JPH0241698B2 - - Google Patents

Description

[Detailed Description of the Invention] To accurately measure the melting point, the temperature sensing part of the thermometer must be brought into direct contact with the sample, and the temperature must be kept constant for a certain period of time during the melting and solidification processes. need to be confirmed. However, in the production of drugs, etc., it is considered most desirable that a small amount of sample is sufficient, even if the accuracy is somewhat poor.

In the recent 9th revised Japanese Pharmaceutical Law, the melting point measurement method is stipulated as follows. Inner diameter 0.8~1.2mm,
A powder sample is placed in a hard glass capillary tube with a wall thickness of 0.2-0.3 mm and a length of 120 mm, closed at one end. Place the capillary tube containing the sample and a mercury thermometer into the silicone oil bath in a transparent container, place the part of the capillary tube containing the sample near the bulb of the mercury thermometer, and heat it from the outside. Confirm with the naked eye that the sample in the tube is melting, and use the temperature indicated by the mercury thermometer at that time as the melting point of the sample. In this indirect method of melting point measurement, the required minimum amount of sample is determined on the condition that melting can be confirmed with the naked eye, so the temperature of the sample is continuously measured and the temperature of the sample is continuously measured to confirm the melting and solidification processes. Compared to the direct method, which confirms that the temperature is kept constant over time, a much smaller amount of sample is required. However, the measurement accuracy is not good.

The present invention relates to a melting point measuring device that has been improved so that it can measure with higher accuracy than previous devices using the above-mentioned indirect method of heating a sample through a bath liquid.

With a glass tube containing a sample and a mercury thermometer,
Because their heat conduction methods and heat capacities are significantly different,
The temperature rise due to indirect heating is significantly different.
This is considered to be the main reason for the difference in temperature between the mercury thermometer and the sample. The improvement mainly lies in this point.

In the apparatus of the present invention, the main objective is to make the shape, size, etc. of the temperature sensing part of the thermometer as similar as possible to the glass capillary tube containing the sample.

The figure shows an embodiment of the heating section of the device according to the invention. 1
3 is a first glass capillary tube containing sample 2, and 3 is a second glass capillary tube, preferably the same as 1, in which a temperature measuring junction 4 of a thin wire thermocouple is inserted. 5 is a heating bath liquid (silicon oil), 6 is a transparent container, and 7 is a gas burner. It is even better if a powder similar to the sample but with a high melting point is placed in the second glass capillary 3.

Care should be taken to place 1 and 3 close to each other and to use the same heating conditions as possible.

Heating is not limited to being performed using the gas burner 7, but may be performed by any appropriate method. Furthermore, the bath liquid is not limited to silicone oil. The temperature-sensing part inserted into the second glass thin tube 3 is not limited to the temperature-measuring junction 4 of a thermocouple, but may be a small temperature-sensing part such as a thermistor, but it is better to use the temperature-measuring junction 4 of a thin wire thermocouple. has the following advantages over thermistors.

) The amount of heat in the temperature sensing part is small.

) The temperature range that can be measured is wide.

) Can be used as an articulated thermometer.

In particular, it can be used as a connected thermometer by connecting it with a resistance thermometer.
If you set the connection temperature to a temperature close to the measured temperature,
Accurate measurements can be made.

In the figure, 8 is a connection part with a resistance thermometer 9, and 10 is a circuit and an instrument part of the connection thermometer.

[Brief explanation of the drawing]

The drawing is a sectional view showing an embodiment of the bath liquid heating type melting point measuring device according to the present invention. 1...First glass tube, 2...Sample, 3...
Second glass capillary, 4...Temperature measuring junction of thermocouple, 5
...Bath liquid, 6...Transparent container, 7...Gas burner, 8...Connection part of the connecting thermometer, 9...Resistance thermometer, 10...Circuit and instrument part of the connecting thermometer.

Claims (1)

[Scope of Claims] 1. A container 6 that accommodates a heating bath liquid 5 and whose interior can be seen through; A container 6 that accommodates a sample 2 whose melting point is to be measured;
A first glass thin tube 1 is inserted into the heating bath liquid 5 in the heating bath liquid 5, and the temperature sensitive part 4 of the temperature sensor is accommodated, and the first glass thin tube 1 is inserted into the heating bath liquid 5 in the vicinity of the first glass thin tube 1. A bath liquid heating type melting point measuring device comprising: a second glass capillary 3 having the same shape and size as the first glass capillary 1; 2. The bath liquid heating type melting point measuring device according to claim 1, wherein the temperature sensing part 4 of the temperature sensor is a temperature measuring junction of a thermocouple. 3. The bath liquid heating type melting point measuring device according to claim 2, wherein the thermocouple is connected to a resistance thermometer 9. 4. The bath liquid heating type melting point measuring device according to claim 1, wherein the temperature sensing part 4 of the temperature sensor is a temperature sensing part of a thermistor. 5. The bath liquid heating type melting point measuring device according to any one of claims 1 to 3, wherein the second glass capillary tube 3 contains a powder having a higher melting point than the sample 2.