Method for storing liquid composition

Abstract

To provide a liquid composition in which sedimentation is inhibited from occurring.SOLUTION: The liquid composition of the present disclosure contains an alkali metal sulfide and has a yellow index of 10.00 or lower.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a liquid composition, a method for producing a liquid composition, and a method for storing a liquid composition. [Background technology]

[0002] Sodium hydrogen sulfide is widely used as a catalyst, a sulfur source, etc. Sodium hydrogen sulfide is sometimes extracted from waste liquid generated in chemical plants, etc. For example, Patent Document 1 discloses a method for recovering an alkaline solution containing sodium hydrogen sulfide from waste soda solution, etc., in which fine sulfides contained in the alkaline solution are removed and separated by coagulating and settling them with polyacrylamide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 58-172204 Summary of the Invention [Problem to be solved by the invention]

[0004] Sodium hydrogen sulfide is often used in liquid form after being separated and freed from sediments, as in the past. However, during storage of a liquid composition containing sodium hydrogen sulfide, precipitation may occur in the liquid composition, resulting in the formation of solid matter. If the liquid composition is used as a raw material for a product while the solid matter has formed in the liquid composition, the solid matter may clog piping and a liquid transfer pump in the production line, thereby interfering with stable operation of the production line. On the other hand, it is conceivable to use the liquid composition after removing the solid matter from the liquid composition, but removing the solid matter is time-consuming. Therefore, there is a demand for a liquid composition in which the occurrence of precipitation itself is suppressed.

[0005] An object of one aspect of the present disclosure is to provide a liquid composition in which the occurrence of precipitation is suppressed, a method for producing a liquid composition, and a method for storing a liquid composition.

[0006] The means for solving the above problems include the following embodiments. <1> A liquid composition containing an alkali metal sulfide and having a yellow index of 10.00 or less. <2> The above-mentioned further contains an alkali metal sulfite. <1> The liquid composition according to claim 1. <3> the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol % or more; <2> The liquid composition according to claim 1. <4> Contains an alkali metal sulfide and an alkali metal sulfite, A liquid composition, wherein the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol % or more. <5> The alkali metal sulfite includes sodium sulfite. <2> ~ <4> The liquid composition according to any one of the above. <6> The alkali metal sulfide includes sodium hydrogen sulfide. <1> ~ <5> The liquid composition according to any one of the above. <7> The above further contains water. <1> ~ <6> The liquid composition according to any one of the above. <8> Contains alkali metal sulfide, alkali metal sulfite, and water, the total content of the alkali metal sulfide, the alkali metal sulfite, and the water is 90% by mass or more relative to the liquid composition; <1> ~ <7> The liquid composition according to any one of the above. <9> A method for producing a liquid composition containing an alkali metal sulfide and an alkali metal sulfite, comprising: A method for producing a liquid composition, comprising the step of adjusting the molar ratio of the alkali metal sulfite to the alkali metal sulfide to be 1.0 mol % or more. <10> A method for storing a liquid composition, comprising the step of adding an alkali metal sulfite to a liquid composition containing an alkali metal sulfide. <11> In the adding step, the alkali metal sulfite is added to the liquid composition so that the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol % or more. <10> A method for storing the liquid composition described in 1. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, there are provided a liquid composition in which the occurrence of precipitation is suppressed, a method for producing a liquid composition, and a method for storing a liquid composition. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0009] (1) First embodiment The liquid composition according to the first embodiment of the present disclosure contains an alkali metal sulfide and has a yellow index (hereinafter sometimes referred to as "YI") of 10.00 or less.

[0010] In the present disclosure, the term "alkali metal sulfide" refers to a compound in which at least one hydrogen atom of hydrogen sulfide is substituted with an alkali metal atom.

