JP2006284206A - Reagent for judging iron component, presence judging method of iron component and concentration measuring method of iron component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply judge the presence of an iron component in water to be tested. <P>SOLUTION: This reagent for judging the iron component contains a first agent for reducing trivalent iron ions to divalent iron ions and the second agent mixed with the first agent to react with divalent iron ions to form a color. When the reagent is added to water to be tested, the trivalent iron ions in the water to be tested are reduced to divalent iron ions by the first agent. The formed divalent iron ions and the divalent iron ions present in the water to be tested from beginning are reacted with the second agent to form a color. The presence of the iron component can be judged on the basis of the formed color. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reagent for determining iron content, a method for determining the presence or absence of iron, and a method for measuring the concentration of iron, in particular, a reagent for determining the presence or absence of iron in test water, a method for determining the presence or absence of iron using this reagent, and iron. The present invention relates to a method for measuring concentration.

  Raw water such as tap water used as boiler feedwater usually removes deoxygenation and hardness components that remove dissolved oxygen, ie, calcium and magnesium, in order to prevent corrosion and scale formation in the boiler. Water softening treatment is applied. Here, the deoxygenation treatment is usually performed by treating raw water with a separation membrane. In addition, the water softening treatment is usually performed by treating raw water with an ion exchange resin.

  By the way, raw water such as tap water may contain iron. This iron may clog the separation membrane used in the deoxygenation treatment and impair the deoxygenation efficiency of the raw water, and may adsorb on the ion exchange resin used in the water softening treatment, preventing the softening of the raw water. There is sex. Therefore, the raw water used as boiler feedwater is usually removed by iron removal equipment such as tower-type filtration equipment or sand filtration equipment using particulate manganese chamotte or manganese zeolite as a filter medium before deoxidation treatment and water softening treatment. Iron has been removed. Therefore, it is preferable to confirm that iron is removed from raw water before it is deoxygenated and softened.

  As a method for determining the presence or absence of iron in water, Non-Patent Document 1 presents an absorptiometric method using 1,10-phenanthroline. In this method, first, iron in test water is dissolved with an acid, and trivalent iron ions are reduced to divalent iron ions with hydroxylamine hydrochloride (first step). Then, 1,10-phenanthroline that reacts with divalent iron ions to produce an orange-red complex compound is added to the water to be tested (second step). Here, when the water to be tested changes its color to orange-red by the complex compound, it can be determined that iron is present in the water to be tested, and when the amount of color change in the water to be tested is measured by absorptiometry, The iron concentration of test water can also be determined. On the other hand, when the water under test does not change color, it can be determined that the water under test does not contain iron.

  However, since the above-described determination method requires two steps, a first step using hydroxylamine hydrochloride and a second step using 1,10-phenanthroline, the determination step is complicated.

  An object of the present invention is to enable easy determination of the presence or absence of iron in the water under test.

Published by Japan Water Works Association, “Water Supply Test Method 2001”, pages 340-342

  The iron content determination reagent of the present invention is for determining the presence or absence of iron content in the water under test, and is mixed with a first agent for reducing trivalent iron ions to divalent iron ions, and the first agent. And a second agent that develops color by reacting with divalent iron ions.

When the iron content determination reagent of the present invention is added to the test water containing only the iron content of the trivalent iron ion (Fe ³⁺ ) or the iron content of both the trivalent iron ion and the divalent iron ion (Fe ²⁺ ), the trivalent iron Ions are reduced to divalent iron ions by the first agent. The divalent iron ions generated in this way and the divalent iron ions originally contained in the water under test react with the second agent to develop color. Thereby, it can be determined that the water under test to which the reagent for determining iron content is added contains iron. In addition, when the iron content determination reagent of the present invention is added to the water to be tested containing only the iron content of the divalent iron ion, the divalent iron ion reacts with the second agent and develops color. Thereby, it can be determined that the water under test to which the reagent for determining iron content is added contains iron. Furthermore, when the reagent for determining iron content of the present invention is added to water to be tested that does not contain iron, the water to be tested does not develop color due to the second agent, and therefore it can be determined that it does not contain iron.

