Production process for preparing potassium sulfate from glauberite by asymmetric equilibrium method

Abstract

The invention discloses a production process for preparing potassium sulfate from glauberite by an asymmetric balance method, which is characterized in that two asymmetries are designed, one is that an evaporation system adopts a mode of feeding more cold clear liquid and discharging more salt mother liquid, evaporation is carried out according to a fixed proportion, enough evaporation condensate water can be evaporated in unit time, and the evaporation efficiency is improved; the excessive part is used for digesting water from an external supplementing system; secondly, the secondary conversion reaction is a reaction of a potassium chloride solution and glauberite in an equal proportion, the glauberite containing the glauberite is matched with anhydrous sodium sulphate to produce potassium sulfate, and the core is that the potassium index of a primary conversion reaction system is controlled by using the proportion of the glauberite containing the glauberite, so that the production quantity of the glauberite is adjusted; the potassium sulfate is matched with the evaporation and condensation water amount consumed due to equal-proportion dissolution, so that the overall balance is maintained for production, and meanwhile, the quality of the prepared potassium sulfate meets the quality requirements of agricultural potassium sulfate national standard GB / T 20406-2017 powder crystalline superior products (K2O is greater than or equal to 52%) and first-grade products (K2O is greater than or equal to 50%).

Description

Technical Field

[0001] The present invention relates to the technical field of potassium sulfate production process by mirabilite method, and specifically relates to a production process for preparing potassium sulfate by an asymmetric balancing method of potassium-containing mirabilite. Background Art

[0002] At present, there are mainly three domestic production processes for potassium sulfate: one is the Mannheim method for potassium sulfate production process, in which potassium chloride reacts with sulfuric acid in a Mannheim furnace at a high temperature (500 - 600 °C) to obtain potassium sulfate finished products. The generated HC1 gas is absorbed by a tail gas recovery device to obtain by-product hydrochloric acid. This process causes relatively serious corrosion to equipment, has relatively large environmental protection risks, and at the same time, the sales of by-product hydrochloric acid directly affect the production of potassium sulfate. The obtained finished potassium sulfate contains free acid and relatively high chloride due to the reaction under acidic conditions. The second is the ammonium sulfate method for potassium sulfate production process, and the disposal of by-product ammonium chloride affects potassium sulfate production. The third is the resource-based method, which directly separates and extracts from salt lakes. The products have more impurities and the exploitation of salt lakes is restricted.

[0003] The method for producing potassium sulfate by converting mirabilite (Na2SO4·10H2O) is to react mirabilite with potassium chloride to first form potassium mirabilite (Na2SO4·3K2SO4) and a first mother liquor (also called potassium mirabilite mother liquor), see the following formula (1), and then further react the separated potassium mirabilite with potassium chloride to produce potassium sulfate and sodium chloride, see the following formulas (2) and (3). The technological process of producing potassium sulfate through separation and drying. The theoretical basis for producing potassium sulfate by mirabilite conversion method is the K + 、Na + / / Cl - 、SO4 2- —H2O quaternary water-salt system phase diagram. According to the differences in the solubility of various salts at different temperatures, crystallization separation is carried out. KCl, NaCl, K2SO4, and Na2SO4 are four salts that form a quaternary water-salt system with water. Among them, NaCl and K2SO4, and Na2SO4 and KCl are salt pairs. At any temperature, the crystallization regions of potassium sulfate and sodium chloride do not adjoin each other. Therefore, potassium chloride and sodium sulfate must go through two-stage conversion to produce potassium sulfate.

[0004] The chemical reactions are as follows:

[0005] Na2SO4 + KCl + H2O → Na2SO4·3K2SO4 + a first mother liquor (also called potassium mirabilite mother liquor) (1)

[0006] Na2SO4·3K2SO4 + KCl + H2O → K2SO4 + a second mother liquor (also called potassium mother liquor) (2)

[0007] The first mother liquor → NaCl + salt mother liquor + H2O (3)

