JP2007108100A - Quantitative method for tungsten bronze - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of determining quantitatively alkali metal in a tungsten bronze capable of preventing the alkali metal from being volatilized partially in the form of an oxide. <P>SOLUTION: An alkaline solution is added to a sample of the tungsten bronze containing the alkali metal, the sample is heatedly decomposed by a microwave heating decomposition method, and the alkali metal is thereafter determined quantitatively. A temperature is preferably controlled at 200°C or less when the sample is heated by the microwave heating decomposition method. The alkaline solution is preferably an alkali hydroxide solution or an alkali carbonate solution. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for quantifying alkali metals in tungsten bronze.

  In recent years, tungsten bronze has been increasingly demanded as a heat ray shielding material used for buildings and car windows. Important characteristics of the heat ray shielding material include ultraviolet absorption and visible light transmission. The amount of alkali metal contained in tungsten bronze greatly affects the above characteristics, and it is extremely important to accurately grasp these contents.

However, since tungsten bronze has characteristics such as high corrosion resistance, it is very difficult to make a sample into a solution by a normal acid decomposition method. As a method for dissolution, an alkali melting method using sodium peroxide or the like (Non-Patent Document 1) has been proposed.
Analytical Chemistry (Bunseki Kagaku), 30, 599 (1981) "Element loss associated with dry ashing of plant samples"

  In the method described in the above-mentioned non-patent document, it is necessary to heat to a high temperature of, for example, 900 ° C. at the time of melting, so that the alkali metal may partially volatilize in the form of an oxide and the target component may be lost. There is sex.

  Therefore, an object of the present invention is to provide a method for quantifying alkali metal in tungsten bronze that can prevent alkali metal from partially evaporating in the form of an oxide.

  The method for quantifying alkali metal in tungsten bronze according to the present invention is characterized in that a sample of tungsten bronze, which is a sample, is added with an alkaline solution to form a solution by microwave thermal decomposition, and then the alkali metal in the sample is quantified.

  According to the present invention, the alkali metal in the tungsten bronze can be made into a solution without loss, and the alkali metal in the tungsten bronze can be quantified.

  As a method for solving these problems, the present invention makes it possible to quantify without losing the target component by adding an alkaline solution to the tungsten bronze as a sample and making it a solution by the microwave thermal decomposition method. .

  The method for quantifying alkali metal in tungsten bronze according to the present invention will be described in detail as follows.

  The sample is weighed into a polytetrafluoroethylene resin container for microwave thermal decomposition, and 10 ml of 10 wt% sodium hydroxide solution is added. Next, the polytetrafluoroethylene resin container is set in a microwave thermal decomposition apparatus, sealed, and thermally decomposed. At this time, although the decomposition time can be shortened by heating at a higher temperature, about 200 ° C. is preferable so that the polytetrafluoroethylene container is not deformed.

  After the sample is decomposed and made into a solution by the above method, a sulfuric acid (1 + 1) solution containing 5% hydrogen peroxide is added to make the solution acidic, and water is added to adjust the amount of the solution to a constant volume to obtain a sample solution. After diluting appropriately, the farming degree in the solution is measured by flame atomic absorption spectrometry. The alkali metal in tungsten bronze can be quantified by the above method.

According to the present invention, Na, K, Rb, Cs and W in various tungsten bronze samples were quantified. Hereinafter, the present invention will be described based on examples.
Example 1
A tungsten bronze sample is weighed into a polytetrafluoroethylene resin container for microwave thermal decomposition, and 10 ml of 10 wt% sodium hydroxide solution is added. Next, a polytetrafluoroethylene resin container is set in a microwave thermal decomposition apparatus, sealed, and thermally decomposed. At that time, thermal decomposition is performed for about 1 hour with the upper limit of output being 600 W and the upper limit of temperature being (IR monitor) 200 ° C. so that the temperature does not exceed 200 ° C. After standing to cool, 30 ml of sulfuric acid (1 + 1) solution containing 5% hydrogen peroxide is added to a polytetrafluoroethylene resin container for microwave thermal decomposition. After cooling, the resulting solution was transferred to a 250 ml flask, water was added to adjust the volume to 250 ml, and this was used as a sample solution. The measurement conditions were as shown in Table 1 below, and measurement was performed using a flame atomic absorption spectrometer (AAS) and an ICP-emission spectroscopic analyzer (ICP-AES).

  However, the unit of the fuel flow rate is ml / min.

  The quantitative results are shown in Table 2 below. For comparison, the same sample is dissolved by the sodium peroxide melting method, and the results obtained are also shown. From the results, the same quantitative value was obtained for both methods for W, whereas for alkali metals, the quantitative value obtained by the alkali melting method was the quantitative value obtained by the thermal decomposition method for micro. As a result, a low value was obtained. From this fact, it is considered that the alkali metal as the target component is lost in the alkali melting method.

(Example 2)
In the decomposition, quantification was performed in the same manner as in Example 1 except that a 10 wt% potassium hydroxide solution was used as the alkaline solution to be used. The results are shown in Table 3 below. A result in good agreement with Example 1 was obtained.

(Example 3)
At the time of decomposition, quantification was performed in the same manner as in Example 2 except that a 10 wt% sodium carbonate solution was used as the alkaline solution to be used. The results are shown in Table 4 below. Results in good agreement with Example 1 and Example 2 were obtained.

Example 4
At the time of decomposition, quantification was performed in the same manner as in Example 2 except that a 10 wt% potassium carbonate solution was used as the alkaline solution to be used. The results are shown in Table 5 below. The results are in good agreement with the above examples.

Claims (3)

  A method for quantifying alkali metal in tungsten bronze, comprising adding an alkaline solution to a tungsten bronze sample containing an alkali metal, thermally decomposing the sample by a microwave thermal decomposition method, and then quantifying the alkali metal.   The method for quantifying an alkali metal in tungsten bronze according to claim 1, wherein the temperature at which the sample is heated by the microwave pyrolysis method is controlled to 200 ° C or lower.   2. The method for quantifying an alkali metal in tungsten bronze according to claim 1, wherein the alkali solution is an alkali hydroxide solution or an alkali carbonate solution.