  The second agent used in this iron content determination reagent is generally one that has substantially no reactivity with the first agent at room temperature. In this iron determination reagent, the first agent is, for example, at least one compound selected from the group consisting of hydroxylamine hydrochloride, hydroquinone, sodium thiosulfate, sodium pyrosulfite, hydrosulfite, and ascorbic acid, The second agent is, for example, from 4,7-diphenyl-1,10-phenanthroline disulfonic acid and its alkali metal salt and 2,4,6-tris (2-pyridyl) -1,3,5-triazine. One compound selected from the group consisting of

  Here, when the disodium salt of 4,7-diphenyl-1,10-phenanthroline disulfonic acid is used as the second agent, the first agent is selected from the group consisting of hydroxylamine hydrochloride, sodium thiosulfate and sodium pyrosulfite. It is preferable to use one of them. Further, when 2,4,6-tris (2-pyridyl) -1,3,5-triazine is used as the second agent, it is preferable to use hydroxylamine hydrochloride as the first agent. When the first agent and the second agent are combined as described above, an iron content determination reagent having good long-term storage stability can be obtained.

  The iron presence / absence determination method according to the present invention is a method for determining the presence / absence of iron in test water, a first agent for reducing trivalent iron ions to divalent iron ions, and a first agent; A step of adding a mixed reagent containing a second agent that reacts with divalent iron ions and develops color to the water to be tested; and for the test water to which the reagent is added, And a step of determining presence or absence.

In this determination method, when the above reagent is added to the test water containing only the iron content of the trivalent iron ion (Fe ³⁺ ) or the iron content of both the trivalent iron ion and the divalent iron ion (Fe ²⁺ ), Ions are reduced to divalent iron ions by the first agent. The divalent iron ions generated in this way and the divalent iron ions originally contained in the water under test react with the second agent to develop color. Thereby, it can be determined that the test water to which the reagent is added contains iron. Moreover, when the said reagent is added to the to-be-tested water containing only the iron content of a bivalent iron ion, the said divalent iron ion reacts with a 2nd agent and colors. Thereby, it can be determined that the test water to which the reagent is added contains iron. Furthermore, when the reagent is added to the water under test that does not contain iron, the water under test does not develop color due to the second agent, so it can be determined that it does not contain iron.

  The method for measuring the iron concentration according to the present invention is a method for measuring the iron concentration of water to be tested, and a first agent for reducing trivalent iron ions to divalent iron ions, and a mixture with the first agent A step of adding a predetermined amount of a reagent containing a second agent that develops color by reacting with divalent iron ions to a predetermined amount of water to be tested; And a step of measuring a color development amount by two agents.

When the above reagent is added to the test water containing only the iron content of the trivalent iron ion (Fe ³⁺ ) or the iron content of both the trivalent iron ion and the divalent iron ion (Fe ²⁺ ), the trivalent iron ion It is reduced to divalent iron ions by the agent. The divalent iron ions thus generated and the divalent iron ions originally contained in the water under test react with the second agent to develop a color and cause the test water to develop a color. Here, the color development amount of the water to be tested varies depending on the concentration of divalent iron ions contained in the water to be tested. That is, as the divalent iron ion concentration is lower, the color development amount is smaller, and as the divalent iron ion concentration is higher, the color development amount is larger. Therefore, when the color development amount of the test water by the second agent is measured, the iron concentration of the test water can be measured based on the magnitude.

  Since the reagent for determining iron content of the present invention is a mixture of the first agent and the second agent described above, the presence or absence of iron in the water under test can be easily and accurately simply added to the water under test. Can be determined.

  Since the method for determining the presence or absence of iron according to the present invention uses the reagent for determining iron content according to the present invention, the presence or absence of iron in the water to be tested can be easily and accurately determined by simply adding the reagent to the water to be tested. Can be determined.