[0011] The liquid composition according to the first embodiment has the above-mentioned structure, and therefore the occurrence of precipitation is suppressed. The reason for the above effect is presumed to be as follows, but is not limited to this. Conventionally, the yellow index of aqueous sodium hydrogen sulfide solutions using commercially available sodium hydrogen sulfide (hereinafter referred to as "commercial products") is over 10.00, and the commercial products have a yellowish tint. The yellowish tint is thought to be due to sulfur-based ions dissolved in the commercial products. Sulfur-based ions include sulfide ions (S 2- ) is included. The present inventors have confirmed that black solids may occur in a commercially available product when the product is stored. The inventors then analyzed the black solids and found that they are iron sulfide (FeS). From these analysis results, it is believed that the commercially available product contains iron ions, and that the occurrence of precipitation is due to iron ions dissolved in the commercially available product and sulfur-based ions dissolved in the commercially available product. It is believed that the iron ions dissolved in the commercially available product are inevitably mixed in during the manufacturing process of sodium hydrogen sulfide, etc. A liquid composition having a yellow index of 10.00 or less indicates that the amount of sulfur-based ions dissolved in the liquid composition is smaller than in the past. Therefore, even if iron ions are dissolved in the liquid composition, the reaction in which the iron ions dissolved in the liquid composition react with the sulfur-based ions dissolved in the liquid composition to produce iron sulfide (FeS) (hereinafter referred to as the "iron sulfide production reaction") is less likely to proceed than in the past. As a result, it is presumed that the occurrence of precipitation is suppressed in the liquid composition according to the first embodiment.

[0012] In the present disclosure, the term "precipitation" refers to a phenomenon in which a reaction product becomes a solid, such as a particulate, and precipitates in a liquid composition.

[0013] (1.1) Yellow Index In the first embodiment, the yellow index of the liquid composition is 10.00 or less, which suppresses the progress of the iron sulfide-producing reaction more than conventionally, and suppresses the occurrence of precipitation. The upper limit of the yellow index of the liquid composition is more preferably 8 or less, and even more preferably 7 or less, from the viewpoint of further suppressing the occurrence of precipitation. The lower limit of the yellow index of the liquid composition is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more. The yellow index of the liquid composition can be measured in the same manner as described in the examples.

[0014] An example of a method for adjusting the yellow index of the liquid composition to fall within the above range is to add an alkali metal sulfite to the liquid composition.

[0015] (1.2) Ingredients The liquid composition contains an alkali metal sulfide.

[0016] (1.2.1) Alkali metal sulfides Examples of alkali metal sulfides include alkali metal hydrogen sulfide salts, alkali metal sulfide salts, etc. Examples of alkali metal hydrogen sulfide salts include lithium hydrogen sulfide, sodium hydrogen sulfide, potassium hydrogen sulfide, rubidium hydrogen sulfide, cesium hydrogen sulfide, etc. Examples of alkali metal sulfide salts include sodium sulfide, potassium sulfide, etc. Among these, the alkali metal sulfide preferably contains sodium hydrogen sulfide, from the viewpoint of more appropriately suppressing the occurrence of precipitation.

[0017] The content of the alkali metal sulfide is not particularly limited and may be appropriately selected depending on the application of the alkali metal sulfide, etc. The upper limit of the content of the alkali metal sulfide relative to the liquid composition is preferably 60 mass % or less, more preferably 50 mass % or less, and even more preferably 30 mass % or less, from the viewpoint of further suppressing the occurrence of precipitation. The lower limit of the content of the alkali metal sulfide may be appropriately determined depending on the purpose, and is, for example, preferably 5% by mass or more, and more preferably 10% by mass or more, relative to the liquid composition. The mass of the alkali metal sulfide in the liquid composition is measured in accordance with JIS K1435 (1986).

[0018] (1.2.2) Alkali metal sulfites In the first embodiment, the liquid composition preferably further contains an alkali metal sulfite, which further suppresses the occurrence of precipitation. The reason for the above effect is presumed to be as follows, but is not limited to this. When the liquid composition contains an alkali metal sulfite, sulfur-based ions dissolved in the liquid composition react with the alkali metal sulfite to produce, for example, an alkali metal thiosulfate. In other words, the sulfur-based ions dissolved in the liquid composition are consumed in the reaction with the alkali metal sulfite, and the amount of sulfur-based ions dissolved in the liquid composition decreases. Therefore, even if iron ions are dissolved in the liquid composition, the reaction to produce iron sulfide is less likely to proceed. As a result, it is believed that the occurrence of precipitation is further suppressed.

[0019] In the present disclosure, the term "alkali metal sulfite" refers to a compound in which the hydrogen atom of sulfite is substituted with an alkali metal atom.

