SU1198393A1 - Method of calibrating differential scanning calorimeter - Google Patents

Abstract

A METHOD FOR CALIBRATING A DIFFERENTIAL SCANING CALORIMETER, which includes filling out chambers with a standard liquid, creating a calibration effect in one of the chambers, changing the heat capacity of its contents, registering the output signal, corresponding to the calibration effect, and determining the scale factor of the calibrated calorimeter, I’ve done it, I’ve done it, I’ve done it, I’ve done it, I’ve done a lot of trouble. the calibration effect is created by partially replacing the reference fluid in one of the chambers with a solid reference fluid. inert to the reference fluid, and the scaling factor is determined from the calculated value of the differential heat capacity V, calculated by the formula:, fi (. -C,), -dC m (L where m is the mass of the solid standard; fi fl -density reference liquid and solid standard, respectively; C. i S -specific heat capacities CO 00 00 CO 00 reference liquid and solid standard.

Description

The invention relates to calorimetric measurements and can be used in the certification, verification or calibration of differential scanning calorimeters designed to measure the differential volumetric heat capacity of liquids, i.e. calorimeters in which the chambers have a constant capacity, and the dosing of the amount of the investigated liquid is carried out due to the 100% filling of the chambers through the supply tubes.

The purpose of the invention is to increase the accuracy of calibration by differential heat capacity of differential scanning calorimeters designed to measure differential volumetric heat capacity of liquids.

The proposed method for calibrating calorimeters is as follows.

Both calorimetric chambers are filled with a reference liquid, for example, distilled water, for which the density and specific heat are known in a wide temperature range. The calorimeter chambers filled with the reference liquid are heated or cooled in the temperature range of interest and with the heating or cooling rate of interest and the baseline of the calorimeter is recorded, i.e. the line with respect to which the output signal of the calibrated calorimeter is subsequently counted.

I

In order to create a calibration effect, a solid standard is placed in one of the calorimetric chambers filled with the reference liquid, for which the specific heat and density are known in this temperature range. Given that the calorimetric chambers have a constant capacity of the measuring part, which is filled with the reference liquid, a solid standard will displace part of the reference liquid from the measuring volume of the calorimetric chamber, and since the heat capacity of the standard differs from the heat capacity of the displaced part of the liquid standard, the heat capacity of this calorimetric chamber with the contents in it substance will change by a value whose value can be calculated by the above formula. Then, a change curve of this difference calibration heat capacity is recorded in the same temperature range and at the same scanning speed as the baseline. In this case, the output signal of the calibrated calorimeter corresponding to the calibration action is the distance from the baseline for the recorded curve. The scale factor of the calibrated calorimeter is calculated as the ratio of the value of the calibration effect to the output signal corresponding to the calibration effect at a given temperature. The analysis of the calibration error arising when using the proposed method is carried out. The differential formula for estimating the error of the proposed method has the form

AC

A 0 * 2 +

Each component of the error sG (hp) is determined separately. After differentiation (d ^C G ^C f ^t 2 ^{+ t} 2 ^ 2 ^{+ No.} 2 ^LS 2 ⁺

Pi

To estimate the error value of the proposed method at a temperature of ₃₅ ° C and 25 ° C, make the substitution of digital values using the certificate for a stationary sample of thermodynamic properties “leucosapphire No. 149-76 40 according to the Federal Register of the USSR.

m ₂ = 1-10 ² g; p ₂ = 3.96 - ₃ ; C ₂

- about. '”ξ-τ; s, 45 = 4.1807 dsh ₂ = 5-10 ^ g;

L0- » _lSg . .., o-> y-.

'-'O-''0 - 1.10- ⁴ -®, where gm ₂ - maximum error in weighing scales VLR 20 (remaining error determined by the accuracy of table data 55).

After the calculation, we get <ЛдС) =

Claims (1)

METHOD FOR CALIBRATING A DIFFERENTIAL SCANNING CALORIMETER, including filling the chambers with a reference liquid, creating a calibration action in one of the chambers by changing the heat capacity of its contents, recording an output signal corresponding to the calibration action and determining the scale factor of the calibrated calorimeter, which is different in order to increase the accuracy gauge "effect is created by partial replacement of the reference fluid in one of the chambers with a solid reference substance Inert to the reference liquid, and a scale factor is determined from the calculated value of the specific heat dC of the difference, calculated by the formula: 4C - w 2 · (p ~ C _l -), where mj is the mass of the solid standard; ί Pr ~ the density of the reference liquid and solid reference, respectively; FROM, ; C ₂ - specific heat of the reference fluid and · solid reference. SU ", 1198393