  Since the method for measuring iron concentration according to the present invention uses the iron determination reagent of the present invention, the iron concentration of the water to be tested can be measured easily and accurately.

The reagent for determining iron content of the present invention is a mixture of a first agent that functions as an iron reducing agent and a second agent that functions as an iron coloring agent.
The first agent used here is for reducing trivalent iron ions to divalent iron ions, and various compounds having such a reducing action. Examples of such compounds include hydroxylamine hydrochloride, hydroquinone, sodium thiosulfate, sodium pyrosulfite, hydrosulfite, and ascorbic acid. These compounds can be used in a suitable mixture of two or more, as long as the object of the present invention is not impaired.

  On the other hand, the second agent reacts with divalent iron ions and develops color, and is a variety of compounds having such a color developing action. Examples of such compounds include o-phenanthroline, 4,7-diphenyl-1,10-phenanthroline disulfonic acid (DPP) and its alkali metal salt, 2,4,6-tris (2-pyridyl) -1 , 3,5-triazine (TPTZ), 2- (5-nitro-2-pyridylazo) -5- [Nn-propyl-N- (3-sulfopropyl) amino] phenol (Nitro-PAP) and its alkali Mention may be made of metal salts and 3- (2-pyridyl) -5,6-bis (4-sulfophenyl) -1,2,4-triazine (PDT) and its alkali metal salts. However, from the viewpoint of storage stability of the iron content determination reagent of the present invention, the second agent preferably has substantially no reactivity with the first agent at room temperature. Here, “normal temperature” means a temperature range of 5 to 50 ° C. A preferable second agent having such conditions is DPP or an alkali metal salt thereof or TPTZ when any one of the above-mentioned examples is used as the first agent.

  The iron content determination reagent of the present invention can be usually prepared by dissolving the first agent and the second agent in an appropriate amount of water and mixing them. Here, the first agent and the second agent may be mixed in advance and then dissolved in water, or one of the first agent and the second agent may be first dissolved in water and then the other may be further added. And may be dissolved. At this time, an acid such as hydrochloric acid may be added in order to increase the solubility of the first agent or the second agent in water. Further, when the second agent to be used is colored only in a specific pH range, a pH adjusting agent and a buffering agent for adjusting to the pH range can be mixed together.

  The mixing ratio of the first agent and the second agent can be appropriately set according to the use of the iron content determination reagent. For example, when qualitatively determining the presence or absence of iron in the water to be tested, which will be described later, depending on the amount of water to be tested, some of the trivalent iron ions that are expected to be contained in the water to be tested are divalent iron ions. The first agent in an amount that can be reduced to the amount of divalent iron ions that are reduced from trivalent iron ions and a portion of the divalent iron ions that are expected to be initially contained in the water under test. Mixing the two is sufficient. On the other hand, when quantitatively determining the iron content contained in the water under test (ie, when determining the iron concentration), all the trivalent iron ions expected to be contained in the water under test are divalent. The amount of the first agent that can be reduced to iron ions, the amount of divalent iron ions reduced from trivalent iron ions, and the amount of divalent iron ions expected to be initially contained in the test water It is necessary to mix with the second agent.

  Incidentally, the preferable mixing ratio of the first agent and the second agent is usually 10 to 100 parts by weight of the first agent with respect to 1 part by weight of the second agent.

The combination of the first agent and the second agent in the iron content determination reagent of the present invention is preferably in the following form.
Form 1
DPP disodium salt as the second agent and hydroxylamine hydrochloride, sodium thiosulfate or sodium pyrosulfite as the first agent. In this case, it is preferable to use 55 to 65 parts by weight of the first agent with respect to 1 part by weight of the second agent.
Form 2
One using TPTZ as the second agent and hydroxylamine hydrochloride as the first agent. In this case, it is preferable to use 15 to 25 parts by weight of the first agent with respect to 1 part by weight of the second agent.
These forms of the iron content determination reagent have good storage stability and can be stored for a long period of several months.

