Solubility of potassium sulfate and zinc sulfate
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This post was last edited by Luan Suo Suan Suo on 2009-7-29 at 21:57. Potassium sulfate and zinc sulfate – I conducted a comparison of their solubility today. The room temperature was between 25 and 28 degrees Celsius. When 5 grams of potassium sulfate were added to 100 grams of water and stirred, a white turbidity appeared; adding another 100 grams of water and stirring further reduced the turbidity, and with slight heating the solution became transparent. When 5 grams of zinc sulfate were added to 100 grams of water and stirred, a white turbid substance formed; adding another 100 grams of water and stirring still resulted in turbidity, and upon heating, flocculent-like substances appeared on the surface of the liquid. K2SO4 used: K2O >= 50%, pH 3~4, CL
Potassium sulfate produced by the Mannheim method (the other methods are not known) can have an oxidation potassium content of up to 51–51.5% at the time of completion of production; **the standard requirement is that this value be above 50%. Since an excess of acid is used in the production process, the final product contains free acid. Generally, manufacturers add a certain amount of limestone powder to neutralize this free acid, which also helps to reduce the oxidation potassium content (while keeping it above 50%), thereby lowering production costs. The main component of stone powder is calcium carbonate, and calcium sulfate, which is formed when it reacts with sulfuric acid, is slightly soluble; that’s why the dissolution process results in the phenomenon you see. As for zinc sulfate, I’m not familiar with it, but given that the ZnSO4 content is >=94.7% according to what you’ve provided, there must be 5.3% of other components. If those other components are insoluble substances, then the situation you described could occur. Is it similar to the production of potassium sulfate, where additional additives are added to reduce costs while still maintaining quality?
2# yulin1973: Thank you to the friend from the second floor. The K2SO4 powder I use may contain additives; however, no caking has occurred after it has been stored for over a month.
Potassium sulfate has low hygroscopicity and generally does not caking; additives are added mainly to neutralize free acids, otherwise the level of free acids will exceed the acceptable limit
2# yulin1973: ZnSO4 >= 94.7, as this is zinc sulfate monohydrate; however, the content is calculated based on zinc sulfate
4# yulin1973 So, what is the water solubility of K2SO4 produced by other methods? Is there no specification regarding the water solubility of K2SO4 in the current GB standards?
The agricultural potassium sulfate standard does not specify solubility. The Mannheim process is the most mature method for producing potassium sulfate, and over 70% of potassium sulfate produced in China is manufactured using this method. Among other methods, only the double-displacement method has been put into large-scale production. This method involves reacting potassium chloride with salts containing sulfate ions to produce double salts, yielding potassium sulfate as a product along with by-products. However, due to the characteristics of double-displacement reactions, the double salts generally cannot be completely decomposed, which results in poor product quality. Solubility also varies somewhat depending on the raw materials used.
I tried it today: I added 5 grams per 100 milliliters of sodium carbonate solution to the already dissolved K2SO4 solution, and a white turbidity appeared. When 1:3 hydrochloric acid was added, bubbles formed and the turbidity disappeared, leaving the solution clear. It seems that K2SO4 contains slightly soluble calcium sulfate
There is not only calcium sulfate, but also a small amount of unreacted calcium carbonate
The zinc sulfate solution contains white flocculent particles, which may be due to a too high pH value of the solution, causing hydrolysis of zinc sulfate
Perhaps the person who conducted the experiment was too hasty; being more patient might yield results that are closer to those in the literature! \!