[0008] The main raw materials for producing potassium sulfate by the Glauber's salt conversion method are Glauber's salt, potassium chloride, and water, and the entire production system is in a closed cycle. The water entering the system mainly includes the evaporated condensed water added by the second conversion of dissolved potassium chloride and the crystallized water brought in by the raw material Glauber's salt; the water flowing out of the system is mainly distilled water. In theory, only when the two are balanced can the entire system operate stably. In the production practice process, the water entering the system also includes process wastewater recovered from production operations, spray water, machine seal water, cooling tower water, flushing water, etc. supplemented by the outside world. The water balance is difficult to maintain, and the system liquid level continues to expand. At that time, emergency measures can only be taken to increase the evaporation intensity to lower the liquid level of the system, which will reduce the quality of the potassium sulfate product. Therefore, the development of a production process for preparing potassium sulfate by an asymmetric equilibrium method containing potassium Glauber's salt is a technical problem to be solved in the present invention. Summary of the invention

[0009] The purpose of the present invention is to solve the problems that in the actual production process of preparing potassium sulfate from mirabilite, the water balance is difficult to maintain, the system liquid level continues to expand, and emergency measures can only be taken to increase the evaporation intensity to lower the system liquid level, but the quality of the potassium sulfate product will be reduced. A production process for preparing potassium sulfate by an asymmetric equilibrium method containing potassium mirabilite is provided.

[0010] To achieve the above object, the present invention is implemented by the following technical solutions:

[0011] The present invention provides a production process for preparing potassium sulfate by an asymmetric equilibrium method containing sodium sulfate, comprising the following steps:

[0012] (1) According to the material balance calculation at 25° C., thenardite, potassium chloride and water are added in proportion to react to obtain a first-turn mother liquor and glauberite, and the glauberite enters the second turn to participate in the reaction; after the first-turn mother liquor is subjected to plate and frame filter pressing to remove impurities, condensed water is evaporated at a temperature of 100° C. at a ratio of 30-35% of the total volume of the system to obtain salt and salt mother liquor, the salt mother liquor is subjected to n-stage flash evaporation to obtain a salt mother liquor with a low water content index, and the salt mother liquor is cooled to 50-60° C. and then enters the front end of the first turn reaction for recycling. ; The water index of the mother liquor in the front end reaction tank of the first reaction is 14-15; the temperature of the mother liquor in the middle reaction tank of the first reaction is 25-35°C, the water index is 14-15, the temperature of the mother liquor in the reaction tank at the end of the first reaction is 25-35°C, the water index is 15-16; the first reaction is n series-connected reaction tanks with self-circulation and lower circulation, stirring and coil cooling, n≥6, the volume of the reaction tank V=100-120m 3 , the material is continuously self-circulated and down-circulated through the circulation pump;

[0013] In the present invention, the functional areas of the first-stage reaction are partitioned. No additional water is added to the reaction tank in the first half, and the water index of the mother liquor at the front end of the first stage is controlled to be 14 - 15. The quality of the glaserite generated is controlled in the reaction tank in the second half, and the Cl remaining in the glaserite - ≤3%.

[0014] (2) Dissolve potassium chloride in the condensed water obtained in step (1) to obtain a potassium chloride solution. The mass fraction of potassium chloride in the potassium chloride solution is 24% - 26%. Perform a second-stage reaction on the potassium chloride solution and the glaserite obtained in step (1). The potassium chloride solution is controlled by a flowmeter to obtain potassium sulfate and a mother liquor of the second stage. The mother liquor of the second stage with a high water index enters the first-stage cyclic reaction from the middle reaction tank. The second-stage reaction is carried out in n series-connected reaction tanks with self-circulation and downward circulation, equipped with stirring and coil cooling, where n ≥ 3, and the volume V of the reaction tank is 100 - 120 m 3 , and the temperature in the terminal reaction tank is controlled to be 20 - 25 °C through the chilled water in the coils in the reaction tank, the chlorine index is 0.91 ± 0.01, and the water index is 22 ± 1;

[0015] (3) Return the salt mother liquor and the mother liquor of the second stage to the first-stage reaction tank according to a volume ratio of 3:1. Dissolve the glauber's salt containing glaserite and sodium sulfate in the salt mother liquor and the mother liquor of the second stage to obtain a nitrate solution. Control the potassium index of the mother liquor of the first stage to be 0.30 - 0.35, and the solid content to be 20% - 40%, so as to control the production amount of the glaserite generated at the end of the first-stage reaction.

[0016] Preferably, the content of K2O in the potassium sulfate product in the present invention is ≥50%.