Next, a method of using the iron content determination reagent of the present invention will be described.
The iron content determination reagent of the present invention can be used to simply determine the presence or absence of iron in the water under test, in particular, the presence or absence of trace amounts of iron. Here, the water to be tested is, for example, various kinds of water such as tap water, industrial water, and groundwater, and is not particularly limited.

When determining the presence or absence of iron in the test water using the iron determination reagent of the present invention, an appropriate amount of the iron determination reagent is added to the test water. For example, an iron content determination reagent is added at a rate of 10 to 20 microliters per 1 milliliter of water to be tested. Here, when the above reagent is added to the test water containing only the iron content of the trivalent iron ion (Fe ³⁺ ) or the iron content of both the trivalent iron ion and the divalent iron ion (Fe ²⁺ ), the trivalent iron ion is , Reduced to divalent iron ions by the first agent. The divalent iron ions generated in this way and the divalent iron ions originally contained in the water under test react with the second agent to develop color. Further, when a reagent is added to the water to be tested containing only the iron content of the divalent iron ion, the divalent iron ion reacts with the second agent and develops color. On the other hand, when the reagent is added to the water under test that does not contain iron, the water under test does not develop color due to the second agent.

  For this reason, when the water to be tested to which the reagent is added is discolored (that is, when color is developed by the second agent), it can be determined that the water to be tested contains iron. On the other hand, when the test water does not change color (that is, when the second agent does not develop color), it can be determined that the test water does not contain iron. Incidentally, the presence or absence of coloration of the water to be tested can be determined visually, but various optical methods, for example, measurement of the change in the transmittance of the light irradiated to the water to be tested and the spectral spectrum of the water to be tested. It can also be determined by measuring.

  In addition, the iron content determination reagent of the present invention can also be used to determine the iron content concentration in the water to be tested. In this case, first, the relationship between the divalent iron ion concentration in water and the color development amount due to the reaction between the divalent iron ions and the second agent is examined in advance, and concentration determination data such as a calibration curve is created. Then, a predetermined amount of the iron determination reagent thus prepared is added to a predetermined amount of water to be tested. Specifically, an iron content determination reagent is added at a rate of 10 to 20 microliters per 1 milliliter of water to be tested. In this case, in the water to be tested to which the iron content determination reagent is added, the total amount of trivalent iron ions is reduced to divalent iron ions, and the divalent iron ions react with the second agent to develop a color, Color the test water. The color development amount of the test water varies depending on the divalent iron ion concentration in the test water. Specifically, the color development amount is small when the divalent iron ion concentration is low, and the color development amount is large when the divalent iron ion concentration is high. Therefore, when the color development amount of the water to be tested by the second agent is measured, the iron concentration can be determined based on the measurement result, that is, the color development amount based on the concentration measurement data.

  Here, the amount of color of the test water is usually determined by measuring the absorbance of the maximum absorption from various optical methods, for example, the method of measuring the transmittance of the light irradiated to the test water or the spectrum of the test water. It can be measured by a measuring method.

Examples 1-6
A disodium salt of DPP (hereinafter referred to as “DPPS”) was used as the second agent, and this was mixed with various first agents shown in Table 1 to prepare an iron content determination reagent. Here, the first agent and the second agent were dissolved in distilled water to prepare an iron content determination reagent. The amounts of the first agent, second agent and distilled water used are as shown in Table 1. The characteristics of DPPS used as the second agent are as follows.

