JPH04299242A - Specific heat measuring apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal analysis apparatus, and more particularly to a specific heat measuring apparatus for measuring the specific heat of a substance to be measured.

0002

2. Description of the Related Art A differential scanning calorimeter (DSC) is used to measure the specific heat of a substance. In a differential scanning calorimeter, two sample dishes are arranged in a heating furnace, and a temperature detection means that can detect the temperature difference between the sample dishes is provided, and the heating furnace is heated so that the temperature of the heating furnace rises at a constant rate. When measuring the specific heat of a substance to be measured, measurements are performed twice under the same conditions using a standard substance whose specific heat is known and a substance to be measured whose specific heat is to be determined as samples.

0003

[Problems to be Solved by the Invention] Since the conventional measuring apparatus measures the standard substance and the substance to be measured separately, measurement errors are inevitable even if the same conditions are set. When the substance to be measured contains volatile components such as water, the volatile components evaporate during measurement and the weight of the substance to be measured changes. Even if volatile components are removed before measurement and the weight of the substance to be measured is measured, the substance to be measured may absorb water and change in weight during the measurement until the specific heat is measured. In such a case, conventional differential scanning calorimeters cannot detect weight changes during measurement, so measurement errors due to weight changes cannot be avoided.

[0004] The present invention makes it possible to simultaneously measure a substance to be measured and a standard substance in one measurement, thereby simplifying the operation, increasing measurement accuracy, and also measuring changes in weight of the substance to be measured during measurement. It is an object of the present invention to provide a specific heat measuring device that can further improve measurement accuracy in this manner.

[0005]

[Means for Solving the Problems] In the present invention, a pair of detection sections are arranged in a heating furnace that heats at a constant speed, and each detection section has two detection sections.
At least one of the detection parts is connected to a balance, and the substance to be measured is placed on the detection part connected to the balance. Then, the temperature is measured by the temperature detection means of the detection part and the weight change is measured by the balance.The standard substance is placed on the other detection part and the temperature is measured by the temperature detection means of the detection part. Specific heat is measured after correction for weight changes.

[0006]

[Function] When a substance to be measured is placed as a sample on one detection part, and a standard substance is placed as a sample in the other detection part, and both samples are simultaneously heated in a heating furnace and measured, the difference between the substance to be measured and the standard substance is measured. A signal proportional to the specific heat can be obtained simultaneously in one measurement. In addition, since the detection part where the substance to be measured is connected to the balance, the weight change of the substance to be measured during measurement is subtracted from the original weight of the substance to be measured to obtain the weight of the substance to be measured when calculating the specific heat. The true specific heat calculation is done by

[0007]

Embodiment FIG. 1 shows an embodiment. 2 is a cylindrical heating furnace, and the inside thereof is heated at a constant speed by a heating furnace control section (not shown). A pair of detection units 4 and 6 are provided in the heating furnace 2.
is accommodated. One detection unit 4 has two sample dishes 4a.
, 4b, and the other detection section 6 also has two sample dishes 6a, 6.
It is equipped with b. Each detection section 4, 6 is attached to the tip of a beam 8, 10 of a respective horizontal differential type balance.

[0008] In each of the detection units 4 and 6, each sample dish is provided with a thermocouple for measuring temperature.
The thermocouples of each sample plate are connected in series so that their polarities are reversed, so that the temperature difference between the sample plates can be detected in each of the detection units 4 and 6. That is, as shown in FIG.
2a, 12b), the respective temperatures of the reference side sample plate 4a and sample side sample plate 4b and the temperature difference ΔT1 are detected,
In the other detection unit 6, the thermocouple 14 (14a, 14b)
Accordingly, the respective temperatures of the reference side sample plate 6a and the sample side sample plate 6b and the temperature difference ΔT2 are detected. Although not shown in the figure, a data processing section is provided, and the thermocouple 1
The detection signals No. 2 and 14 and the weight detection signal of the balance are taken into a data processing section, and the specific heat of the substance to be measured is calculated.