[0017] Preferably, in step (1) of the present invention, the mass ratio of glauber's salt, potassium chloride, and water is 1:(1.0 - 1.1):(2.0 - 2.1), and most preferably 1:1.075:2.036.

[0018] Preferably, in step (2) of the present invention, the mass ratio of the flow rate of potassium chloride to the mass of glaserite is (2 - 2.5):1.

[0019] Preferably, in step (3) of the present invention, the mass ratio of the glauber's salt containing glaserite to sodium sulfate is (1 - 2):1.

[0020] The index in the present invention refers to the Jänecke index, which is mainly used in the research of water-salt phase diagrams and production guidance. The model drawing for the production of potassium sulfate from sodium sulfate is 2Na + 、2K + / / 2Cl - 、SO4 2-—H2O, representing the relationship between the physical phase and the composition. At any point in the phase diagram, the dry basis components (i.e., the concentrations of various ions) at that point can be understood, and this component representation is expressed using exponents. In the present invention, n 2Na+ +n 2K+ =n 2Cl- +n SO42- , and the proportion of each ion is called an exponent. For example, n 2Na+ =a, n 2K+ =b, n 2Cl- =C, n SO42- =d, n H2O =e, then the potassium exponent = a / (a + b), the water exponent = e / (a + b) = e / (c + d), and the chlorine exponent = c / (c + d).

[0021] The present invention designs a production process for preparing potassium sulfate by an asymmetric balanced method using potassium-containing mirabilite. This asymmetry includes many aspects: firstly, the evaporation system adopts a mode of multi-inlet of cold clear liquid (here, multi-inlet means more than the theoretical cold clear liquid entering) and multi-outlet of salt mother liquor (here, multi-outlet means more than the theoretical salt mother liquor produced), and evaporates according to a fixed ratio to obtain enough evaporation condensate water per unit time, and the extra part is used to digest the water supplemented into the system from the outside; secondly, since the two-stage conversion reaction is an equimolar reaction of potassium chloride solution and potassium-containing mirabilite, mirabilite containing potassium is used in combination with anhydrous sodium sulfate to produce potassium sulfate. The core is to control the index of the potassium exponent in the first-stage reaction system by using the proportion of mirabilite containing potassium, so as to adjust the production amount of potassium mirabilite to match the amount of evaporation condensate water that needs to be dissolved and consumed in an equimolar ratio, so as to maintain the overall balance of production, and at the same time, the quality of the prepared potassium sulfate meets the quality requirements of the national standard for agricultural potassium sulfate GB / T 20406-2017, powder crystalline excellent grade (K2O≥52%) and first grade (K2O≥50%).

[0022] Description of the Drawings

[0023] Figure 1 is a schematic process flow diagram of the present invention. Detailed Embodiments

[0024] The following further elaborates on the present invention in conjunction with embodiments for a clearer understanding of the present invention, but they do not constitute a limitation to the present invention.

[0025] In this embodiment, the front reaction tank of the first-stage conversion reaction refers to the first and second reaction tanks counted from left to right among the six tanks in the attached Figure 1 , the middle reaction tank of the first-stage conversion reaction refers to the third and fourth reaction tanks counted from left to right among the six tanks in the attached Figure 1 , and the end reaction tank refers to the fifth and sixth reaction tanks counted from left to right among the six tanks in the attached Figure 1 .

[0026] Example 1

[0027] See Figure 1 , a production process for preparing potassium sulfate by an asymmetric equilibrium method with potassium-containing mirabilite in this example includes the following steps:

[0028] (1) According to the material balance calculation at 25°C, sodium sulfate, potassium chloride and water are reacted in a mass ratio of 1:1.075:2.036 to obtain a first mother liquor and potassium-containing mirabilite, and the potassium-containing mirabilite enters the second conversion for reaction; after the first mother liquor is filtered by a plate and frame filter to remove impurities, condensate water is evaporated at a temperature of 100°C according to 30% of the total volume of the system to obtain salt and salt mother liquor, and the salt mother liquor undergoes n-stage flash evaporation to obtain a salt mother liquor with a low water content index, and after cooling to 50°C, it enters the front end of the first conversion reaction for recycling; the water content index of the first mother liquor in the reaction tank at the front end of the first conversion reaction is 14.20; the temperature of the first mother liquor in the middle reaction tank of the first conversion reaction is 35°C, and the water content index is 14.20. The temperature of the first mother liquor in the reaction tank at the end of the first conversion reaction is 30°C, and the water content index is 15.20; the first conversion reaction is n series-connected reaction tanks with self-circulation and downward circulation, equipped with stirring and coil cooling, n = 6, and the volume of the reaction tank V = 110m 3 , and the materials are continuously self-circulated and downward circulated through a circulating pump;

