Coarse salt purification equation and steps, coarse salt purification equation

Coarse salt contains more soluble impurities (CaCl2, MgCl2, etc.) and insoluble impurities (sediment, etc.). How can refined salt be produced?

To remove soluble impurities, one or several chemical reagents are generally selected to react these soluble impurities, and no new impurities can be generated. The removal of insoluble impurities is generally achieved through three steps: dissolution, filtration, and evaporation.

The coarse salt weighed before the experiment should not be too much, otherwise there will be a surplus phenomenon, which will affect the quality of purification. When dissolving, pay attention to stirring in time so that the coarse salt can completely dissolve into the water.

When filtering, we should pay attention to "one stick, two low, and three leaning". It is recommended to let it sit for a while before filtration, let the upper filtrate filter through before pouring the solution mixed with sediment into the funnel. If you pour them together, it will cause the filter paper to clog and slow down the filtration speed.

Steps: Add BACL2 to produce a white precipitate, stop when the white precipitate no longer increases, consider the precipitate BaSO4, and remove the impurity SO42-;

Na2CO3 was added to produce a white precipitate, which was stopped when the white precipitate no longer increased, and the precipitated CaCO3 was considered and the impurity Ca2+ was removed;

NaOH is added to produce a white precipitate, and the white precipitate is stopped when it no longer increases, and the precipitate Mg(OH)2 and Ba(OH)2 are considered

Finally, HCl is added until the solution is neutral.

Coarse salt often contains Ca2+, Mg2+, SO42-, and the steps of purification are as follows.

1. Add a sufficient amount of BaCl2 solution first, remove SO42-, BA2+SO42-=BASO4

2. Add a sufficient amount of NaOH solution to remove Mg2+, Mg2+2OH-=Mg(OH)2

3. Add a sufficient amount of Na2CO3 solution to remove Ca2+, Ca2+CO32-=CaCO3

4. Filtration. 5. Add an appropriate amount of HCl to the filtrate

Add excess BaCl2: BaCl2+Na2SO4=BaSO4 +2NaCl; Add excess NaOH: MgCl2+2NaOH = Mg(OH)2+2NaCl; Add an excess of Na2CO3:

na2co3+cacl2=caco3↓+2nacl;na2co3+bacl2=baco3↓+2nacl。

Steps and equations for coarse salt purification

Weigh 2 grams of coarse salt (to the nearest gram) on a tray balance. Measure 10 ml of water with a graduated cylinder and pour it into a beaker. Take a spoonful of coarse salt with a medicine spoon and add it to the water, and stir it with a glass rod to observe the phenomenon (what is the effect of the stirring of the glass rod on the dissolution of coarse salt?)

stir to speed up the dissolution). Then add the coarse salt and stir with a glass rod as you add until the coarse salt is no longer dissolved. Observe if the solution becomes cloudy.

1.Weigh the remaining coarse salt on a balance and calculate approximately how many grams of coarse salt has been dissolved in 10 ml of water;

2.Add excess BaCl2 (remove sulfate ions) BaCl2 + Na2SO4 = BaSO4 + 2NaCl;

3.Add excess NaOH (remove magnesium ions) MgCl2 + 2NaOH = Mg(OH)2 + 2NaCl;

4.Add excess Na2CO3 (remove calcium ions and barium residual mode ions in BaCl2) Na2CO3 + CaCl2 = CaCO3 + 2NaCl;

Note: Interchangeable 2,3 two-step or 3,4-step. The dosage of Na2CO3 must remove all BaCl2, and the amount can be controlled by using pH test strips. )

6.Filtration: add an appropriate amount of HCl to the filtrate (remove excess NaOH and Na2CO3, you can choose to control the amount added with pH test paper, or direct evaporation);

7.Evaporation crystallization.