◎ pH range capable of reacting with divalent iron ions: 2-9
◎ Maximum absorption in spectroscopic spectrum when colored by reaction with divalent iron ions: 535 nm
◎ Molar extinction coefficient: 22,400 M ⁻¹ cm ⁻¹

Examples 7-12
TPTZ was used as the second agent, and this was mixed with various first agents shown in Table 1 to prepare an iron content determination reagent. Here, the first agent and the second agent were dissolved in a 0.1 N hydrochloric acid aqueous solution to prepare an iron content determination reagent. The amounts of the first agent, the second agent and the 0.1 N hydrochloric acid aqueous solution used are as shown in Table 1. Moreover, the characteristics of TPTZ used as the second agent are as follows.

◎ pH range capable of reacting with divalent iron ions: 3.4 to 5.8
◎ Maximum absorption in spectral spectrum when colored by reacting with divalent iron ions: 595 nm
◎ Molar extinction coefficient: 23,000 M ⁻¹ cm ⁻¹

Evaluation 1 (determining whether iron is present)
An iron standard solution manufactured by Wako Pure Chemical Industries, Ltd. having a trivalent iron ion concentration of 100 mg / liter was diluted with distilled water to prepare test water having a trivalent iron ion concentration of 0.1 mg / liter. Then, 40 microliters of the iron content determination reagent of each example was added to 4 milliliters of the water to be tested. As a result, the test water to which the iron determination reagents of Examples 1 to 6 were respectively added changed to red, and the test water to which the iron determination reagents of Examples 7 to 12 were respectively added was The color changed to blue. Further, when 40 microliters of the iron content determination reagent of each example was added to 4 milliliters of distilled water, no discoloration was observed for any distilled water. According to these results, the presence or absence of iron in water can be easily determined using the iron content determination reagents of Examples 1-12.

Evaluation 2 (Measurement of iron concentration)
An iron standard solution manufactured by Wako Pure Chemical Industries, Ltd. with a trivalent iron ion concentration of 100 mg / liter is diluted with distilled water, and the trivalent iron ion concentrations are 0.05 mg / liter, 0.2 mg / liter and 0.5 mg. Three kinds of water to be tested, each set to 4 liters / liter, were prepared. Then, 40 microliters of the iron content determination reagent of each example was added to each of these test waters, and the color change at that time was examined by absorptiometry. A calibration curve prepared based on the spectrum at this time and the relationship between the absorbance at the maximum absorption wavelength in the spectrum and the trivalent iron ion concentration is shown in FIGS. Table 2 shows the correspondence between each embodiment and each figure.

According to FIGS. 1, 3, 5, 7, 9, and 11, the water to be tested to which the reagent for determining iron content of Examples 1 to 6 is added has a maximum absorption around 535 nm, It can be seen that the absorbance varies depending on the trivalent iron ion concentration (the higher the trivalent iron ion concentration, the larger the absorbance, and the lower the trivalent iron ion concentration, the smaller the absorbance). Then, according to FIG. 2, FIG. 4, FIG. 6, FIG. 8, FIG. 10 and FIG. 12, the calibrations created based on the spectral spectra of FIG. 1, FIG. 3, FIG. The line has a correlation coefficient (R ² ) of approximately 1 and is extremely reliable.

Moreover, according to FIG. 13, FIG. 15, FIG. 17, FIG. 19, FIG. 21 and FIG. 23, the test water to which the reagent for iron content determination of Examples 7 to 12 was added has a maximum absorption around 595 nm, It can also be seen that the absorbance varies depending on the trivalent iron ion concentration (the higher the trivalent iron ion concentration, the larger the absorbance, and the lower the trivalent iron ion concentration, the smaller the absorbance). And according to FIGS. 14, 16, 18, 20, 22, and 24, the calibrations created based on the spectral spectra of FIGS. 13, 15, 17, 19, 21, and 23, respectively. The line has a correlation coefficient (R ² ) of approximately 1 and is extremely reliable.

  From the above results, it can be seen that the iron content determination reagents of Examples 1 to 12 are useful for measuring the iron content concentration of the water under test.