[0029] In the present invention, the function of the first conversion reaction is partitioned. No additional water is added in the reaction tanks in the first half, and the water content index of the first mother liquor at the front end is controlled to be 14.20; the quality of the potassium-containing mirabilite generated is controlled in the reaction tanks in the second half, and the residual Cl in the potassium-containing mirabilite - ≤3%.

[0030] (2) Potassium chloride is dissolved in the condensate water obtained in step (1) to obtain a potassium chloride solution, the mass fraction of potassium chloride in the potassium chloride solution is 24.7%, and the potassium chloride solution is subjected to a second conversion reaction with the potassium-containing mirabilite obtained in step (1). The potassium chloride solution is controlled by a flow meter, and the mass ratio of the flow rate of potassium chloride to the mass of potassium-containing mirabilite is 2:1 to obtain potassium sulfate and a second mother liquor. The second mother liquor with a high water content index enters the first conversion cycle reaction from the middle reaction tank; the second conversion reaction is n series-connected reaction tanks with self-circulation and downward circulation, equipped with stirring and coil cooling, where n = 3, and the volume of the reaction tank V = 110m 3 , and the temperature in the reaction tank at the end is controlled to be 23°C through the chilled water in the coil in the reaction tank, the chlorine index is 0.90, and the water content index is 21.20;

[0031] (3) Return the salt mother liquor and the secondary conversion mother liquor to the primary conversion reaction tank at a volume ratio of 3:1. Dissolve the potassium-containing mirabilite and sodium sulfate in the salt mother liquor and the secondary conversion mother liquor to obtain a nitrate solution. The mass ratio of the potassium-containing mirabilite to sodium sulfate is 1:1. Control the potassium index of the primary conversion mother liquor to be 0.30 and the solid content to be 25.6%, so as to control the production amount of potassium mirabilite generated at the end of the primary conversion reaction.

[0032] The content of K2O in the potassium sulfate product prepared in this example is 50.2%.

[0033] Example 2

[0034] See Figure 1 , a production process for preparing potassium sulfate by an asymmetric balanced method with potassium-containing mirabilite in this example, includes the following steps:

[0035] (1) According to the material balance calculation at 25 °C, react mirabilite, potassium chloride and water at a mass ratio of 1:1.1:2.1 to obtain a primary conversion mother liquor and potassium mirabilite. The potassium mirabilite enters the secondary conversion to participate in the reaction. After the primary conversion mother liquor is filtered through a plate and frame filter to remove impurities, condensate water is evaporated at a temperature of 100 °C at a ratio of 32% of the total volume of the system to obtain salt and salt mother liquor. The salt mother liquor undergoes n-stage flash evaporation to obtain a salt mother liquor with a low water content index, and then enters the front end of the primary conversion reaction for recycling after cooling to 55 °C. The water index of the primary conversion mother liquor in the front-end reaction tank of the primary conversion reaction is 14.80. The temperature of the primary conversion mother liquor in the middle reaction tank of the primary conversion reaction is 33 °C, and the water index is 14.80. The temperature of the primary conversion mother liquor in the reaction tank at the end of the primary conversion reaction is 28 °C, and the water index is 15.80. Among them, the primary conversion reaction is n series-connected reaction tanks with self-circulation and down-circulation, equipped with stirring and coil cooling, n = 6, and the volume of the reaction tank V = 110m 3 , and the material continuously undergoes self-circulation and down-circulation through a circulation pump;

[0036] In the present invention, the functions of the primary conversion reaction are partitioned. No additional water is added in the reaction tanks in the first half, and the water index of the primary conversion mother liquor at the front end is controlled to be 14.80. The quality of the potassium mirabilite generated is controlled in the reaction tanks in the second half, and the residual Cl- in the potassium mirabilite is ≤3%.