[0020] Examples of alkali metal sulfites include lithium sulfite, sodium sulfite, potassium sulfite, rubidium sulfite, and cesium sulfite. Among these, the alkali metal sulfite preferably contains sodium sulfite, since this is more suitable for suppressing the occurrence of precipitation.

[0021] (1.2.3) Molar ratio of alkali metal sulfite The molar ratio of the alkali metal sulfite to the alkali metal sulfide (hereinafter sometimes simply referred to as the "molar ratio of the alkali metal sulfite") is not particularly limited, but is preferably 1.0 mol % or more, which further suppresses the occurrence of precipitation. The reason for the above effect is presumed to be as follows, but is not limited to this. When the molar ratio of the alkali metal sulfite is 1.0 mol % or more, most of the sulfur-based ions dissolved in the liquid composition are consumed by reaction with the alkali metal sulfite. In other words, the amount of sulfur-based ions dissolved in the liquid composition is reduced. This makes it even more difficult for the iron sulfide-forming reaction to proceed. As a result, it is presumed that the occurrence of precipitation is further suppressed. The upper limit of the molar ratio of alkali metal sulfite to alkali metal sulfide may be appropriately set depending on the purpose, and is, for example, more preferably 10 mol % or less, and even more preferably 5 mol % or less. The lower limit of the molar ratio of alkali metal sulfite to alkali metal sulfide is preferably 1.2 mol % or more, more preferably 1.5 mol % or more, from the viewpoint of suitability for suppressing the occurrence of precipitation.

[0022] The content of the alkali metal sulfite is not particularly limited and is appropriately selected depending on the content of the alkali metal sulfide, etc. From the viewpoint of solubility, the upper limit of the content of the alkali metal sulfite is preferably 5% by mass or less, and more preferably 3% by mass or less, relative to the liquid composition. The lower limit of the content of the alkali metal sulfite is preferably 0.7% by mass or more, and more preferably 1.0% by mass or more, relative to the liquid composition, from the viewpoint of being more suitable for suppressing the occurrence of precipitation. The method for measuring the mass of the alkali metal sulfite in the liquid composition is the same as the method described in the Examples.

[0023] (1.2.4) Water The liquid composition preferably further contains water. The content of water is not particularly limited and may be appropriately selected depending on the intended use of the liquid composition. The upper limit of the water content may be appropriately set depending on the purpose, and is, for example, preferably 99% by mass or less, more preferably 90% by mass or less, based on the liquid composition. The lower limit of the water content is preferably 40% by mass or more, and more preferably 50% by mass or more, based on the liquid composition, from the viewpoint of the solubility of alkali metal sulfides, alkali metal sulfites, and the like.

[0024] When the liquid composition contains an alkali metal sulfide, an alkali metal sulfite, and water, the total content ratio of the alkali metal sulfide, the alkali metal sulfite, and the water (hereinafter sometimes simply referred to as the "total content ratio") is not particularly limited, and is preferably 90 mass% or more relative to the liquid composition. The upper limit of the total content may be set appropriately depending on the purpose, and is preferably 99% by mass or less, for example. The lower limit of the total content may be set appropriately depending on the purpose, and is, for example, more preferably 95% by mass or more, and even more preferably 97% by mass or more.

[0025] (1.3) Purpose The liquid composition can be used, for example, as a catalyst, a sulfur source, etc.

[0026] (2) Second embodiment The liquid composition according to the second embodiment contains an alkali metal sulfide and an alkali metal sulfite, and the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol % or more.

[0027] The liquid composition according to the second embodiment has the above-mentioned structure, and therefore the occurrence of precipitation is suppressed. The reason for the above effect is presumed to be as follows, but is not limited to this. As described above, when the molar ratio of the alkali metal sulfite is 1.0 mol % or more, the amount of sulfur-based ions dissolved in the liquid composition is extremely small. This makes it even more difficult for the iron sulfide-producing reaction to proceed. As a result, it is presumed that the occurrence of precipitation is suppressed.