Next, a method of measuring specific heat using the apparatus will be explained in this embodiment. As shown in FIG. 3, an empty cell 16 is placed on the reference side 4a of one detection section 4, a reference substance 18 with a known specific heat is placed on the sample side 4b, and an empty cell 16 is placed on the reference side 6a of the other detection section 6. 20, and the substance to be measured 22 whose specific heat is to be determined is placed on the sample side 6b. Since the standard substance 18 and the substance to be measured 22 are placed in cells and placed on the sample plate, empty cells 16 and 20 are also placed on the sample plate on the reference side.

[0010] During measurement, the sample is heated according to a heating program in which the temperature increases at a constant rate, as shown in FIG. In both detection units 4 and 6, their thermocouples 12 and 1
4, the temperature difference signals ΔT1 and ΔT as shown in FIG.
2 is obtained. In these temperature difference signals, as is well known, the base line shift amounts h1 and h2 of ΔT1 and ΔT2 at that temperature are proportional to the specific heat at that temperature. The specific heat C2 of is C2=
It can be determined as C1×(h2/h1)×(W1/W2). Here, C1 is the specific heat of the standard substance at that temperature, and W1 and W2 are the weights of the standard substance and the measured substance, respectively. This formula calculates the specific heat assuming that the sample weight does not change during the measurement.

By the way, when the substance to be measured is a sample containing volatile components, the latent heat of vaporization causes Δ
T drifts and weight decreases due to volatilization. Therefore, the specific heat is calculated from point A after volatilization ends to point B, and the sample weight when calculating the specific heat is the initial sample weight W2 minus the reduction δ obtained in this measurement. use. As a result, the formula for calculating specific heat with correction due to weight change is as follows: C2=C1×(h2/h1)×{W1/(W2-δ)}
In the embodiment, both the detection section on the side of the substance to be measured and the detection section on the side of the standard substance are attached to the tip of the beam of the balance, but only the side of the substance to be measured may be attached to the beam of the balance. In the embodiment, the detection section is attached to the tip of the beam of a horizontal balance, but the present invention can also be applied to an upper pan type or hanging type balance.

0012

[Effects of the Invention] In the present invention, a pair of detection parts are provided in the heating furnace so that the measured substance and the standard substance can be measured simultaneously, so the specific heat can be determined in one measurement, and the operation is easy. The measurement accuracy improves as well. At least the detection part on the side of the substance to be measured is connected to the balance, so weight changes during measurement can be detected at the same time, and the weight change can be corrected when calculating the specific heat, which improves measurement accuracy. further improves.

[Brief explanation of drawings]

FIG. 1 is a front sectional view showing one embodiment.

FIG. 2 is a diagram showing connections of thermocouples in each detection section.

FIG. 3 is a diagram showing how to place a sample during specific heat measurement.

FIG. 4 is a diagram showing a temperature program during specific heat measurement.

FIG. 5 is a diagram showing a temperature difference signal during specific heat measurement.

FIG. 6 is a diagram showing a measurement signal when the weight of the substance to be measured changes during measurement.

[Explanation of symbols]

2 Heating furnace 4, 6
Detection parts 4a, 4b, 6a, 6b Sample dishes 8, 10
Balance beam 12, 12a, 12b, 1
4, 14a, 14b thermocouple

Claims (1)

[Claims] Claim 1: A pair of detection units are disposed in a heating furnace that heats at a constant rate, each detection unit comprising two sample dishes and temperature detection means capable of detecting the temperature of the sample dishes and the temperature difference thereof, At least one of the detection parts is connected to a balance,
The substance to be measured is placed on a detection part connected to the balance, the temperature is measured by the temperature detection means of the detection part, and the weight change is measured by the balance, and the standard substance is placed on the other detection part and the temperature is measured by the temperature detection means of the detection part. A specific heat measuring device in which temperature is measured by a temperature detecting means, and specific heat is measured by making corrections based on changes in weight of a substance to be measured.