[0037] (2) Dissolve potassium chloride in the condensate water obtained in step (1) to obtain a potassium chloride solution. The mass fraction of potassium chloride in the potassium chloride solution is 24.8%. Perform a secondary conversion reaction on the potassium chloride solution and the potassium mirabilite obtained in step (1). The potassium chloride solution is controlled by a flow meter, and the mass ratio of the flow rate of potassium chloride to the mass of potassium mirabilite is 2.5:1 to obtain potassium sulfate and a secondary conversion mother liquor. The secondary conversion mother liquor with a high water content index enters the primary conversion cycle reaction from the middle reaction tank. Among them, the secondary conversion reaction is n series-connected reaction tanks with self-circulation and down-circulation, equipped with stirring and coil cooling, where n = 3 and the volume of the reaction tank V = 110m3 , the temperature inside the reaction tank is lowered by the chilled water in the coil, and the temperature inside the terminal reaction tank is controlled at 22 °C, the chlorine index is 0.91, and the water index is 22.50;

[0038] (3) The salt mother liquor and the secondary conversion mother liquor are returned to the primary conversion reaction tank according to a volume ratio of 3:1. The mirabilite containing potassium and the sodium sulfate are dissolved in the salt mother liquor and the secondary conversion mother liquor to obtain a nitrate solution. The mass ratio of the mirabilite containing potassium to the sodium sulfate is 2:1. The potassium index of the primary conversion mother liquor is controlled at 0.33, and the solid content is 33%, so as to control the production amount of potassium mirabilite generated at the end of the primary conversion reaction.

[0039] The content of K2O in the potassium sulfate product prepared in this example is 52.3%.

[0040] Example 3

[0041] See Figure 1 , a production process for preparing potassium sulfate by an asymmetric balance method of potassium-containing mirabilite in this example, including the following steps:

[0042] (1) According to the material balance calculation at 25 °C, mirabilite, potassium chloride and water are added in a mass ratio of 1:1:2 for reaction to obtain a primary conversion mother liquor and potassium mirabilite, and the potassium mirabilite enters the secondary conversion for reaction; after the primary conversion mother liquor is filtered through a plate and frame to remove impurities, the condensed water is evaporated at a temperature of 100 °C according to 35% of the total volume of the system to obtain salt and salt mother liquor. The salt mother liquor undergoes n-stage flash evaporation to obtain a salt mother liquor with a low water index, and after cooling to 58 °C, it enters the front end of the primary conversion reaction for recycling; the water index of the primary conversion mother liquor in the front-end reaction tank of the primary conversion reaction is 14.50; the temperature of the primary conversion mother liquor in the middle reaction tank of the primary conversion reaction is 34 °C, the water index is 14.50, and the temperature of the primary conversion mother liquor in the reaction tank at the end of the primary conversion reaction is 27 °C, the water index is 15.50; the primary conversion reaction is n series-connected reaction tanks with self-circulation and down-circulation, equipped with stirring and coil cooling, n = 6, and the volume of the reaction tank V = 110m 3 , and the material continuously circulates and circulates downward through the circulation pump;

[0043] In the present invention, the function of the primary conversion reaction is partitioned. No additional water is added in the reaction tanks in the first half, and the water index of the front-end primary conversion mother liquor is controlled at 14.50; the quality of the potassium mirabilite generated is controlled in the reaction tanks in the second half, and the residual Cl- in the potassium mirabilite ≤ 3%.

[0044] (2) Dissolve potassium chloride in the condensed water obtained in step (1) to obtain a potassium chloride solution. The mass fraction of potassium chloride in the potassium chloride solution is 24%-26%. Carry out a second-stage conversion reaction between the potassium chloride solution and the glaserite obtained in step (1). The potassium chloride solution is controlled by a flow meter. The mass ratio of the flow rate of potassium chloride to the mass of glaserite is 2.2:1 to obtain potassium sulfate and second-stage conversion mother liquor. The second-stage conversion mother liquor with a high water content index enters the first-stage circulation reaction from the middle reaction tank; the second-stage conversion reaction is carried out in n series-connected reaction tanks with self-circulation and down-circulation, equipped with stirring and coil cooling, where n = 3 and the volume of the reaction tank V = 110m 3 , and the temperature is lowered by the chilled water in the coil in the reaction tank. The temperature in the terminal reaction tank is controlled at 23°C, the chlorine index is 0.90, and the water index is 21.8;

[0045] (3) Return the salt mother liquor and the second-stage conversion mother liquor to the first-stage reaction tank according to a volume ratio of 3:1. Dissolve the glauberite containing glaserite and anhydrous sodium sulfate in the salt mother liquor and the second-stage conversion mother liquor to obtain a nitrate solution. The mass ratio of the glauberite containing glaserite to anhydrous sodium sulfate is 1.5:1. Control the potassium index of the first-stage conversion mother liquor to be 0.32 and the solid content to be 28% to control the production amount of glaserite generated at the end of the first-stage conversion reaction.