[0028] (2.1) Yellow Index In the second embodiment, the yellow index of the liquid composition is not particularly limited, but is preferably 10.00 or less, which further suppresses the occurrence of precipitation. The reason for the above effect is presumed to be as follows, but is not limited to this. As described above, a liquid composition having a yellow index of 10.00 or less indicates that the amount of sulfur-based ions dissolved in the liquid composition is smaller than in the past. As a result, it is presumed that the progress of the iron sulfide-forming reaction is more suppressed than in the past, and the occurrence of precipitation is further suppressed. Preferable upper and lower limits of the yellow index of the liquid composition are the same as those exemplified as the preferable upper and lower limits of the yellow index of the liquid composition in the first embodiment. The yellow index of the liquid composition can be measured in the same manner as described in the examples.

[0029] Methods for adjusting the yellow index of the liquid composition to fall within the above range include the same methods as those exemplified as methods for adjusting the yellow index of the liquid composition in the first embodiment.

[0030] (2.2) Ingredients In a second embodiment, the liquid composition contains an alkali metal sulfide and an alkali metal sulfite.

[0031] (2.2.1) Molar ratio of alkali metal sulfite In the second embodiment, the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol % or more, which suppresses the occurrence of precipitation. The reason why the above effect is achieved is presumed to be the same as the reason why the effect is achieved by setting the molar ratio of the alkali metal sulfite to 1.0 mol % or more in the first embodiment, but is not limited to this. Preferable upper and lower limits of the molar ratio of the alkali metal sulfite are the same as those exemplified as the preferable upper and lower limits of the molar ratio of the alkali metal sulfite to the alkali metal sulfide in the liquid composition in the first embodiment.

[0032] (2.2.2) Alkali metal sulfides Examples of the alkali metal sulfide include the same ones as those exemplified as the alkali metal sulfide in the first embodiment. Among these, the alkali metal sulfide preferably contains sodium sulfite, from the viewpoint of further suppressing the occurrence of precipitation. The content ratio of the alkali metal sulfide is not particularly limited, and may be the same as the exemplified content ratio of the alkali metal sulfide in the first embodiment. The method for measuring the mass of the alkali metal sulfide in the liquid composition is the same as the method for measuring the mass of the alkali metal sulfide in the liquid composition in the first embodiment.

[0033] (2.2.3) Alkali metal sulfites Examples of the alkali metal sulfite include the same ones as those exemplified as the alkali metal sulfite in the first embodiment. Among these, the alkali metal sulfite preferably contains sodium hydrogen sulfide, from the viewpoint of further suppressing the occurrence of precipitation. The content of the alkali metal sulfite is not particularly limited, and may be the same as the content of the alkali metal sulfite exemplified in the first embodiment. The method for measuring the mass of the alkali metal sulfite in the liquid composition is the same as the method for measuring the mass of the alkali metal sulfite in the liquid composition in the first embodiment.

[0034] (2.2.4) Water The liquid composition preferably further contains water. The content of water is not particularly limited, and may be the same as the content of water exemplified in the first embodiment.

[0035] When the liquid composition contains an alkali metal sulfide, an alkali metal sulfite, and water, it is preferable that the total content of the alkali metal sulfide, the alkali metal sulfite, and the water is 90 mass% or more relative to the liquid composition. The total content ratio may be the same as the ratio exemplified as the total content ratio in the first embodiment.

[0036] (2.3) Application The liquid composition can be used, for example, as a catalyst, a sulfur source, etc.

[0037] (3) Method for producing liquid composition The method for producing a liquid composition according to the present disclosure is a method for producing a liquid composition containing an alkali metal sulfide and an alkali metal sulfite, and includes a preparation step (hereinafter referred to as the "preparation step") described below. As a result, the liquid composition according to the first embodiment or the liquid composition according to the second embodiment is obtained.

[0038] (3.1) Preparation process In the preparation step, the molar ratio of the alkali metal sulfite to the alkali metal sulfide is adjusted to 1.0 mol % or more.