Evaluation 3 (storage stability)
(About Examples 1-6)
The storage stability of the iron determination reagents of Examples 1 to 6 was examined. Here, an iron standard solution manufactured by Wako Pure Chemical Industries, Ltd. with a trivalent iron ion concentration of 100 mg / liter was diluted with distilled water to prepare test water with a trivalent iron ion concentration of 0.5 mg / liter. . Then, 40 microliters of the iron content determination reagent of Examples 1 to 6 was added to 4 ml of this water to be tested, and the absorbance at 535 nm was measured. The iron determination reagents used here are those immediately after preparation, those stored for 5 hours at 55 ° C., those stored for 25 hours at the same temperature, and those stored for 100 hours at the same temperature (except for Example 6). . The results are shown in FIGS. Table 3 shows the correspondence between Examples 1 to 6 and the figure. According to FIG. 25 to FIG. 30, the iron content determination reagents of Examples 1 to 5 have almost the same absorbance as those immediately after preparation and those stored for 100 hours, and have good storage stability.

  In addition, the iron content determination reagents of Examples 1 to 5 were examined for long-term storage stability in the same manner as described above. The results are shown in FIG. In FIG. 31, the molar extinction coefficient ratio on the vertical axis represents the ratio (measured value / theoretical value) of the molar extinction coefficient (measured value) of the second agent colored in the water under test to the theoretical value of the molar extinction coefficient of the second agent. The higher the numerical value, the better the storage stability of the iron content determination reagent.

  According to FIG. 31, the iron content determination reagents of Examples 1, 2 and 3 have good storage stability even when stored at 55 ° C. for 30 days, and are particularly excellent in terms of storage stability. I understand that.

(About Examples 7-12)
The storage stability of the iron content determination reagents of Examples 7 to 12 was examined. Here, an iron standard solution manufactured by Wako Pure Chemical Industries, Ltd. with a trivalent iron ion concentration of 100 mg / liter was diluted with distilled water to prepare test water with a trivalent iron ion concentration of 0.5 mg / liter. . And 40 microliters of the iron content determination reagents of Examples 7 to 12 were added to 4 ml of this water to be tested, and the absorbance at 595 nm was measured. The iron determination reagents used here were those immediately after preparation, those stored for 5 hours at 55 ° C., those stored for 25 hours at the same temperature, and those stored for 100 hours at the same temperature (except Examples 10 and 12). It is. The results are shown in FIGS. Table 4 shows the correspondence between Examples 7 to 12 and the figure. According to FIGS. 32 to 37, the iron content determination reagents of Examples 7, 9 and 11 do not substantially change in absorbance even after being stored for about 100 hours and have good storage stability.

  In addition, the iron content determination reagents of Examples 7, 9 and 11 were examined for long-term storage stability in the same manner as described above. The results are shown in FIG. In FIG. 38, the molar extinction coefficient ratio on the vertical axis has the same meaning as in FIG. According to FIG. 38, it can be seen that the iron content determination reagent of Example 7 has good storage stability even when stored at 55 ° C. for 30 days, and is particularly excellent in terms of storage stability.