[0046] The content of K2O in the potassium sulfate product prepared in this example is 50.8%.

Claims

1. A production process for preparing potassium sulfate by an asymmetric balancing method using potassium-containing mirabilite, characterized in that, It includes the following steps: (1) According to the material balance calculation at 25 °C, mirabilite, potassium chloride and water are added in proportion to react, obtaining a first mother liquor and glaserite, and the glaserite enters the second reaction stage to participate in the reaction; after the first mother liquor is filtered through a plate and frame filter to remove impurities, condensate water is evaporated at a temperature of 100 °C in a proportion of 30-35% of the total volume of the system, obtaining salts and a salt mother liquor. The salt mother liquor undergoes n-stage flash evaporation to obtain a salt mother liquor with a low water content index. After cooling to 50-60 °C, it enters the front end of the first reaction stage for recycling; the water content index of the first mother liquor in the reaction tank at the front end of the first reaction stage is 14-15; the temperature of the first mother liquor in the middle reaction tank of the first reaction stage is 25-35 °C, and the water content index is 14-15. The temperature of the first mother liquor in the reaction tank at the end of the first reaction stage is 25-35 °C, and the water content index is 15-16; the first reaction is n series-connected reaction tanks with self-circulation and down-circulation, equipped with stirring and coil cooling, where n ≥ 6 and the volume of the reaction tank V = 100-120m 3 , and the material continuously undergoes self-circulation and down-circulation through a circulation pump; (2) Dissolve potassium chloride in the condensed water obtained in step (1) to obtain a potassium chloride solution, where the mass fraction of potassium chloride in the potassium chloride solution is 24%-26%. React the potassium chloride solution with the glaserite obtained in step (1) in a second conversion reaction. The potassium chloride solution is controlled by a flow meter to obtain potassium sulfate and a second conversion mother liquor. The second conversion mother liquor with a high water content index enters the first conversion circulation reaction from the middle reaction tank; the second conversion reaction is carried out in n series-connected reaction tanks with self-circulation and down-circulation, equipped with stirring and coil cooling, where n≥3 and the volume V of the reaction tank is 100-120m 3 , and the temperature inside the reaction tank is lowered by the chilled water in the coil inside the reaction tank. The temperature inside the terminal reaction tank is controlled at 20-25°C, the chlorine index is 0.91±0.01, and the water index is 22±1; (3) Return the mother liquor of salt and the mother liquor of the second conversion to the first conversion reaction tank according to a volume ratio of 3:1, dissolve the mirabilite and sodium sulfate containing potassium mirabilite in the mother liquor of salt and the mother liquor of the second conversion to obtain a nitrate solution, and control the potassium index of the mother liquor of the first conversion to be 0.30 - 0.35 and the solid content to be 20% - 40%, so as to control the production amount of potassium mirabilite generated at the end of the first conversion reaction.

2. The production process for preparing potassium sulfate by an asymmetric balancing method using potassium-containing mirabilite according to claim 1, characterized in that: The content of K2O in the potassium sulfate product is ≥50%.

3. The production process for preparing potassium sulfate by an asymmetric balancing method using potassium-containing mirabilite as claimed in claim 1, characterized in that: In the step (1), the mass ratio of mirabilite, potassium chloride and water is 1:(1.0 - 1.1):(2.0 - 2.1).

4. The production process for preparing potassium sulfate by an asymmetric balance method using potassium mirabilite according to claim 1, characterized in that: In the step (2), the mass ratio of the flow rate of potassium chloride to the mass of potassium mirabilite is (2 - 2.5):

1.

5. The production process for preparing potassium sulfate by an asymmetric balancing method using potassium-containing mirabilite as claimed in claim 1, characterized in that: In the step (3), the mass ratio of mirabilite containing potassium mirabilite to sodium sulfate is (1 - 2):1.

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