[0039] (3.1.1) Preparation The method for adjusting the molar ratio of the alkali metal sulfite to 1.0 mol% or more is not particularly limited, and examples thereof include a method in which the mass of the alkali metal sulfide and the mass of the alkali metal sulfite in the liquid composition are measured, and based on these measured values, the alkali metal sulfite is added to the liquid composition containing the alkali metal sulfide so that the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol% or more. The molar ratio of the alkali metal sulfite to be prepared is not particularly limited as long as it is 1.0 mol % or more. The upper limit of the molar ratio of the alkali metal sulfite to be prepared is more preferably 10 mol % or less, and even more preferably 5 mol % or less, from the viewpoint of solubility. The lower limit of the molar ratio of the alkali metal sulfite to be prepared is more preferably 1.2 mol % or more, and even more preferably 1.5 mol % or more, from the viewpoint of further suppressing the occurrence of precipitation.

[0040] (3.1.2) Alkali metal sulfides Examples of the alkali metal sulfide in the method for producing a liquid composition of the present disclosure include the same ones as those exemplified as the alkali metal sulfides in the first embodiment, and preferred examples of the alkali metal sulfides include the same ones as in the first embodiment. The content ratio of the alkali metal sulfide is not particularly limited, and may be the same as the exemplified content ratio of the alkali metal sulfide in the first embodiment.

[0041] (3.1.3) Alkali metal sulfites Examples of the alkali metal sulfite include the same ones as those exemplified as the alkali metal sulfite in the first embodiment, and preferred alkali metal sulfites are also the same as those in the first embodiment. The content of the alkali metal sulfite is not particularly limited, and may be the same as the content of the alkali metal sulfite exemplified in the first embodiment.

[0042] (4) Storage method of the liquid composition The method for storing the liquid composition of the present disclosure includes the step of adding (hereinafter referred to as the "adding step") described below. This makes it possible to suppress the occurrence of precipitation in the liquid composition containing the alkali metal sulfide.

[0043] (4.1) Addition process In the adding step, an alkali metal sulfite is added to a liquid composition containing an alkali metal sulfide.

[0044] (4.1.1) Addition The method for adding the alkali metal sulfite to the liquid composition containing the alkali metal hydrogen chloride (hereinafter referred to as the "addition method") is not particularly limited, and may be any known method.

[0045] A preferred method of addition is to add the alkali metal sulfite to the liquid composition so that the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol % or more. Specifically, the addition method may involve measuring the mass of the alkali metal sulfide and the mass of the alkali metal sulfite in the liquid composition, and adding the alkali metal sulfite to the liquid composition containing the alkali metal sulfide based on these measured values ​​so that the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol % or more. This makes it possible to suppress the occurrence of precipitation in the liquid composition containing the alkali metal sulfide. The upper and lower limits of the molar ratio of the alkali metal sulfite to be prepared are the same as the preferred upper and lower limits of the molar ratio of the alkali metal sulfite to the alkali metal sulfide in the method for producing the liquid composition of the present disclosure.

[0046] (4.1.2) Alkali metal sulfides Examples of the alkali metal sulfide include the same ones as those exemplified as the alkali metal sulfide in the first embodiment, and preferred alkali metal sulfides are also the same as those in the first embodiment. The content ratio of the alkali metal sulfide is not particularly limited, and may be the same as the exemplified content ratio of the alkali metal sulfide in the first embodiment.

[0047] (4.1.3) Alkali metal sulfites Examples of the alkali metal sulfite include the same ones as those exemplified as the alkali metal sulfite in the first embodiment, and preferred alkali metal sulfites are also the same as those in the first embodiment. The content of the alkali metal sulfite is not particularly limited, and may be the same as the content of the alkali metal sulfite exemplified in the first embodiment. [Example]

[0048] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. In the following description, "parts" and "%" are by mass unless otherwise specified.

[0049] [Sodium sulfite analysis method] The mass of sodium sulfite in the liquid composition was determined by measurement in accordance with JIS K1435 (1986).

