding to the specified distillation temperature are defined from the initial boiling point to the end of distillation. When the condensate in the receiver reaches a predetermined amount, the reading on the thermometer 5 is taken as the distillation temperature. The method for measuring the distillation temperature corresponding to the initial boiling point and specified distillation amount is to
For example, an optical sensor or the like is used to automatically detect that a drop has fallen or that the condensate in the receiver has reached a specified amount, and the signal is used to set the thermometer 5.
Preferably, the instrumentation mechanism automatically records the support value of . To measure the dry point, as described above, the thermometer 5 and the thermometer 7 are connected instrumentally, and when the thermometer 7 detects a sudden temperature change, the signal is transmitted to the thermometer 5 using, for example, an electric signal. The value indicated on the thermometer 5 at that time is taken as the dry point. A preferred method is to use thermocouple type thermometers as thermometer 5 and thermometer 7, and to use an instrumentation mechanism that automatically records the readings of both thermometers. That is, the temperature of the lowest part 6 in the distillation flask is measured using the thermometer 7 from the time when the distillation of the test substance 8 to be distilled is almost completed. The moment the distillation test substance 8 is completely vaporized and the bottom 6 of the distillation flask becomes dry, the reading on the thermometer 7 will begin to rise rapidly.The reading on the thermometer 5 at this time is detected and determined as the dry point. do. Although the dry point measurement timing of the present invention is performed from the time when the distillation of the test substance 8 to be distilled is almost completed, it may be performed from the time when the distillation test is started. Furthermore, in the method of the present invention, the decomposition point of any liquid substance that generates heat upon decomposition can be measured in the same manner. In addition, when testing substances to be distilled that contain substances with extremely different distillation temperatures, the method for measuring the dry point of the present invention is applied after each distillate has been distilled. Therefore, the distillation temperature and distillation amount of each distillate can be measured. In the present invention, it is possible to apply the method and apparatus specified in JIS except for measuring the rapid temperature change at the bottom of the flask. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 Automatic distillation tester (manufactured by Meihosha Seisakusho, model: 25B)
-17AD3P), two thermocouple type thermometers were used to be installed inside the flask. One of the thermometers (thermometer A) was installed so that its detection part was in contact with the bottom of the flask, so that changes in temperature at the bottom of the flask could be measured. The detection part of the other thermometer (thermometer B) is JIS
It was installed at the position specified by , that is, slightly below the branch point of the branch pipe of the flask, so that the distillation temperature could be measured. As a distillation test sample, a distillation test was conducted using standard sample A listed in Appendix Table 1 of JIS. In addition, 21 minutes after reaching the initial boiling point, we started measuring the temperature change at the bottom of the flask.
A rapid temperature rise at the bottom of the flask was detected with thermometer A, and the reading on thermometer B at that time was taken as the dry point.
The dry point obtained was 203.1°C. As a result of repeating the same test five times, the dry point was
The temperature was 202.8 to 203.2°C, and the repeatability was extremely good. (Average value 203.0℃, standard deviation
0.091℃). Comparative Example 1 A distillation test was conducted in the same manner as in Example 1, except that the dry point measurement timing was detected visually inside the flask. The dry point obtained was 203.2°C. As a result of repeating the same measurement five times, the dry point was
The range of measured values was 202.9 to 203.5°C.
(Average value 203.2℃, standard deviation 0.11℃). JIS K-2254 Annex Table 1 is shown below.

【table】

〔Effect of the invention〕

According to the method of the present invention, dry point detection in a distillation test is more accurate than by visual inspection, and a dry point with high repeatability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the flask portion of the apparatus of the invention. In the figure, 1... distillation flask, 2... branch pipe, 3... flask neck, 4... branch point, 5, 7...
...Thermometer, 6... Bottom of distillation flask, 8...
Distillable test substance.

Claims (1)

[Claims] 1. In a distillation test for volatile substances, (1) a thermometer (A)
(2) Install the thermometer (B) so that the detection part of the thermometer is in contact with the bottom of the distillation flask, and (2) install the thermometer (B) so that the detection part of the thermometer is slightly below the branch point of the branch pipe of the distillation flask. (3) Use the thermometer (A) to detect the point in time when the distillation of the test substance to be distilled has finished and the temperature at the bottom of the distillation flask suddenly rises. A distillation test method characterized by using the reading on the thermometer (B) as the dry point. 2. The distillation test method according to claim 1, wherein the thermometer (A) and the thermometer (B) are thermoelectric thermometers.