Experimental procedure for crude salt purification in chemical experiments

1.Dissolve 2Filter 3Evaporation 4Calculate the yield (what the chemistry teacher said.)

Dissolving, precipitation, filtration, evaporation crystallization.

Dissolve, filter, evaporate, calculate yield.

Weighing, dissolving, evaporating, crystallizing.

Principle: Coarse salt contains insoluble impurities such as sediment, as well as soluble impurities such as Ca2+, Mg2+, SO42-, etc.

Insoluble impurities can be removed by filtration, Ca2+, Mg2+, SO42- in soluble impurities can be removed by adding BaCl2, NaOH and Na2CO3 solutions to generate precipitate, or BaCO3 solid and NaOH solution can be added to remove, and then evaporate water to obtain purer refined salt.

Steps: Dissolve: (Weigh about 4 grams of coarse salt and add it to a 12ml beaker) stir with a glass rod to accelerate dissolution. The liquid is cloudy and has sediment.

Filtration: Adjust the iron ring to the appropriate position and place the beaker and strainer. The glass rod is leaning against the three-layer filter paper, the lower end of the funnel is close to the inner wall of the beaker, the beaker nozzle is leaning against the glass rod for drainage, and the edge of the liquid level is lower than the edge of the filter paper (the filter paper should be close to the funnel when making the filter), and if the filtrate is turbid, it can be filtered again.

The clarified filtrate is filtered out and the insoluble matter remains on the filter paper.

HCL is added first, followed by excess BaCl2

White precipitate baso4 appears

bacl2+naso4= baso4↓+nacl

Filtration: Add excess Na2CO3 again

White precipitate baco3 caco3 appears

na2co3+ bacl2= baco3↓+nacl

na2co3+ca(oh)2= caco3↓+h2o+co2↑

Filter: Add excess NaOH again

White precipitate Mg(OH)2 appears

naoh+mgcl2= mg(oh)2↓+nacl

Filter and then add HCl

Bubbles emerge HCl+ Na2CO3= NaCl+H2O+CO2

hcl+naoh= nacl+h2o

Experimental conclusion: There are not only insoluble substances such as sediment but also soluble substances such as mgcl2, bacl2 sulfate and so on in coarse salt.

Step 1: Dissolve: Weigh about 4 grams of coarse salt and add 12 milligrams.

, and there is. Stir.

Objective: To make NaCl, MgCl2, CaCl2, Na2SO4, etc. soluble in water.

2 Filtration: Place the coarse brine alongside. Into. Middle.

Objective: To remove insoluble impurities from coarse salt.

3. Evaporation: pour the obtained clarified filtrate in.

Medium, put. Placed.

On the iron hoop, use.

Heat and use at the same time.

Stir the filtrate constantly.

Objective: To obtain solid table salt from solution.

1. Experimental procedure: dissolution, filtration, evaporation.

Second, the role of the glass rod:

1) Stir when dissolving to speed up dissolution.

2) Drain when filtering.

3) When evaporating, stir to make the heating even.

Third, the key points to note in filtration: one stick, two low, three leaning.

Fourth, the key points in evaporation: stirring the glass rod and evaporating the filtrate with waste heat.

Take a small amount of coarse salt and add it.

medium, add an appropriate amount of water, stir with a glass rod, wait for the coarse salt to be fully dissolved, and pour the turbid salt water along the glass rod into the installed one.

, and then the resulting filtrate in.

Medium heating until a large amount of solids appears in the filtrate, and the heating is stopped.