[0050] [Water-based Yellow Index Measurement Method] The yellow index of the liquid composition was measured under the following conditions: <Measurement conditions> Equipment: Konica Minolta's "SPECTROPHOTOMETER CM-5" Measurement mode: E313-96 Quartz cell: 20mm

[0051] [Example 1] The sodium hydrogen sulfide in the glass beaker was diluted with pure water so that the sodium hydrogen sulfide content was 26.0 mass% relative to the sodium hydrogen sulfide aqueous solution (hereinafter referred to as "26 mass% sodium hydrogen sulfide aqueous solution"). Thus, a 26 mass% sodium hydrogen sulfide aqueous solution was obtained. The presence of iron in the 26 mass % aqueous sodium hydrogen sulfide solution was confirmed using an ICP-MS Agilent7500cs (manufactured by Agilent Technologies). A liquid composition was prepared by adding sodium sulfite (Na2SO3) to 50 g of a 26 mass% aqueous solution of sodium hydrogen sulfide (molar number of NaSH: 0.232 mol) so that the content of sodium sulfite (Na2SO3) was 1.0 mass% (molar number of Na2SO3: 0.004 mol) relative to the liquid composition, and stirring to completely dissolve the sodium sulfite. The resulting liquid composition was colorless and transparent. The mass of sodium sulfite in the obtained liquid composition was measured by the sodium sulfite analysis method. The yellow index of the liquid composition was measured by the aqueous solution yellow index measurement method. The measurement results are shown in Table 1.

[0052] [Examples 2 to 3, Comparative Example 1] Liquid compositions were prepared in the same manner as in Example 1, except that the content of sodium sulfite was changed as shown in Table 1. The liquid compositions in Examples 2 and 3 were colorless and transparent, whereas the liquid composition in Comparative Example 1 was yellowish in color. The mass of sodium sulfite in the liquid composition and the yellow index of the liquid composition were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0053] [Storage stability evaluation] The liquid composition was stored in an oven at 40°C for two weeks. After two weeks had passed since the liquid composition was stored in the oven, the presence or absence of precipitate in the liquid composition was evaluated visually according to the following evaluation criteria. The evaluation results are shown in Table 1.

[0054] A: No solid matter, including black solid matter, was visually observed in the liquid composition. B: It was visually confirmed that solid precipitates including particulate black solid matter were spread across the entire bottom surface of the liquid composition.

[0055] [Table 1]

[0056] The liquid composition of Comparative Example 1 contains sodium hydrogen sulfide. The yellow index of the liquid composition of Comparative Example 1 was 28.20, which was not 10.00 or less. Therefore, the storage stability of the liquid composition of Comparative Example 1 was evaluated as "B." This indicates that the occurrence of precipitation is not suppressed in the liquid composition of Comparative Example 1. In contrast, the liquid compositions of Examples 1 to 3 contain sodium hydrogen sulfide. The yellow index of the liquid compositions of Examples 1 to 3 was 6.87 or less, and 10.00 or less. Therefore, the storage stability of the liquid compositions of Examples 1 to 3 was evaluated as "A." As a result, it was found that the occurrence of precipitation was suppressed in the liquid compositions of Examples 1 to 3.

[0057] The liquid composition of Comparative Example 1 contained sodium hydrogen sulfide and sodium sulfite. The molar ratio of sodium sulfite to sodium hydrogen sulfide (Na2SO3 / NaSH) was 0.9 mol%, which was not 1.0 mol% or more. Therefore, the storage stability of the liquid composition of Comparative Example 1 was evaluated as "B." This indicated that the liquid composition of Comparative Example 1 did not suppress the occurrence of precipitation. In contrast, the liquid compositions of Examples 1 to 3 contain sodium hydrogen sulfide and sodium sulfite. The molar ratio of sodium sulfite to sodium hydrogen sulfide (Na2SO3 / NaSH) was 1.7 mol% or more, and 1.0 mol% or more. Therefore, the storage stability of the liquid compositions of Examples 1 to 3 was evaluated as "A." As a result, it was found that the occurrence of precipitation was suppressed in the liquid compositions of Examples 1 to 3.

[0058] In the storage stability evaluation, the black solid generated in the liquid composition of Comparative Example 1 was analyzed by X-ray analysis, and it was found that the black solid was iron sulfide (FeS). This revealed that the iron source of the black solid was derived from the raw material products of sodium hydrogen sulfide or sodium sulfite.

Claims

[Claim 1] The method includes adding an alkali metal sulfite to a liquid composition containing an alkali metal sulfide, A method for storing a liquid composition, wherein in the adding step, the alkali metal sulfite is added to the liquid composition so that the molar ratio of the alkali metal sulfite to the alkali metal sulfide is 1.0 mol % or more.

Images