The figure which shows the spectrum measured about the reagent of Example 1 in evaluation 2 of an Example. The figure which shows the calibration curve created about the reagent of Example 1 in evaluation 2 of an Example. The figure which shows the spectrum measured about the reagent of Example 2 in evaluation 2 of an Example. The figure which shows the calibration curve created about the reagent of Example 2 in evaluation 2 of an Example. The figure which shows the spectrum measured about the reagent of Example 3 in evaluation 2 of an Example. The figure which shows the analytical curve created about the reagent of Example 3 in evaluation 2 of an Example. The figure which shows the spectrum measured about the reagent of Example 4 in evaluation 2 of an Example. The figure which shows the analytical curve created about the reagent of Example 4 in evaluation 2 of an Example. The figure which shows the spectrum measured about the reagent of Example 5 in evaluation 2 of an Example. The figure which shows the calibration curve created about the reagent of Example 5 in evaluation 2 of an Example. The figure which shows the spectrum measured about the reagent of Example 6 in evaluation 2 of an Example. The figure which shows the analytical curve created about the reagent of Example 6 in evaluation 2 of an Example. The figure which shows the spectral spectrum measured about the reagent of Example 7 in evaluation 2 of an Example. The figure which shows the analytical curve created about the reagent of Example 7 in evaluation 2 of an Example. The figure which shows the spectral spectrum measured about the reagent of Example 8 in evaluation 2 of an Example. The figure which shows the analytical curve created about the reagent of Example 8 in evaluation 2 of an Example. The figure which shows the spectral spectrum measured about the reagent of Example 9 in evaluation 2 of an Example. The figure which shows the analytical curve created about the reagent of Example 9 in evaluation 2 of an Example. The figure which shows the spectral spectrum measured about the reagent of Example 10 in evaluation 2 of an Example. The figure which shows the calibration curve created about the reagent of Example 10 in evaluation 2 of an Example. The figure which shows the spectrum measured about the reagent of Example 11 in evaluation 2 of an Example. The figure which shows the analytical curve created about the reagent of Example 11 in evaluation 2 of an Example. The figure which shows the spectral spectrum measured about the reagent of Example 12 in evaluation 2 of an Example. The figure which shows the analytical curve created about the reagent of Example 12 in evaluation 2 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 1 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 2 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 3 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 4 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 5 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 6 in evaluation 3 of an Example. The figure which shows the result of having investigated the long-term storage stability about the reagent of Examples 1-5 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 7 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 8 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 9 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 10 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 11 in evaluation 3 of an Example. The figure which shows the result of having investigated the storage stability about the reagent of Example 12 in evaluation 3 of an Example. The figure which shows the result of having investigated the long-term storage stability about the reagent of Example 7, 9 and 10 in evaluation 3 of an Example.

Claims (7)

A reagent for determining the presence or absence of iron in the water under test,
A first agent for reducing trivalent iron ions to divalent iron ions;
A second agent that mixes with the first agent and develops color by reacting with divalent iron ions;
A reagent for determining iron content.   The reagent for iron content determination according to claim 1, wherein the second agent has substantially no reactivity with the first agent at room temperature.   The first agent is at least one compound selected from the group consisting of hydroxylamine hydrochloride, hydroquinone, sodium thiosulfate, sodium pyrosulfite, hydrosulfite and ascorbic acid, and the second agent is 4,7- A compound selected from the group consisting of diphenyl-1,10-phenanthroline disulfonic acid and alkali metal salts thereof and 2,4,6-tris (2-pyridyl) -1,3,5-triazine. Item 3. The reagent for determining iron content according to Item 1 or 2.   A disodium salt of 4,7-diphenyl-1,10-phenanthroline disulfonic acid is used as the second agent, and one selected from the group consisting of hydroxylamine hydrochloride, sodium thiosulfate and sodium pyrosulfite as the first agent. The reagent for iron content determination according to claim 3, wherein one is used.   The iron determination reagent according to claim 3, wherein 2,4,6-tris (2-pyridyl) -1,3,5-triazine is used as the second agent, and hydroxylamine hydrochloride is used as the first agent. A method for determining the presence or absence of iron in the water under test,
A reagent comprising a first agent for reducing trivalent iron ions to divalent iron ions, and a second agent mixed with the first agent that develops color by reacting with the divalent iron ions, Adding to, and
A step of determining the presence or absence of coloration by the second agent for the water to be tested to which the reagent is added;
Method for determining the presence or absence of iron containing iron. A method for measuring the iron concentration of water under test,
A predetermined amount of a reagent comprising a first agent for reducing trivalent iron ions to divalent iron ions and a second agent mixed with the first agent to develop color by reacting with divalent iron ions is provided. Adding to a fixed amount of the test water;
Measuring the color development amount by the second agent for the water to be tested to which the reagent is added;
Of measuring iron concentration including

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