JPS59196444A - Acid-concentration measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the concentration of a high concentration acid without dilution, by flowing a sample in a liquid feeding tube at a constant flow rate, adding a specified amount of an indicator to the sample mixing the sample and the indicator in a liquid feeding tube reaching a colorimeter, and discoloring the indicator. CONSTITUTION:A sample liquid is sent to a colorimetric flow cell 5a through a liquid feeding tube 3 by a constant flow rate pump 2, blank absorption at a colorimetric wavelength is measured, and thereafter the sample flows into a waste liquid receiving tank 7. Meanwhile, a specified amount of an indicator is injected to an indicator adding position 12 from an indicator tank 8 by a piston cylinder injector 9. The indicator and the sample are mixed while they flow in a mixing tube 13. The indicator is discolored in correspondence with the acid concentraion of the sample and put into the flow cell 5a. Thus, the absorption in the mixed state is measured. When the relationship between the acid concentration and the light absorption is obtained by a standard sample, the acid concentration can be measured.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to an acid concentration measuring device, and in particular to an acid concentration measuring device using a colorimetric method that is effective for measuring acid concentration in a sample in which a salt coexists in an acid solution. Regarding.

[Prior art and its problems]

Conventionally, acidity has been measured by measuring the pH value using a glass electrode,
Nine methods have been used: conductivity measurement, colorimetric measurement by adding a pH indicator after dilution, or titration. However, with a glass electrode, if the acid concentration exceeds 1N, accurate measurement cannot be performed due to the acid concentration difference, and it cannot be used for conductivity measurement when metal salts coexist. Furthermore, the titration method requires a long time for measurement, and when metal salts coexist, a large amount of complexing agent must be used to eliminate measurement errors due to hydrolysis of these metals. On the other hand, in colorimetric measurements, it is known that there are indicators that change color in acid solutions of several normal concentrations; however, if the acid in the sample has oxidizing properties such as nitric acid, the stability of the indicator is low. Therefore, sufficient measurement accuracy cannot be obtained.

[Purpose of the invention]

This invention improves the drawbacks of the conventional device mentioned above.
It is an object of the present invention to provide an acid concentration measuring device that can measure a highly concentrated acid of 1N or more without dilution.

[Summary of the invention]

The present invention uses a constant flow rate delivery mechanism for the measurement sample to flow the sample at a constant flow rate into the liquid delivery tube, and performs colorimetric detection by adding a fixed amount of an indicator, such as bromothymol blue, which changes color at an acid concentration higher than a specified concentration. This is an acid concentration measuring device that detects mixing and discoloration in the liquid delivery tube leading to the container.

〔Effect of the invention〕

By sending the measurement sample at a constant flow rate, it is possible to keep the time from the addition of the indicator until it flows into the colorimetric detector and detected, and to keep the mixing state of the sample and indicator constant. It is. Therefore, it is possible to measure the acid concentration with good reproducibility even when using a high concentration acid indicator that has low stability in an oxidizing acid such as nitric acid.

[Embodiments of the invention]

An embodiment of the acid concentration measuring device according to the present invention will be described below with reference to the drawings.

In FIG. 1, a liquid delivery tube 1 made of a material resistant to samples, such as Teflon, is connected to an external sample source (not shown), such as a sample tank, a sample flow path, etc., and a constant flow delivery mechanism, such as a constant flow plunger. The pump 2 sends the liquid to the liquid feeding tube 3 at a constant flow rate. If there is a pulsating flow in the constant flow delivery mechanism, a suitable result can be obtained by installing a pulsating flow removing mechanism, such as an air damper 4f, when expelling the liquid feeding tube 3. Under normal conditions, the sample is transferred to the liquid delivery tube 3.
The liquid flows through the colorimetric detection flow cell 5a of the colorimetric detector 5, and after the blank absorption of the sample at the colorimetric measurement wavelength is measured, it flows through the liquid feeding tube 6 into the waste liquid receiving tank 7. On the other hand, an indicator such as bromothymol blue is stored in an indicator tank 8, and is injected in a fixed amount into an indicator addition position 10 by operating an indicator regulating tf8 mechanism, such as a piston cylinder dispenser 9. In this case, a check valve 1 is installed in the indicator tube 11 near the indicator addition position 1o.
2 is more preferable because it can prevent the indicator from diffusing and outflowing outside the indicator addition position. When measuring the acid concentration, a fixed amount of indicator is injected using the piston cylinder dispenser 9 while the constant flow pump 2 is kept operating. The indicator and sample are mixed while flowing through the mixing tube 13, the indicator changes color depending on the acid concentration, flows into the colorimetric detection flow cell 5a, and absorption in the mixed state is measured.

Therefore, the acid concentration can be measured by determining the relationship between acid concentration and light absorption when using this device with a standard sample.

In addition, in the device according to the present invention, the amount of indicator added to the sample flow tK is extremely small, and when the mixing of the indicator into the sample is negligible, the liquid feeding tube 5 is connected to an external sample source (not shown). It is also possible to circulate.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an acid concentration measuring device according to the present invention. 1. Liquid feeding tube, 2. Constant flow plunger pump, 3.
Liquid feeding tube, 4 Air damper, 5 Colorimetric detector, 6.
・Liquid sending tube, 7 Waste liquid receiving tank, 8 Indicator holder, 9 ・Piston cylinder dispenser, 10 ・Indicator addition position, 1
1...Indicator addition tube, 12.Check valve, 13...
・Mixing tube

Claims (1)

[Claims] A mechanism that sends out measurement data at a constant flow rate, a mechanism that quantitatively injects an indicator that changes color depending on the acid concentration into the flow of the measurement sample, and a colorimetric detection mechanism that is installed downstream of the quantitative indicator injection mechanism. Acid concentration measuring device consisting of: